Potential causes of mortality for horseshoe crabs (Limulus polyphemus) during the biomedical bleeding process

Biomedical companies catch and bleed horseshoe crabs for the production of Limulus amebocyte lysate (LAL), a product used for protecting public health (Berkson and Shuster, 1999). LAL is a clotting agent, derived solely from horseshoe crab blood cells, which is used to detect the presence of pathogenic gramnegative bacteria in injectable drugs and implantable medical and dental devices (Mikkelsen, 1988; Novitsky, 1991). In addition, LAL is used in many diagnostic tests for such illnesses as gram-negative bacterial meningitis and typhoid fever (Ding and Ho, 2001). Because the LAL test allows one to detect femtogram levels of endotoxin (Ding and Ho, 2001), it is the most effective test for detecting endotoxin contamination, and its increasing use in medical and pharmaceutical laboratories makes it a highly valued product

A production modeling approach to the assessment of the horseshoe crab (Limulus polyphemus) population in Delaware Bay

Horseshoe crab (Limulus polyphemus) is harvested commercially, used by the biomedical industry, and provides food for migrating shorebirds, particularly in Delaware Bay. Recently, decreasing crab population trends in this region have raised concerns that the stock may be insufficient to fulfill the needs of these diverse user groups. To assess the Delaware Bay horseshoe crab population, we used surplus production models (programmed in ASPIC), which incorporated data from fishery-independent surveys, fishery-dependent catch-per-unit-of-effort data, and regional harvest. Results showed a depleted population (B2003/=0.03−0.71) BMSY and high relative fishing mortality /FMSY=0.9−9.5). Future harvest (F2002strategies for a 15-year period were evaluated by using population projections with ASPICP software. Under 2003 harvest levels (1356 t), population recovery to BMSY would take at least four years, and four of the seven models predicted that the population would not reach BMSY within the 15year period. Production models for horseshoe crab assessment provided management benchmarks for a species with limited data and no prior stock assessmen

Abundance of horseshoe crabs (Limulus polyphemus) in the Delaware Bay area

In recent years, increasing commercial landings of horseshoe crabs (Limulus polyphemus) along the Atlantic coast of the United States have raised concerns that the present resource is in decline and insufficient to support the needs of its user groups. These concerns have led the Atlantic States Marine Fisheries Commission (ASMFC) to implement a fishery management plan to regulate the harvest (ASMFC1). In order to properly manage any species, specific management goals and objectives must be established, and these goals depend on the resource users involved (Quinn and Deriso, 1999). Horseshoe crabs present a distinct resource management challenge because they are important to a diverse set of users (Berkson and Shuster, 1999)

Evaluating methods for estimating rare events with zero-heavy data: a simulation model estimating sea turtle bycatch in the pelagic longline fishery

Estimating rare events from zero-heavy data (data with many zero values) is a common challenge in fisheries science and ecology. For example, loggerhead sea turtles (Caretta caretta) and leatherback sea turtles (Dermochelys coriacea) account for less than 1% of total catch in the U.S. Atlantic pelagic longline fishery. Nevertheless, the Southeast Fisheries Science Center (SEFSC) of the National Marine Fisheries Service (NMFS) is charged with assessing the effect of this fishery on these federally protected species. Annual estimates of loggerhead and leatherback bycatch in a fishery can affect fishery management and species conservation decisions. However, current estimates have wide confidence intervals, and their accuracy is unknown. We evaluate 3 estimation methods, each at 2 spatiotemporal scales, in simulations of 5 spatial scenarios representing incidental capture of sea turtles by the U.S. Atlantic pelagic longline fishery. The delta-log normal method of estimating bycatch for calendar quarter and fishing area strata was the least biased estimation method in the spatial scenarios believed to be most realistic. This result supports the current estimation procedure used by the SEFSC

Effects of Blood Extraction on the Mortality of the Horseshoe Crab, Limulus polyphemus

Horseshoe crabs (Limulus polyphemus) are bled by biomedical companies for the extraction of Limulus Amoebocyte Lysate (LAL), a clotting agent used in the detection of endotoxins. In 1998, the Atlantic States Marine Fisheries Commission mandated that all biomedical companies collecting horseshoe crabs for the production of LAL study the horseshoe crab mortality rates resulting from the company\u27s blood extraction process. BioWhittaker, a Cambrex Company is one of the largest producers of LAL in the world. During the summer of 1999, bled and unbled horseshoe crabs were transported from BioWhittaker\u27s bleeding facility in Chincoteague, Virginia to the Virginia Seafood Agricultural Research and Extension Center\u27s aquaculture facility in Hampton, Virginia. At the aquaculture facility, they were kept in a tank and their survival was monitored for a period of two weeks. Mortality for bled crabs was 15%, while mortality for unbled crabs was 0%. Because of the importance of horseshoe crabs to a wide variety of interests, proper management requires monitoring and consideration of mortality effects on the population

