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134-525: The vaquita ( / v ə ˈ k iː t ə / və- KEE -tə ; Phocoena sinus ) is a species of porpoise endemic to the northern end of the Gulf of California in Baja California , Mexico . Reaching a maximum body length of 150 cm (4.9 ft) (females) or 140 cm (4.6 ft) (males), it is the smallest of all living cetaceans . The species is currently on the brink of extinction , and

268-423: A mutation–selection balance . It is predicted that a viral quasispecies at a low but evolutionarily neutral and highly connected (that is, flat) region in the fitness landscape will outcompete a quasispecies located at a higher but narrower fitness peak in which the surrounding mutants are unfit, "the quasispecies effect" or the "survival of the flattest". There is no suggestion that a viral quasispecies resembles

402-400: A "classical" method of determining species, such as with Linnaeus, early in evolutionary theory. However, different phenotypes are not necessarily different species (e.g. a four-winged Drosophila born to a two-winged mother is not a different species). Species named in this manner are called morphospecies . In the 1970s, Robert R. Sokal , Theodore J. Crovello and Peter Sneath proposed

536-424: A 'smallest clade' idea" (a phylogenetic species concept). Mishler and Wilkins and others concur with this approach, even though this would raise difficulties in biological nomenclature. Wilkins cited the ichthyologist Charles Tate Regan 's early 20th century remark that "a species is whatever a suitably qualified biologist chooses to call a species". Wilkins noted that the philosopher Philip Kitcher called this

670-410: A bill introduced to improve the management of driftnets , with gillnets being under the umbrella of this fishing tool. The bill's focus is to ban the use of large-scale nets while supporting the use of alternative methods of fishing to decrease the maximum amount of bycatch . There is also a compensation plan proposed in the bill for fishery participants who stop using large-scale nets. Gillnets are

804-428: A connected series of neighbouring populations, each of which can sexually interbreed with adjacent related populations, but for which there exist at least two "end" populations in the series, which are too distantly related to interbreed, though there is a potential gene flow between each "linked" population. Such non-breeding, though genetically connected, "end" populations may co-exist in the same region thus closing

938-517: A controversial gear type especially among sport fishers who argue they are inappropriate especially for salmon fisheries. These arguments are often related to allocation issues between commercial and recreational (sport) fisheries and not conservation issues. Most salmon fisheries, especially those targeting Pacific salmon in North America, are strictly managed to minimize total impacts to specific populations and salmon fishery managers continue to allow

1072-642: A deleterious effect on vaquitas. Bycatch, which is the incidental catch of non-target species in fishing gear, is not only the largest threat to the survival of the vaquita, but to all marine mammals around the world. A series of simulations in a 2022 study indicate that the species has a chance to survive and recover if all bycatch is halted, despite the presence of other threats. However, the biggest threat still towards vaquita are fisheries. Northern fishing fleets have had an indirect positive impact mainly on marine mammals, because fishing on predators like sharks reduces its predatory negative impact on those groups. Although

1206-432: A different species from its ancestors. Viruses have enormous populations, are doubtfully living since they consist of little more than a string of DNA or RNA in a protein coat, and mutate rapidly. All of these factors make conventional species concepts largely inapplicable. A viral quasispecies is a group of genotypes related by similar mutations, competing within a highly mutagenic environment, and hence governed by

1340-689: A felony to remove an endangered species. Alongside this, the Government of Mexico also made a public agreement to prohibit gillnet use. Efforts are proactive in incentive applications to fisheries in a system of trade-offs that benefit fishermen and the vaquita. Mexico launched a program in 2008 called PACE-VAQUITA in an effort to enforce the gillnet ban in the Biosphere Reserve, allow fishermen to swap their gillnets for vaquita-safe fishing gear, and provide economic support to fishermen for surrendering fishing permits and pursuing alternative livelihoods. Despite

1474-508: A genetic boundary suitable for defining a species concept is present. DNA barcoding has been proposed as a way to distinguish species suitable even for non-specialists to use. One of the barcodes is a region of mitochondrial DNA within the gene for cytochrome c oxidase . A database, Barcode of Life Data System , contains DNA barcode sequences from over 190,000 species. However, scientists such as Rob DeSalle have expressed concern that classical taxonomy and DNA barcoding, which they consider

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1608-406: A high degree of size selectivity. Most salmon fisheries in particular have an extremely low incidence of catching non-target species. A fishing vessel rigged to fish by gillnetting is a gillnetter . A gillnetter which deploys its gillnet from the bow is a bowpicker , while one which deploys its gillnet from the stern is a sternpicker . Gillnets differ from seines in that the latter uses

1742-569: A kilogram of totoaba swim bladders, with some making as much as $ 116,000 in one day. The swim bladders of the Totoaba macdonaldi are being sold on the black market by cartel for profit. With continued illegal totoaba fishing, which is largely motivated by sales to the Chinese market where it is used in traditional medicine , and uncontrolled bycatch of vaquitas, the International Committee for

1876-465: A lineage should be divided into multiple chronospecies , or when populations have diverged to have enough distinct character states to be described as cladistic species. Species and higher taxa were seen from the time of Aristotle until the 18th century as categories that could be arranged in a hierarchy, the great chain of being . In the 19th century, biologists grasped that species could evolve given sufficient time. Charles Darwin 's 1859 book On

2010-541: A maximum of 9 to 11), the lowest ever count, but this number may just be a result of the small survey area instead of an actual population decline, as vaquitas freely move in and out of the survey region. Vaquitas reach sexual maturity from three to six years old. Vaquitas have synchronous reproduction, suggesting that calving span is greater than a year. Their pregnancies last from 10 to 11 months, and vaquita calves are nursed by their mothers for 6–8 months until becoming independent. Vaquitas give birth about every other year to

2144-492: A misnomer, need to be reconciled, as they delimit species differently. Genetic introgression mediated by endosymbionts and other vectors can further make barcodes ineffective in the identification of species. A phylogenetic or cladistic species is "the smallest aggregation of populations (sexual) or lineages (asexual) diagnosable by a unique combination of character states in comparable individuals (semaphoronts)". The empirical basis – observed character states – provides

2278-416: A net and passes only part way through the mesh. When it struggles to free itself, the twine slips behind the gill cover and prevents escape. Gillnets are so effective that their use is closely monitored and regulated by fisheries management and enforcement agencies. Mesh size , twine strength, as well as net length and depth are all closely regulated to reduce bycatch of non-target species. Gillnets have

