Assessment of Sea-Turtle Status and Trends Integrating Demography and Abundance (2010) / Chapter Skim
Currently Skimming:
1 Introduction
1 Introduction
Pages 11-28
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, and leatherback (Dermochelys coriacea) -- are listed as endangered or threatened under the Endangered Species Act, thereby prohibiting their direct harvest.
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There have been recommendations for improved data collection and analysis for status determination and assessment modeling in nearly every report and status review document published by the two federal agencies responsible for seaturtle management -- the National Marine Fisheries Service (NMFS)
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Trends based on numbers of nests or nest ing females. Data from National Marine Fisheries Service and U.S.
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; LDM Atlantic Southeast Fisheries Science Center
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Obtain key vital rates, increasing; northern setting strandings especially survival and life subpopulation recovery limits was completely stage duration. goals unlikely to be satisfactory to all Group 2.
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ASSESSMENT OF SEA-TURTLE STATUS AND TRENDS TABLE 1.2 Continued Geographic Document Species Area Reference Year Methods Leatherback Western National Marine 2001 Trend analysis North Fisheries Service (nests) Atlantic Southeast Fisheries Science Center Leatherback Atlantic Turtle Expert 2007 Trend analysis; Working Group Bayesian state space analysis of trends Loggerhead Western National Marine 2009 LDM North Fisheries Service Atlantic Southeast Fisheries Science Center DA with SQE,i Loggerhead Western Conant et al.
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sufficient to prevent loggerhead sea turtles extinction. is very uncertain due in part to large uncertainty in our knowledge of loggerhead life history." Nine distinct population "This approach (LDM)
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WHAT IS AN ASSESSMENT? Population assessments seek to measure the current status, evaluate trends over previous years, and predict the status of populations under various management scenarios by quantitatively evaluating population abundance and assessing such demographic parameters as productivity and survivorship (called "vital rates" that indicate the potential for change in a population)
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h This was also the case for the 1998 Turtle Expert Working Group assessment for these species, where potential biological removal (PBR) and strandings trend analysis were sug gested as methods for setting limits on strandings to trigger management action.
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predict the effect of future management practices on the population. As in almost all marine species, population assessments of sea turtles are challenging because of a lack of critical data or a difficulty in accessing data.
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Assessment of sea-turtle population status and trends is conducted according to the requirements of the Endangered Species Act and through expert working groups, recovery plan teams, and biological review teams convened by NMFS Fisheries Science Centers. Worldwide, fish-stock assessments usually are prepared by fishery agencies and -- in the United States -- stock-assessment teams associated with NMFS and regional management councils.
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Observed and potential changes in seaturtle populations through time need to be assessed with agestructured models to determine population wide status accurately and to diagnose causes of population change. Like wise, heuristic evaluation of possible futures under datapoor conditions has limited utility because management often requires "highresolution" results -- accurate and precise predictions of effect so that it can set take regulations and evaluate the outcomes of targeted management actions.
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From page 23... ...
Robust assessment of the status and trend of a loggerhead sea turtle population suitable for population assessment and conservation management planning requires additional information and depends on sampling of the entire demographic structure of a population resident in the foraging grounds and on deriving a range of estimates of key demo graphic parameter of the population. The spatial and temporal variation in nesting activity of the north western Atlantic loggerhead population that nests along the Atlantic coast of Florida has been monitored for more than 20 years.
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We have bits and pieces of the information but lack the specific census and mortality data necessary to characterize and monitor trends for these populations." In this case, longterm abundance estimates without accompanying estimates of key demographic parameters were not sufficient to diagnose the cause(s) of the decline in nest numbers and to design suitable riskmitigation or populationrecovery strategies.
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The assessments of reproductive con dition support sex determination and direct estimates of breeding rates. Not only is the spatial and temporal variation in SGBR loggerhead nesting abundance well known but so are key demographic parameters, such as sexspecific and ageclassspecific survival probabilities, sexspecific breed ing rates, and trends in sexspecific and ageclassspecific foraginghabitat abundance estimates (Chaloupka and Limpus, 2001, 2002; Chaloupka, 2003a)
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The shared responsibility means that cooperation between the agencies in the management of seaturtle populations is critical. The two agencies have a history of cooperation, as in the codevelopment of recovery plans mandated by the Endangered Species Act (e.g., National Marine Fisheries Service and U.S.
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Chapter 5 discusses demographic parameters of sea turtles and what is known about them and methods and research needs. Chapter 6 discusses the importance of and methods for integrating demographic information with abundance estimates.
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ASSESSMENT OF SEA-TURTLE STATUS AND TRENDS issues that cut across many aspects of population assessments, includ ing data management, education and training, the permit process, and opportunities for coordination at various levels. Chapter 8 provides the committee's major conclusions and recommendations.
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