Literaturdatenbank
Literaturdatenbank |
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Roosenburg, W. M. , The history of commercial exploitation of the diamondback terrapin (malaclemys terrapin) provides lessons for turtle conservation. Unpublished paper presented at USFWS Workshop on Conservation and Trade Management of Freshwater and Terrestrial Turtles in the United States.
Added by: Sarina Wunderlich (06 Jul 2014 16:17:17 UTC) |
| Resource type: Conference Paper BibTeX citation key: anon2010.16441 View all bibliographic details  |
Categories: General Keywords: Habitat - habitat, Lissemys punctata, Nordamerika - North America, Schildkröten - turtles + tortoises, Trionychidae Creators: Roosenburg Collection: USFWS Workshop on Conservation and Trade Management of Freshwater and Terrestrial Turtles in the United States |
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| Abstract |
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The diamondback terrapin (Malaclemys terrapin) has a long and rich history of commercial exploitation and, as a consequence, has become an iconic species for turtle conservation. The historical records of exploitation in Chesapeake Bay and the current studies of terrapin populations illustrate the susceptibility of turtle populations to over-harvesting, particularly the removal of juveniles and adults. More generally, diamondback terrapins have delayed maturity, low reproductive rates, and high adult survival: life history traits shared by almost all turtles that make them bad candidates for unregulated commercial harvest. Thus, the patterns of exploitation and decline demonstated in terrapins can inform the conservation of all turtles subject to commercial harvest. Terrapins were first recognized as food source and a new world resource with the potential for exploitation in 1588. By the mid 1800's the demand for terrapin flesh generated lucrative prices that drove a thriving fishery that depleted stocks throughout Chesapeake Bay and the entire species range. A peak in terrapin harvest in 1891 of almost 90,000 lbs led to a significant population decline; by 1920 only 823 lbs were harvested in Chesapeake Bay. The terrapin fishery waned until the late 1940's when a number of record harvest years reported takes in excess of 200,000 lbs / year. By the mid 1950's terrapin harvests declined again to less than 10,000 lbs / year and continued to dwindled to a minimal take in the 1980's - 90's. Beginning in 2002, terrapin harvest began to increase, correlated with an increasing demand for turtle flesh from Asian markets. The increase in harvest during the last decade contributed to the closure through legislative action of the commercial fishery. The closure of Maryland's terrapin fishery was not regulated by the state management agency, MD- Department of Natural Resources. A grass-roots effort coordinated by a group of citizens and scientists began the legislative process that ultimately resulted in a statute that prohibits the commercial harvest of terrapins. Necessary, but not sufficient for this process was data illustrating that terrapin harvest is unsustainable, local populations had declined, and new threats (habitat loss and by-catch mortality) were reducing recruitment, juvenile, and adult survivorship. Though the historical and contemporary data could justify ending commercial exploitation, political forces made the regulatory change difficult. In the end, education, petitions, minimal economic impact, and political pressure played a much greater role in closing the fishery than the science. Despite the end of commercial exploitation, terrapin populations in Chesapeake Bay are still struggling as habitat loss and mortality as by-catch in other commercial fisheries continues. In particular, the mortality in the commercial blue crab (crab pot) fishery reduces juvenile survivorship; populations continue to decline despite efforts to increase recruitment through nest protection and head-start programs. Furthermore, a lack of education and enforcement of existing regulations implemented to protect terrapins contribute to a persistent decline. Although the closure of the commercial harvest was an important first step for terrapin conservation, it has not instantly put the terrapin on the path to recovery as new threats negate the impact of fishery closure. What can we learn from the terrapin fishery in Chesapeake Bay? The twice occurring peak and collapse of the terrapin harvest during the past 150 years demonstrate the predicted rapid decline/collapse caused by commercial exploitation and the subsequent long-term recovery of turtle populations. The modern environmental context for terrapins and all turtles has deteriorated relative to the environment that allowed for the recovery of terrapins; new threats that increase juvenile and adult mortality (roads and by-catch), habitat loss and fragmentation, and pollution will stall or prevent recovery. Similar threats affect nearly all turtle populations in the United States. Education programs are critical to teach the public of the sensitivity of turtle populations, but also to expose the harvest to supply Asian markets. The general public is surprised and eager to help when they learn that turtles are commercially exploited to be shipped overseas. This public interest and concern for turtles can exert sufficient political pressure to outweigh the minimal economic gain of harvesting turtles. Finally, the elimination of the commercial exploitation of all turtles is only the start of a long-term conservation initiative that should address any and all factors that decrease juvenile and adult survivorship.
Added by: Sarina Wunderlich |