2412-449: A particular species, including which genus (and higher taxa) it is placed in, is a hypothesis about the evolutionary relationships and distinguishability of that group of organisms. As further information comes to hand, the hypothesis may be corroborated or refuted. Sometimes, especially in the past when communication was more difficult, taxonomists working in isolation have given two distinct names to individual organisms later identified as

2546-400: A perfect model of life, it is still a useful tool to scientists and conservationists for studying life on Earth, regardless of the theoretical difficulties. If species were fixed and clearly distinct from one another, there would be no problem, but evolutionary processes cause species to change. This obliges taxonomists to decide, for example, when enough change has occurred to declare that

2680-403: A population in captivity have proved to be more threatening to the population than helpful. A November 2017 effort ended up traumatizing and killing one female vaquita, as well as invoking unnecessary stress onto a juvenile. Still, creating a captive population could be used as a last resort to save the species and to further educate on vaquitas. The vaquita is listed as critically endangered on

2814-617: A relatively low release mortality rate on salmon and steelhead released from these small mesh gillnets. Problems that can arise from selective harvesting are smaller reproducing adult fish, as well as the unexpected mortality of the fish which sustain injuries from the gillnet but are not retained in the fishery. Most salmon populations include several age classes , allowing for fish of different ages, and sizes, to reproduce with each other. A recent 2009 study looked at 59 years of catch and escapement data of Bristol Bay sockeye salmon to determine age and size at maturity trends attributable to

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2948-529: A result the population has continued to decline. Fewer than 19 vaquitas remained in the wild in 2018. Large-mesh gillnets used in illegal fishing for totoaba caused an increase in the rate of loss of vaquitas after 2011. In 2021, the Mexican government eliminated a "no tolerance" zone in the Upper Gulf of California and opened it up to fishing. In 2022 the navy began to place concrete blocks with rebar hooks into what

3082-437: A rise in commercial fishing such as accidental by-catch, illegal fishing, and entanglement have been linked to the cause of their decline. Shrimp fishing and gillnets create entanglement issues for the vaquita. Aspects of illegal fishing include open access fisheries and absent fisheries management have correlated towards poaching of the main prey source of the vaquita. The swim bladders of the Totoaba macdonaldi are being sold on

3216-438: A rounded head, and no distinguished beak. The coloration is mostly grey with a darker back and a white ventral field. Prominent black patches surround its lips and eyes. Sexual dimorphism is apparent in body size, with mature females being longer than males and having larger heads and wider flippers. Females reach a maximum size of about 150 cm (4.9 ft), while males reach about 140 cm (4.6 ft). Dorsal fin height

3350-453: A series of panels of meshes with a weighted "foot rope" along the bottom, and a headline , to which floats are attached. By altering the ratio of floats to weights, buoyancy changes, and the net can therefore be set to fish at any depth in the water column. In commercial fisheries, the meshes of a gillnet are uniform in size and shape. Fish smaller than the mesh of the net pass through unhindered, while those too large to push their heads through

3484-400: A short way of saying that something applies to many species within a genus, but not to all. If scientists mean that something applies to all species within a genus, they use the genus name without the specific name or epithet. The names of genera and species are usually printed in italics . However, abbreviations such as "sp." should not be italicised. When a species' identity is not clear,

3618-456: A single calf, usually between the months of February and April. Because of their low reproduction rates, long gestation periods and larger species size, vaquitas are considered a K -selected species. K -selected species are more vulnerable to extinction as they cannot repopulate at the rate of r -selected species. Vaquitas are on the brink of extinction because their numbers are few and they cannot replenish their population fast enough to exceed

3752-407: A single netting wall kept vertical by a floatline (upper line/headrope) and a weighted groundline (lower line/footrope). Small floats , usually shaped like eggs or cylinders and made of solid plastic, are evenly distributed along the floatline, while lead weights are evenly distributed along groundline. The lower line can also be made of lead cored rope, which does not need additional weight. The net

3886-404: A specialist may use "cf." before the epithet to indicate that confirmation is required. The abbreviations "nr." (near) or "aff." (affine) may be used when the identity is unclear but when the species appears to be similar to the species mentioned after. With the rise of online databases, codes have been devised to provide identifiers for species that are already defined, including: The naming of

4020-523: A species as groups of actually or potentially interbreeding natural populations, which are reproductively isolated from other such groups. It has been argued that this definition is a natural consequence of the effect of sexual reproduction on the dynamics of natural selection. Mayr's use of the adjective "potentially" has been a point of debate; some interpretations exclude unusual or artificial matings that occur only in captivity, or that involve animals capable of mating but that do not normally do so in

4154-400: A species as determined by a taxonomist. A typological species is a group of organisms in which individuals conform to certain fixed properties (a type), so that even pre-literate people often recognise the same taxon as do modern taxonomists. The clusters of variations or phenotypes within specimens (such as longer or shorter tails) would differentiate the species. This method was used as

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4288-488: A species. All species definitions assume that an organism acquires its genes from one or two parents very like the "daughter" organism, but that is not what happens in HGT. There is strong evidence of HGT between very dissimilar groups of prokaryotes , and at least occasionally between dissimilar groups of eukaryotes , including some crustaceans and echinoderms . The evolutionary biologist James Mallet concludes that there

4422-685: A species. Generally the term includes the unknown element of a distinct act of creation. Many authors have argued that a simple textbook definition, following Mayr's concept, works well for most multi-celled organisms , but breaks down in several situations: Species identification is made difficult by discordance between molecular and morphological investigations; these can be categorised as two types: (i) one morphology, multiple lineages (e.g. morphological convergence , cryptic species ) and (ii) one lineage, multiple morphologies (e.g. phenotypic plasticity , multiple life-cycle stages). In addition, horizontal gene transfer (HGT) makes it difficult to define

4556-519: A taxonomic decision at the discretion of cognizant specialists, is not governed by the Codes of Zoological or Botanical Nomenclature, in contrast to the PhyloCode , and contrary to what is done in several other fields, in which the definitions of technical terms, like geochronological units and geopolitical entities, are explicitly delimited. The nomenclatural codes that guide the naming of species, including

