The Impact of Commercial Exploitation on Sawfish and Shark Populations in Lake Nicaragua

Thorson, Thomas B.

doi:10.1577/1548-8446(1982)007<0002:tioceo>2.0.co;2

Cited by 67 publications

(46 citation statements)

References 3 publications

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“…Distribution and aspects of the biology of elasmobranchs from fresh and/or estuarine waters of the Indian River lagoon system of Florida and in North Carolina have also been studied (Snelson & Williams, 1981;Schwartz, 1995). However, with the exception of e¡ects of commercial ¢shing and dam building on neotropical populations of C. leucas and P. perotetti (Thorson, 1976b(Thorson, , 1982cMontoya & Thorson, 1982), status and conservation of freshwater and euryhaline elasmobranchs have been largely ignored until a decade ago (Compagno, 2002).…”

Section: Introductionmentioning

confidence: 99%

conservation of freshwater and euryhaline elasmobranchs: a review

Martin¹

2005

J. Mar. Biol. Ass.

117

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Published data on the diversity, life history, ecology, and status of freshwater and euryhaline elasmobranchs was reviewed in the context of anthropogenic threats and principles of conservation biology. At least 171 species of elasmobranch, representing 68 genera and 34 families, are recorded from fresh or estuarine waters. Of these, over half are marginal in estuaries, less than one-tenth are euryhaline, and one-¢fth are obligate in fresh water. Obligate freshwater elasmobranchs are dominated by myliobatoid stingrays, of which two-thirds are potamotrygonids endemic to Atlantic drainages of South America. Freshwater and euryhaline elasmobranchs adhere to strongly K-selected life histories and feed at high trophic levels, similar to those of their marine relatives. However, freshwater and euryhaline elasmobranchs are also subject to habitat constraints, notably more limited volume and physicochemical variability than the ocean, that may render them more vulnerable than marine elasmobranchs to the e¡ects of human activities. The greatest diversity and abundance of freshwater and euryhaline elasmobranchs occur in tropical countries with enormous and rapidly increasing human populations, notably South America, West Africa, and south-east Asia. Knowledge of the biology, distribution, ecology, and status of freshwater and euryhaline elasmobranchs is frustrated by unresolved taxonomic problems, which are brie£y summarized. To clarify selected issues in the conservation of freshwater and euryhaline elasmobranchs, special attention is given to sharks of the genus Glyphis, pristids, and potamotrygonids. To foster live release when possible as well as prevent discard of specimens and loss of data, an illustrated key to di¡erentiate Carcharhinus from Glyphis sharks is provided. Obligate freshwater elasmobranchs with limited geographic ranges are deemed most vulnerable to extinction, but euryhaline elasmobranchs that require access to the sea to breed are also at signi¢cant risk. Based on the foregoing data and principles of conservation biology, suggested action plans for the conservation of freshwater and euryhaline elasmobranchs and the conservation of freshwater habitats are provided.

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Section: Introductionmentioning

confidence: 99%

conservation of freshwater and euryhaline elasmobranchs: a review

Martin¹

2005

J. Mar. Biol. Ass.

117

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“…However, the majority of shark fishing takes place in Pacific waters: refer to the Northeast Pacific regional report for additional information. Lake Nicaragua elasmobranchs were documented as overfished as early as 1982 (Thorson 1982a). Of particular concern is the marked decline of sawfishes, which were formerly abundant in the lake and adjacent rivers.…”

Section: Nicaragua (Atlantic Coast)mentioning

confidence: 99%

“…Life history data for sawfishes are largely lacking. Thorson's (1976Thorson's ( , 1982aThorson's ( , 1982b) studies of P. perotteti in Lake Nicaragua are the major data sources on the species, with limited peripheral or anecdotal information available elsewhere (e.g. Bigelow and Schroeder 1953;Thorson et al 1966).…”

Section: Sawfishmentioning

confidence: 99%

“…In most areas where sawfish occur around the world, their population sizes have been reduced to very low levels by fishing (e.g. Thorson 1982a). CharvetAlmeida (2002) reports that Pristis perotteti and P. pectinata are routinely captured and their meat, fins and rostra (worth up to US$300 depending on size) are sold in Belém, northern Brazil.…”

Section: Batoid Fisheriesmentioning

confidence: 99%

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Sharks, rays and chimaeras: the status of the chondrichthyan fishes

Burgess¹,

Cailliet²,

Camhi³

et al. 2005

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“…These are large to massive (3.2 to 7 m maximum total length, TL) and highly recognisable shark-like batoids that were previously common to abundant in soft-bottom habitats of shallow, warm waters worldwide, often enjoying close associations with human culture through mythology and folklore (Harrison & Dulvy 2014). Despite these factors, research on sawfishes was conspicuously lacking, and one of the first focused field studies was also that which documented their disastrous fisheries-driven extinction in Lake Nicaragua (Thorson 1982). Even with this clear example of vulnerability and a significant growth in elasmobranch research in ensuing decades, catastrophic global de clines went almost unnoticed, with a notable exception in the grey literature: 'The Shark Specialist Group is becoming increasingly concerned about widespread reports...of an apparent serious decline over the past few decades of formerly healthy populations of all species of sawfish' (Anonymous 1996).…”

Section: Introductionmentioning

confidence: 99%

Are guitarfishes the next sawfishes? Extinction risk and an urgent call for conservation action

Moore¹

2017

Endang. Species. Res.

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Focusing on the most critical conservation priorities to prevent extinctions risks missing declines of lower priority taxa that may become tomorrow's emergency. Sawfishes (5 species) underwent catastrophic but largely unnoticed global declines in the latter part of the 20th century, and are now the subject of intensive research and conservation efforts. Guitarfishes (at least 55 species) share many characteristics with sawfishes: they are shark-like batoids with an often large body, prefer sedimentary habitats in warm shallow coastal waters exposed to intensive fisheries, and have high value fins and good quality meat. Guitarfishes represent a unique element of evolution and biodiversity and are vital components of complex coastal socio-ecological systems. Existing global IUCN Red List of Threatened Species assessments for nearly 60% of guitarfish species are 10 or more years old, and over 70% of species are either in threatened categories or Data Deficient. Recently described taxa not yet assessed include those likely to be at risk of extinction. Severe declines and localised extinctions have already been reported for guitarfishes. In notable contrast to sawfishes, total extinction of several guitarfish species is plausible given small distributions occurring solely in developing or least developed countries where conservation is highly challenging. Furthermore, species identification of guitarfishes is often problematic and they may lack the appeal often needed to promote conservation. To ensure that they do not follow the same trajectory as sawfishes, there is an urgent need for comprehensive and coordinated action on guitarfishes, which in many cases could integrate with sawfish conservation efforts.

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The Impact of Commercial Exploitation on Sawfish and Shark Populations in Lake Nicaragua

Cited by 67 publications

References 3 publications

conservation of freshwater and euryhaline elasmobranchs: a review

conservation of freshwater and euryhaline elasmobranchs: a review

Sharks, rays and chimaeras: the status of the chondrichthyan fishes

Are guitarfishes the next sawfishes? Extinction risk and an urgent call for conservation action

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