Literaturdatenbank
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Smeenk, N. A. (2010). The population ecology of a headstart supplemented population of diamondback terrapins (malaclemys terrapin) at the poplar island environmental restoration project in the middle chesapeake bay. Unpublished thesis Master of Science (MS), Ohio University.
Added by: Sarina Wunderlich (12 Dec 2010 20:43:14 UTC) |
| Resource type: Thesis/Dissertation BibTeX citation key: Smeenk2010 View all bibliographic details  |
Categories: General Keywords: Emydidae, Habitat = habitat, Malaclemys, Malaclemys terrapin, Nordamerika = North America, Schildkröten = turtles + tortoises Creators: Smeenk Publisher: Ohio University |
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| Abstract |
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The efficacy of headstarting programs to supplement populations of long-lived, late-maturing organisms is unknown. Despite this fact, headstarting programs have been criticized for not addressing or mitigating the actual causes for population declines. Over the last five years, 642 diamondback terrapin (Malaclemys terrapin) hatchlings were headstarted and released at the Poplar Island Environmental Restoration Project (PIERP) in the Chesapeake Bay. I conducted a mark-recapture study to determine the effectiveness of headstarting in this population. I trapped terrapins using fyke nets and tall crab pots. Captured terrapins were tagged and I recorded morphometrics, mass, sex, and age. I compared the PIERP population to a 23 year mark-recapture study in the Patuxent River (PR) of a non-headstart supplemented population where data were collected in the same manner and commercial crab fishing does not occur. The sex ratio of the PIERP population was highly female biased (9:1). There was no difference in size or age distributions among the two populations, with both skewed toward larger and older individuals. I estimated the population size at PIERP to be 204-406 individuals and a stage-structured Leftkovich matrix population model indicated that the PIERP is declining (?=0.940). The low population growth rate and similarities between the PIERP and PR populations suggest that headstarting is not increasing hatchling and juvenile survival. I suggest that the lack of juvenile and male turtles in the PIERP population and ineffectiveness of headstarting are caused by differential mortality of these groups due to bycatch in crab pots and support the conclusion that headstarting is a "halfway technology" that does not address the initial causes for population declines. I recommend that headstarting not be considered a viable management strategy until mortality caused by crab pot bycatch is resolved through the use of bycatch reduction devices and spatial restrictions on commercial crab pots.
Added by: Sarina Wunderlich |