4690-484: A tighter weave to trap fish in an enclosed space, rather than directly catching the fish as in a gillnet. Gillnets existed in ancient times, as archaeological evidence from the Middle East demonstrates. In North America, Native American fishermen used cedar canoes and natural fibre nets, e.g., made with nettles or the inner bark of cedar. They would attach stones to the bottom of the nets as weights, and pieces of wood to

4824-506: A traditional biological species. The International Committee on Taxonomy of Viruses has since 1962 developed a universal taxonomic scheme for viruses; this has stabilised viral taxonomy. Most modern textbooks make use of Ernst Mayr 's 1942 definition, known as the Biological Species Concept as a basis for further discussion on the definition of species. It is also called a reproductive or isolation concept. This defines

4958-447: A variation on the morphological species concept, a phenetic species, defined as a set of organisms with a similar phenotype to each other, but a different phenotype from other sets of organisms. It differs from the morphological species concept in including a numerical measure of distance or similarity to cluster entities based on multivariate comparisons of a reasonably large number of phenotypic traits. A mate-recognition species

5092-408: A variety of demersal fish species, crustaceans , and squids , though benthic fish such as grunts and croakers make up most of the diet. Vaquitas are generally seen alone or in pairs, often with a calf, but have been observed in small groups of up to 10 individuals. Little is known about the life history of this species. Life expectancy is estimated at about 20 years and age of sexual maturity

5226-515: A variety of reasons. Viruses are a special case, driven by a balance of mutation and selection , and can be treated as quasispecies . Biologists and taxonomists have made many attempts to define species, beginning from morphology and moving towards genetics . Early taxonomists such as Linnaeus had no option but to describe what they saw: this was later formalised as the typological or morphological species concept. Ernst Mayr emphasised reproductive isolation, but this, like other species concepts,

5360-599: A year after loss , while others have found lost nets destroyed by wave action within one month or overgrown with seaweeds , increasing their visibility and reducing their catching potential to such an extent that they became a microhabitat used by small fish. This type of net was heavily used by many Japanese , South Korean , and Taiwanese fishing fleets on the high seas in the 1980s to target tunas . Although highly selective with respect to size class of animals captured, gillnets are associated with high numbers of incidental captures of cetaceans ( whales and dolphins ). In

5494-493: Is ghost fishing by lost nets and bycatch of diving seabirds. Nets combined in this way were first used in the Mediterranean. A drift net consists of one or more panels of webbing fastened together. They are left free to drift with the current, usually near the surface or not far below it. Floats on the floatline and weights on the groundline keep them vertical. Drift nets drift with the current while they are connected with

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5628-438: Is "an entity composed of organisms which maintains its identity from other such entities through time and over space, and which has its own independent evolutionary fate and historical tendencies". This differs from the biological species concept in embodying persistence over time. Wiley and Mayden stated that they see the evolutionary species concept as "identical" to Willi Hennig 's species-as-lineages concept, and asserted that

5762-400: Is a group of sexually reproducing organisms that recognise one another as potential mates. Expanding on this to allow for post-mating isolation, a cohesion species is the most inclusive population of individuals having the potential for phenotypic cohesion through intrinsic cohesion mechanisms; no matter whether populations can hybridise successfully, they are still distinct cohesion species if

5896-458: Is a set of organisms adapted to a particular set of resources, called a niche, in the environment. According to this concept, populations form the discrete phenetic clusters that we recognise as species because the ecological and evolutionary processes controlling how resources are divided up tend to produce those clusters. A genetic species as defined by Robert Baker and Robert Bradley is a set of genetically isolated interbreeding populations. This

6030-440: Is always an option for conservationists, but because the vaquita's range is so small, there would be no use in trying to establish habitat corridors . One option for conservationists could be trying to create buffer zones near the coast in which pesticides harmful to vaquitas are restricted or even unavailable in order to enhance the protection value of the vaquita's range. In May 2023, a wildlife survey expedition discovered that

6164-414: Is called speciation . Charles Darwin was the first to describe the role of natural selection in speciation in his 1859 book The Origin of Species . Speciation depends on a measure of reproductive isolation , a reduced gene flow. This occurs most easily in allopatric speciation, where populations are separated geographically and can diverge gradually as mutations accumulate. Reproductive isolation

6298-412: Is called the specific name or the specific epithet (in botanical nomenclature , also sometimes in zoological nomenclature ). For example, Boa constrictor is one of the species of the genus Boa , with constrictor being the species' epithet. While the definitions given above may seem adequate at first glance, when looked at more closely they represent problematic species concepts. For example,

6432-587: Is considered the primary area for vaquita, which was designated as a zero tolerance area (ZTA) for fishing in 2020. These are known to destroy gillnets (which can cost tens of thousands of dollars) in shallower waters. Their deployment had an immediate effect on the number of fishing boats in the area. Citing reports of echolocation outside of the ZTA, the navy expanded the area in which these blocks were placed starting in November 2023 with plans to continue placing new blocks until

6566-403: Is described formally, in a publication that assigns it a unique scientific name. The description typically provides means for identifying the new species, which may not be based solely on morphology (see cryptic species ), differentiating it from other previously described and related or confusable species and provides a validly published name (in botany) or an available name (in zoology) when

6700-671: Is further weakened by the existence of microspecies , groups of organisms, including many plants, with very little genetic variability, usually forming species aggregates . For example, the dandelion Taraxacum officinale and the blackberry Rubus fruticosus are aggregates with many microspecies—perhaps 400 in the case of the blackberry and over 200 in the dandelion, complicated by hybridisation , apomixis and polyploidy , making gene flow between populations difficult to determine, and their taxonomy debatable. Species complexes occur in insects such as Heliconius butterflies, vertebrates such as Hypsiboas treefrogs, and fungi such as

6834-535: Is greater in males than in females. They are also known to weigh around 27 kg (60 lb) to 68 kg (150 lb). This makes them one of the smallest species in the porpoise family. Vaquita habitat is restricted to a small portion of the upper Gulf of California (also called the Sea of Cortez ), making this the smallest range of any cetacean species. They live in shallow, turbid waters of less than 150 m (490 ft) depth. Vaquitas are generalists , foraging on

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6968-726: Is hard or even impossible to test. Later biologists have tried to refine Mayr's definition with the recognition and cohesion concepts, among others. Many of the concepts are quite similar or overlap, so they are not easy to count: the biologist R. L. Mayden recorded about 24 concepts, and the philosopher of science John Wilkins counted 26. Wilkins further grouped the species concepts into seven basic kinds of concepts: (1) agamospecies for asexual organisms (2) biospecies for reproductively isolated sexual organisms (3) ecospecies based on ecological niches (4) evolutionary species based on lineage (5) genetic species based on gene pool (6) morphospecies based on form or phenotype and (7) taxonomic species,

7102-482: Is highly resistant to abrasion and degradation, hence the netting has the potential to last for many years if it is not recovered. This ghost fishing is of environmental concern. Attaching the gillnet floats with biodegradable material can reduce the problem. However it is difficult to generalize about the longevity of ghost-fishing gillnets due to the varying environments in which they are used. Some researchers have found gill-nets still catching fish and crustaceans over

7236-667: Is listed as Critically Endangered by the IUCN Red List ; the steep decline in abundance is primarily due to bycatch in gillnets from the illegal totoaba fishery. The vaquita was defined as a species by two zoologists, Kenneth S. Norris and William N. McFarland, in 1958 after studying the morphology of skull specimens found on the beach. It was not until nearly thirty years later, in 1985, that fresh specimens allowed scientists to describe their external appearance fully. The genus Phocoena comprises four species of porpoise, most of which inhabit coastal waters (the spectacled porpoise

7370-401: Is little negative impact on the environment. As soon as the gear is set the scaring takes place and the net is hauled back in. The fish are alive and discards can be returned to the sea. Encircling gillnets are commonly used by groups of small-scale fishers, and does not require other equipment. This bottom-set gear has two parts: The combined nets are maintained more or less vertically in

7504-550: Is more oceanic). The vaquita is most closely related to Burmeister's porpoise ( Phocoena spinipinnis ) and less so to the spectacled porpoise ( Phocoena dioptrica ), two species limited to the Southern Hemisphere. Their ancestors are thought to have moved north across the equator more than 2.5 million years ago during a period of cooling in the Pleistocene . Genome sequencing from an individual captured in 2017 indicates that

7638-405: Is needed, and it is low cost based on the relationship of fuel/fish. Encircling gillnets are gillnets set vertically in shallow water, with the floatline remaining at the surface so they encircle fish. Small open boats or canoes can be used to set the net around the fish. Once the fish are encircled, the fishers shout and splash the water to panic the fish so they gill or entangle themselves. There

7772-403: Is no easy way to tell whether related geographic or temporal forms belong to the same or different species. Species gaps can be verified only locally and at a point of time. One is forced to admit that Darwin's insight is correct: any local reality or integrity of species is greatly reduced over large geographic ranges and time periods. The botanist Brent Mishler argued that the species concept

7906-468: Is not valid, notably because gene flux decreases gradually rather than in discrete steps, which hampers objective delimitation of species. Indeed, complex and unstable patterns of gene flux have been observed in cichlid teleosts of the East African Great Lakes . Wilkins argued that "if we were being true to evolution and the consequent phylogenetic approach to taxa, we should replace it with

8040-518: Is set on the bottom, or at a distance above it and held in place with anchors or weights on both ends. By adjusting the design these nets can fish in surface layers, in mid water or at the bottom, targeting pelagic , demersal or benthic species. On small boats gillnets are handled by hand. Larger boats use hydraulic net haulers or net drums. Set gillnets are widely used all over the world, and are employed both in inland and sea waters. They are popular with artisanal fisheries because no specialized gear

8174-586: Is similar to Mayr's Biological Species Concept, but stresses genetic rather than reproductive isolation. In the 21st century, a genetic species could be established by comparing DNA sequences. Earlier, other methods were available, such as comparing karyotypes (sets of chromosomes ) and allozymes ( enzyme variants). An evolutionarily significant unit (ESU) or "wildlife species" is a population of organisms considered distinct for purposes of conservation. In palaeontology , with only comparative anatomy (morphology) and histology from fossils as evidence,

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8308-414: Is sometimes an important source of genetic variation. Viruses can transfer genes between species. Bacteria can exchange plasmids with bacteria of other species, including some apparently distantly related ones in different phylogenetic domains , making analysis of their relationships difficult, and weakening the concept of a bacterial species. Gillnetting Most fish have gills. A fish swims into

8442-479: Is somewhere between 3 and 6 years of age. While an initial analysis of stranded vaquitas estimated a two-year calving interval, recent sightings data suggest that vaquitas can reproduce annually. It is thought that vaquitas have a polygynous mating system in which males compete for females. This competition is evidenced by the presence of sexual dimorphism (females are larger than males), small group sizes, and large testes (accounting for nearly 3% of body mass). Because

8576-530: Is the most productive method with having highest catch per unit effort (CPUE), but has little information on the effectiveness of selectively harvesting hatchery-reared salmon. More conclusive research has been conducted jointly between the Confederated Tribes of the Colville Reservation and Bonneville Power Administration on a 10-year study on selective harvest methods of hatchery origin salmon in

8710-594: Is threatened by hybridisation, but this can be selected against once a pair of populations have incompatible alleles of the same gene, as described in the Bateson–Dobzhansky–Muller model . A different mechanism, phyletic speciation, involves one lineage gradually changing over time into a new and distinct form (a chronospecies ), without increasing the number of resultant species. Horizontal gene transfer between organisms of different species, either through hybridisation , antigenic shift , or reassortment ,

8844-629: The Edo period (1603–1868). Fisheries in the Shetland Islands, which were settled by Norsemen during the Viking Age , share cultural and technological similarities with Norwegian fisheries, including gillnet fisheries for herring. Many of the Norwegian immigrant fishermen who came to fish in the great Columbia River salmon fishery during the second half of the 19th century did so because they had experience in

8978-523: The ICZN for animals and the ICN for plants, do not make rules for defining the boundaries of the species. Research can change the boundaries, also known as circumscription, based on new evidence. Species may then need to be distinguished by the boundary definitions used, and in such cases the names may be qualified with sensu stricto ("in the narrow sense") to denote usage in the exact meaning given by an author such as

9112-466: The IUCN Red List , which is only one level above being completely extinct in the wild. It is considered the most endangered marine mammal in the world. The vaquita has been listed as critically endangered by the IUCN Red List of Threatened Species since 1996. The vaquita is at risk of extinction due to its small population size. It was approximated at one point that there were 150 individuals. In 2019,

9246-782: The UNESCO World Heritage Site where the last vaquita are located was classified as a World Heritage Site in Danger . The vaquita is also protected under the Endangered Species Act of 1973 , the Mexican Official Standard NOM-059 ( Norma Oficial Mexicana ), and Appendix I of the Convention on International Trade in Endangered Species of Wild Fauna and Flora ( CITES ). For a small population such as

9380-399: The fly agaric . Natural hybridisation presents a challenge to the concept of a reproductively isolated species, as fertile hybrids permit gene flow between two populations. For example, the carrion crow Corvus corone and the hooded crow Corvus cornix appear and are classified as separate species, yet they can hybridise where their geographical ranges overlap. A ring species is

9514-498: The jaguar ( Panthera onca ) of Latin America or the leopard ( Panthera pardus ) of Africa and Asia. In contrast, the scientific names of species are chosen to be unique and universal (except for some inter-code homonyms ); they are in two parts used together : the genus as in Puma , and the specific epithet as in concolor . A species is given a taxonomic name when a type specimen

9648-406: The "cynical species concept", and arguing that far from being cynical, it usefully leads to an empirical taxonomy for any given group, based on taxonomists' experience. Other biologists have gone further and argued that we should abandon species entirely, and refer to the "Least Inclusive Taxonomic Units" (LITUs), a view that would be coherent with current evolutionary theory. The species concept

9782-626: The Mexican Navy to detect fishing in the Refuge Area and remove illegal gillnets. In March 2020, the U.S. National Marine Fisheries Service (NMFS) announced a ban on imported Mexican shrimp and other seafood caught in vaquita habitat in the northern Gulf of California. In response to the dire circumstances facing the vaquita as by-catch of the illegal totoaba trade, in 2017 Earth League International (ELI) commenced an investigation and intelligence gathering operation called Operation Fake Gold, during which

9916-622: The Origin of Species explained how species could arise by natural selection . That understanding was greatly extended in the 20th century through genetics and population ecology . Genetic variability arises from mutations and recombination , while organisms themselves are mobile, leading to geographical isolation and genetic drift with varying selection pressures . Genes can sometimes be exchanged between species by horizontal gene transfer ; new species can arise rapidly through hybridisation and polyploidy ; and species may become extinct for

10050-544: The Recovery of the Vaquita (CIRVA) recommended that some vaquitas be removed from the high-density fishing area and be relocated to protected sea pens. This effort, called VaquitaCPR, captured two vaquitas in 2017; one was later released and the other died shortly after capture after both suffered from shock. Local and international conservation groups, including Museo de Ballena and Sea Shepherd Conservation Society , are working with

10184-458: The Sri Lankan gillnet fishery, one dolphin is caught for every 1.7–4.0 tonnes of tuna landed . This compares poorly with the rate of one dolphin per 70 tonnes of tuna landed in the eastern Pacific purse seine tuna fishery. Many types of gillnets are used by fisheries scientists to monitor fish populations. Vertical gillnets are designed to allow scientists to determine the depth distribution of

10318-467: The Upper Columbia River by purse seine and tangle net. Their 2009 and 2010 findings show that purse seines have a higher percentage of survivability and higher CPUE than does tangle nets. A Colville Tribe biologist reports that during these two years the tribe harvested 3,163 hatchery Chinook while releasing 2,346 wild Chinook with only 1.4% direct or immediate mortality using purse seines, whereas

10452-405: The abbreviation "sp." in the singular or "spp." (standing for species pluralis , Latin for "multiple species") in the plural in place of the specific name or epithet (e.g. Canis sp.). This commonly occurs when authors are confident that some individuals belong to a particular genus but are not sure to which exact species they belong, as is common in paleontology . Authors may also use "spp." as

10586-570: The amount of hybridisation is insufficient to completely mix their respective gene pools . A further development of the recognition concept is provided by the biosemiotic concept of species. In microbiology , genes can move freely even between distantly related bacteria, possibly extending to the whole bacterial domain. As a rule of thumb, microbiologists have assumed that members of Bacteria or Archaea with 16S ribosomal RNA gene sequences more similar than 97% to each other need to be checked by DNA–DNA hybridisation to decide if they belong to

10720-427: The ancestral vaquitas had already gone through a major population bottleneck in the past, which may explain why the few remaining individuals are still healthy despite the very low population size. "Vaquita" is Spanish for "little cow". The smallest living species of cetacean, the vaquita can be easily distinguished from any other species in its range. It has a small body with an unusually tall triangular dorsal fin,

10854-792: The average fisherman, thus making their range and mobility increasingly larger. It also served to make the industry much more competitive, as the fisherman were forced to invest more in boats and equipment to stay current with developing technology. The introduction of fine synthetic fibres such as nylon in the construction of fishing gear during the 1960s marked an expansion in the commercial use of gillnets. The new materials were cheaper and easier to handle, lasted longer and required less maintenance than natural fibres. In addition, multifilament nylon , monofilament or multimonofilament fibres become almost invisible in water, so nets made with synthetic twines generally caught greater numbers of fish than natural fibre nets used in comparable situations. Nylon

10988-630: The banning of gillnet fishing through letters to federal fishing companies. The progress for these regulations have been paused in California mid 2017. According to the High Seas Fishing Compliance Act from 1996, a permit is require for all commercial fishing vessels that are registered in the United States and under this act, vessels must have a record of all their fishing efforts on the high seas. As of November 2017, there has been

11122-471: The beginning of the 1900s, steam powered ships would haul these smaller boats to their fishing grounds and retrieve them at the end of each day. However, at that time gas powered boats were beginning to make their appearance, and by the 1930s, the row-sail boat had virtually disappeared, except in Bristol Bay, Alaska, where motors were prohibited in the gillnet fishery by territorial law until 1951. In 1931,

11256-474: The biological species concept, "the several versions" of the phylogenetic species concept, and the idea that species are of the same kind as higher taxa are not suitable for biodiversity studies (with the intention of estimating the number of species accurately). They further suggested that the concept works for both asexual and sexually-reproducing species. A version of the concept is Kevin de Queiroz 's "General Lineage Concept of Species". An ecological species

11390-505: The biological species concept, a cladistic species does not rely on reproductive isolation – its criteria are independent of processes that are integral in other concepts. Therefore, it applies to asexual lineages. However, it does not always provide clear cut and intuitively satisfying boundaries between taxa, and may require multiple sources of evidence, such as more than one polymorphic locus, to give plausible results. An evolutionary species, suggested by George Gaylord Simpson in 1951,

11524-402: The black market by cartels for profit. The Mexican government, international committees, scientists, and conservation groups have recommended and implemented plans to help reduce the rate of bycatch, enforce gillnet bans, and promote population recovery. Protection efforts throughout Mexico have taken place in order to preserve the population. In 2017, the Government of Mexico established it as

11658-428: The boundaries between closely related species become unclear with hybridisation , in a species complex of hundreds of similar microspecies , and in a ring species . Also, among organisms that reproduce only asexually , the concept of a reproductive species breaks down, and each clone is potentially a microspecies. Although none of these are entirely satisfactory definitions, and while the concept of species may not be

11792-399: The captured fish. United Nations General Assembly Resolution 46/215 called for the cessation of all "large-scale pelagic drift-net fishing" in international waters by the end of 1992. The laws of individual countries vary with regard to fishing in waters under their jurisdiction. Possession of gillnets is illegal in some U.S. states and heavily regulated in others. Oregon voters had

11926-687: The chance to decide on whether gillnetting will continue in the Columbia River in November 2012 by voting on Measure 81. The measure was defeated with 65% of Oregon voters voting against the measure and allowing commercial gillnet fishing to continue on the Columbia River. The Columbia River Basin is currently under a management agreement that spans from 2008 to December 31, 2017. This management agreement looks to gather information on fish harvesting through means including gillnets. The parties involved will convene again to decide on further action after

12060-433: The concept of a chronospecies can be applied. During anagenesis (evolution, not necessarily involving branching), some palaeontologists seek to identify a sequence of species, each one derived from the phyletically extinct one before through continuous, slow and more or less uniform change. In such a time sequence, some palaeontologists assess how much change is required for a morphologically distinct form to be considered

12194-416: The concept of the chronospecies since fossil reproduction cannot be examined. The most recent rigorous estimate for the total number of species of eukaryotes is between 8 and 8.7 million. About 14% of these had been described by 2011. All species (except viruses ) are given a two-part name , called a "binomial". The first part of a binomial is the genus to which the species belongs. The second part

12328-814: The current agreement ends. The gill-netting season in Minnesota can vary from county to county and the net types used are regulated on a lake by lake basis by the Minnesota Department of Natural Resources. Virginia's gill-netting season is regulated by the Virginia Marine Resources Commission. During different months of the year, certain rivers have restricted mesh sizes, which vary by location. There have been proposed regulations to shut down drift gillnet fisheries whose by-catch numbers (which include dolphins, sea turtles and other marine life) were too high. In 2014, California lawmakers pushed for

12462-477: The end of June 2024. There are some concerns that the hooks will create ghost nets , and the navy and Sea Shepherd have removed nets trapped on hooks after being caught. Given their proximity to the coast, vaquitas are exposed to habitat alteration and pollution from runoff. Pesticides present in the water as a result of runoff from agriculture are a threat as they can be ingested by the vaquitas, causing harm and even death. Exposure to toxic compounds has also had

12596-464: The entire illicit totoaba maw (swim bladder) international supply chain, from Mexico to China, has been mapped and researched. Thanks to the confidential data that ELI shared with the Mexican authorities, in November 2020, a series of important arrests were made in Mexico. To date, efforts have been unsuccessful in solving the complex socioeconomic and environmental issues that affect vaquita conservation and

12730-610: The estimated 400,000 annual avian by-catch in coastal fisheries. These include three strategies that have a possible reduction in up to 75% of avian by-catch: gear modifications, where visual devices will be placed near the top of the net so birds will be able to see the nets; abundance-based fishery openings, where of birds will determine whether the nets will be set out or not; and time-of-day restrictions, which goes along with abundance- where bird by catch tended to occur at dawn and dusk, where as fish catch occurred mostly at dawn. For marine mammal by-catch, field experiments have shown that

12864-435: The evidence to support hypotheses about evolutionarily divergent lineages that have maintained their hereditary integrity through time and space. Molecular markers may be used to determine diagnostic genetic differences in the nuclear or mitochondrial DNA of various species. For example, in a study done on fungi , studying the nucleotide characters using cladistic species produced the most accurate results in recognising

12998-603: The first powered drum was created by Laurie Jarelainen. The drum is a circular device that is set to the side of the boat and draws in the nets. The powered drum allowed the nets to be drawn in much faster and along with the faster gas powered boats, fisherman were able to fish in areas they had previously been unable to go into, thereby revolutionizing the fishing industry. During World War II, navigation and communication devices, as well as many other forms of maritime equipment (ex. depth-sounding and radar) were improved and made more compact. These devices became much more accessible to

13132-413: The future due to a bottleneck of genetic diversity within the reduced population. The reduced gene pool lowers the rate of adaptation and increases the rate of inbreeding , potentially leading to inbreeding depression . This phenomenon is attributed to the anthropogenic Allee effect , specifically on the end where small population size leads to low species fitness because of a lack of genetic diversity and

13266-478: The gillnet fishery for cod in the waters surrounding the Lofoten Islands of northern Norway . Gillnets were used as part of the seasonal round by Swedish fishermen as well. Welsh and English fishermen gillnetted for Atlantic salmon in the rivers of Wales and England in coracles , using hand-made nets, for at least several centuries. These are but a few of the examples of historic gillnet fisheries around

13400-401: The gillnets is very effective at selecting or regulating the size of fish caught. The drift net has a low fuel/fish energy consumption compared to other fishing gear. However, the issue of concern with this type of net is the bycatch of species that are not targeted, such as marine mammals, seabirds and to a minor extent turtles. The use of drift nets longer than 2.5 kilometres on the high seas

13534-501: The greater Gulf of California ecosystem. Necessary action includes habitat protection, resource management, education, fisheries enforcement, alternative livelihoods for fishermen, and raising awareness of the vaquita and associated issues. Jaramillo-Legorreta, et al. stated in 2007 that captive breeding programs were not a viable option for saving the species from extinction. The Secretariat of Environment and Natural Resources (SEMARNAT) announced on February 27, 2021, that it may reduce

13668-401: The mark-selective fishery for spring Chinook salmon on the lower Columbia River have a standard mesh size of 4 + 1 ⁄ 4 inches (11 cm). Short net lengths and soak times are used in an effort to land fish in good condition. Tangle nets are typically used in situations where the release of certain (usually wild) fish unharmed is desirable. In a typical situation calling for the use of

13802-794: The meshes as far as their gills are not retained. This gives gillnets the ability to target a specific size of fish, unlike other net gears such as trawls , in which smaller fish pass through the meshes and all larger fish are captured in the net . Commercial gillnet fisheries are still an important method of harvesting salmon in Alaska, British Columbia, Washington, and Oregon. In the lower Columbia River , non-Indian commercial salmon fisheries for spring Chinook have developed methods of selectively harvesting adipose fin clipped hatchery salmon using small mesh gillnets known as tangle nets or tooth nets. Non-adipose fin clipped fish (primarily natural origin salmon) must be released. Fishery management agencies estimate

13936-493: The northern end of the Gulf of California, which has a high aquatic mammal bycatch rate, is consumed in the United States. As such, U.S. consumers of this shrimp are likely contributing to the vaquita extinction crisis. The Marine Mammal Protection Act of 1972, which forbids foreign fishers from exporting seafood with high levels of marine mammal bycatch, may allow for better efforts to preserve endangered vaquitas. To learn more about

14070-419: The number of vaquitas dying off. Anthropogenic effects of a rise in commercial fishing such as accidental bycatch, illegal fishing, and entanglement have been linked to the cause of their decline. Shrimp fishing and gillnets create entanglement issues for the vaquita. Aspects of illegal fishing include open access fisheries and absent fisheries management has correlated towards poaching of the main prey source of

14204-478: The numerous fungi species of all the concepts studied. Versions of the phylogenetic species concept that emphasise monophyly or diagnosability may lead to splitting of existing species, for example in Bovidae , by recognising old subspecies as species, despite the fact that there are no reproductive barriers, and populations may intergrade morphologically. Others have called this approach taxonomic inflation , diluting

14338-408: The operating vessel, the driftnetter or drifter . Drift nets are usually used to catch schooling forage fish such as herring and sardines , and also larger pelagic fish such as tuna , salmon and pelagic squid . Net haulers are usually used to set and haul driftnets, with a drifter capstan on the forepart of the vessel. In developing countries most nets are hauled by hand. The mesh size of

14472-585: The paper is accepted for publication. The type material is usually held in a permanent repository, often the research collection of a major museum or university, that allows independent verification and the means to compare specimens. Describers of new species are asked to choose names that, in the words of the International Code of Zoological Nomenclature , are "appropriate, compact, euphonious, memorable, and do not cause offence". Books and articles sometimes intentionally do not identify species fully, using

14606-674: The person who named the species, while the antonym sensu lato ("in the broad sense") denotes a wider usage, for instance including other subspecies. Other abbreviations such as "auct." ("author"), and qualifiers such as "non" ("not") may be used to further clarify the sense in which the specified authors delineated or described the species. Species are subject to change, whether by evolving into new species, exchanging genes with other species, merging with other species or by becoming extinct. The evolutionary process by which biological populations of sexually-reproducing organisms evolve to become distinct or reproductively isolated as species

14740-473: The population had stabilized since it had last been recorded in 2021. In October 2024, Colossal Biosciences announced their non-profit foundation dedicated to conservation of extant species, with one of their first projects being the vaquita. Colossal plans to biobank genetic material to revive the species if it were to become extinct, and to use acoustic sensors and drones to monitor vaquitas in collaboration with CONANP . Roughly 80% of shrimp caught in

14874-428: The potential for inbreeding. Because of their small population size, vaquitas are experiencing a negative Allee effect, attributing to even smaller population growth rates, driving them further into extinction. However, a 2022 study on the genetic diversity of the vaquita suggests that the marine mammal’s historically small population ensures it is unlikely to greatly suffer from inbreeding depression. Attempts to start

15008-421: The predation of sharks towards vaquita do result in a decline in population and is seen as an alternate threat, northern fishing fleets also negatively impact this small marine mammal because the negative influence of incidental catch is greater than the positive influence of predation reduction by shark fisheries. Populations that experience a sudden decline in numbers are often more vulnerable to other threats in

15142-470: The progress made with legal fishermen, hundreds of poachers continued to fish in the exclusion zone. Poaching continues as the swim bladders of totoaba can sell for anywhere from $ 20,000 to upwards of $ 80,000, and they are often referred to as the "cocaine of the sea." A black market for totoaba swim bladders has developed fairly recently in China (including Hong Kong). In 2017, poachers received up to US$ 20,000 for

15276-448: The protected area for the vaquita in the Sea of Cortés as there are only ten of the porpoises left and it may never recuperate its historical range. Beginning in July 2022, the Mexican government placed 193 concrete blocks in the Gulf of California no-tolerance zone, intended to allow the detection of nets by acoustic sonar and prevent further entrapment of vaquitas. Creating protected areas

15410-487: The result of misclassification leading to questions on whether there really are any ring species. The commonly used names for kinds of organisms are often ambiguous: "cat" could mean the domestic cat, Felis catus , or the cat family, Felidae . Another problem with common names is that they often vary from place to place, so that puma, cougar, catamount, panther, painter and mountain lion all mean Puma concolor in various parts of America, while "panther" may also mean

15544-573: The ring. Ring species thus present a difficulty for any species concept that relies on reproductive isolation. However, ring species are at best rare. Proposed examples include the herring gull – lesser black-backed gull complex around the North pole, the Ensatina eschscholtzii group of 19 populations of salamanders in America, and the greenish warbler in Asia, but many so-called ring species have turned out to be

15678-508: The same species. This concept was narrowed in 2006 to a similarity of 98.7%. The average nucleotide identity (ANI) method quantifies genetic distance between entire genomes , using regions of about 10,000 base pairs . With enough data from genomes of one genus, algorithms can be used to categorize species, as for Pseudomonas avellanae in 2013, and for all sequenced bacteria and archaea since 2020. Observed ANI values among sequences appear to have an "ANI gap" at 85–95%, suggesting that

15812-529: The same species. When two species names are discovered to apply to the same species, the older species name is given priority and usually retained, and the newer name considered as a junior synonym, a process called synonymy . Dividing a taxon into multiple, often new, taxa is called splitting . Taxonomists are often referred to as "lumpers" or "splitters" by their colleagues, depending on their personal approach to recognising differences or commonalities between organisms. The circumscription of taxa, considered

15946-413: The selectivity of commercial gillnet harvests. The study found that the larger females (>550 mm) of all age classes were most susceptible to harvest. The study suggests that smaller, younger fish were more likely to successfully traverse the gillnet fishery and reproduce than the larger fish. The study also found that the average length of sockeye harvested from 1946 to 2005 was 8 mm larger than

16080-535: The sockeye who escaped the gillnet fishery to spawn, reducing the fecundity of the average female by 5%, or 104 eggs. If a salmon enters a gillnet, but manages to escape, it can sustain injuries. These injuries can lead to a lower degree of reproductive success. A study aimed at quantifying mortality of Bristol Bay sockeye salmon due to gillnet-related injuries found that 11–29% of sockeye sustained fishery-related injuries attributable to gillnets, and 51% of those fish were expected to not reproduce. Gillnets are sometimes

16214-502: The species concept and making taxonomy unstable. Yet others defend this approach, considering "taxonomic inflation" pejorative and labelling the opposing view as "taxonomic conservatism"; claiming it is politically expedient to split species and recognise smaller populations at the species level, because this means they can more easily be included as endangered in the IUCN red list and can attract conservation legislation and funding. Unlike

16348-496: The tangle net was far less productive but had an approximate 12.5% mortality. Researchers commented that the use of recovery boxes and shortened periods between checking the nets would have likely decreased mortality rates. While there is data that shows success of selective methods of harvest at protecting wild and ESA listed salmon, there still must be social acceptance of new methods of fishing. There have also been studies done to see if differing strategies could potentially decrease

16482-639: The top, to use as floats. This allowed the net to suspend straight up and down in the water. Each net would be suspended either from shore or between two boats. Native fishers in the Pacific Northwest, Canada, and Alaska still commonly use gillnets in their fisheries for salmon and steelhead . Both drift gillnets and setnets have long been used by cultures around the world. There is evidence of fisheries exploitation, including gillnetting, going far back in Japanese history, with many specific details available from

16616-512: The use of gillnets in these fisheries. Gillnets are also used out in the deep sea for fisheries whose primary catch is swordfish. California driftnet fisheries have some of the highest rates of by-catch with 12 percent of the catch being the targeted swordfish while up to 68 percent of the catch being by-catch that will be tossed back to sea. Given the selective properties of gillnet fishing, alternative methods of harvest are currently being studied. Recent WDF&W reports suggest that purse seine

16750-436: The use of pingers on nets resulted in significantly lower numbers of by-catch than nets without pingers. After this study was completed by Jay Barlow, it was determined that there would be a 12-fold decrease in short-beaked common dolphins caught, a 4-fold decrease in other cetaceans and a 3-fold decrease in pinnipeds for nets containing pingers. The FAO classifies gillnet gear types as follows: Set gillnets consist of

16884-406: The usual way by floats on the floatline and weights on the groundline. They are set on the bottom. After a time depending on the target species, they are hauled on board. Traditional combined nets were hauled by hand, especially on smaller boats. Recent hydraulic driven net haulers are now common. The gilled, entangled and enmeshed fish are removed from the net by hand. Of some concern with this method

17018-548: The vaquita and conservation efforts, visit: Species A species ( pl. : species) is a population of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring , typically by sexual reproduction . It is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity . Other ways of defining species include their karyotype , DNA sequence, morphology , behaviour, or ecological niche . In addition, paleontologists use

17152-424: The vaquita to recover after a severe decline in population size is very difficult. This conservation status is strongly influenced in part of the species reproductive biology. The large amount of unknown surrounding the key reproductive parameters of the vaquita makes understanding its potential for recovery even harder. The vaquita is found only in the upper Gulf of California, Mexico area. Anthropogenic effects of

17286-437: The vaquita was only fully described in the late 1980s, historical abundance is unknown. Since 1983, all confirmed specimens, records, and sightings of P. sinus were evaluated. There were 45 records of P. sinus that were collected by skeletal remains, photographs, and sightings in 1983. The first comprehensive vaquita survey throughout their range took place in 1997 and estimated a population of 567 individuals. By 2007 abundance

17420-442: The vaquita. The drastic decline in vaquita abundance is the result of fisheries bycatch in commercial and illegal gillnets , including fisheries targeting the now-vulnerable Totoaba , shrimp , and other available fish species. Despite government regulations, including a partial gillnet ban in 2015 and establishment of a permanent gillnet exclusion zone in 2017, illegal totoaba fishing remains prevalent in vaquita habitat, and as

17554-537: The wild. It is difficult to define a species in a way that applies to all organisms. The debate about species concepts is called the species problem. The problem was recognised even in 1859, when Darwin wrote in On the Origin of Species : I was much struck how entirely vague and arbitrary is the distinction between species and varieties. He went on to write: No one definition has satisfied all naturalists; yet every naturalist knows vaguely what he means when he speaks of

17688-572: The world. Gillnetting was an early fishing technology in colonial America, used for example, in fisheries for Atlantic salmon and shad. Immigrant fishermen from northern Europe and the Mediterranean brought a number of different adaptations of the technology from their respective homelands with them to the rapidly expanding salmon fisheries of the Columbia River from the 1860s onward. The boats used by these fisherman were typically around 25 feet (8 m) long and powered by oars. Many of these boats also had small sails and were called "row-sail" boats. At

17822-625: Was banned by the United Nations in 1991. Prior to this ban, drift nets were reaching lengths of 60 kilometres. However, there are still serious concerns with ongoing violations. The tangle net, or tooth net, originated in British Columbia, Canada, as a gear specifically developed for selective fisheries. Tangle nets have smaller mesh sizes than standard gillnets. They are designed to catch fish by their nose or jaw, enabling bycatch to be resuscitated and released unharmed. Tangle nets as adapted to

17956-415: Was estimated to have dropped to 150. Population abundance as of 2018 was estimated at less than 19 individuals. Given the continued rate of bycatch and low reproductive output from a small population, it is estimated that there are fewer than 10 vaquitas alive as of February 2022. In 2023, it is still estimated that there are as few as 10 in the wild. A 2024 survey observed a minimum of 6 to 8 individuals (with

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