Effects of blood extraction on horseshoe crabs (Limulus polyphemus)

Horseshoe crabs (Limulus polyphemus) are caught by commercial fishermen for use as bait in eel and whelk fisheries (Berkson and Shuster, 1999)—fisheries with an annual economic value of $13 to$17 million (Manion et al.1). Horse-shoe crabs are ecologically important, as well (Walls et al., 2002). Migratory shorebirds rely on horseshoe crab eggs for food as they journey from South American wintering grounds to Arctic breeding grounds (Clark, 1996). Horse-shoe crabs are also essential for public health (Berkson and Shuster, 1999). Biomedical companies bleed horse-shoe crabs to extract a chemical used to detect the presence of endotoxins pathogenic to humans in injectable and implantable medical devices (Novitsky, 1984; Mikkelsen, 1988). Bled horseshoe crabs are returned to the wild, subject to the possibility of postbleeding mortality. Recent concerns of overharvesting have led to conflicts among commercial fishermen, environmentalists acting on behalf of the shorebirds, and biomedical companies (Berkson and Shuster, 1999; Walls et al., 2002)

Correlation of Eastern Wild Turkey Poult:hen Ratios with Population Indices to Detect Reproductive Density Dependence

Knowledge of how density affects population growth is important for the harvest management of wild turkey. Unfortunately, available time-series are often too short for statistical detection of density dependence. The correlation between wild turkey recruitment and population size was assessed using data from 7 state wildlife agencies, circumventing the problem of short time-series by using multiple datasets. Correlation coefficients were calculated between surveyed poult:hen ratios and harvest-based population indices for 31 geographic or harvest management regions. Estimated correlation coefficients were tested for homogeneity to determine if an average correlation could be calculated. Correlation coefficients for the 29 regions ranged from -0.82 to 0.70. A Q-test for homogeneity indicated that correlation coefficients were similar enough to warrant averaging [Q=25.45, df = 28, P = 0.603]. The weighted average correlation coefficient (± standard error) was r = -0.30 ± 0.45. Population size accounted for little of the variation associated with production (r = 0.09). Graphical analysis indicated that a negative correlation between poult:hen ratios and population size tended to occur when the range of population sizes was large. Density dependence appears to have little effect on production. Density-independent models should have better success modeling wild turkey production, while density-dependent effects may have stronger influence on survival or immigration at low population sizes

Encouraging Critical Thinking about Advocacy

Advocacy is a common topic in the literature. All graduates in natural resource sciences will have to face decisions regarding advocacy at some time. Unfortunately, we do little to prepare them for those decisions. Much of the literature says either we all must be advocates or none of us should be advocates. The reality is that there are jobs for people who want to be advocates and jobs for people who don’t. It’s crucial that students start to think critically about the role they want advocacy to play in their future. In this workshop we will introduce the participants to an exercise that quickly moves students beyond avoiding advocacy to a point where they relate it to their own values. Objectives are to (1) Discuss how advocacy is portrayed in the literature; (2) Discuss how students think about advocacy; (3) Discuss what should be our goals regarding advocacy and students; (4) Present methods and exercises to encourage students to think critically about advocacy; and (5) Discuss alternative approaches. Audience participation will be ensured because we will break into small groups (about four people per group) and do an exercise requiring everyone’s involvement. As this is such a controversial topic, it is bound to bring nearly everyone into the discussion. The discussions will be facilitated to encourage everyone’s participation

A Model For Assessing The Likelihood Of Self-Sustaining Populations Resulting From Commercial Production Of Triploid Suminoe Oysters (Crassostrea Ariakensis) In Chesapeake Bay

Culture of a non-native species, such as the Suminoe oyster (Crassostrea ariakensis), could offset the harvest of the declining native eastern oyster (Crassostrea virginica) fishery in Chesapeake Bay. Because of possible ecological impacts from introducing a fertile non-native species, introduction of sterile triploid oysters has been proposed. However, recent data show that a small percentage of triploid individuals progressively revert toward diploidy, introducing the possibility that Suminoe oysters might establish self-sustaining populations. To assess the risk of Suminoe oyster populations becoming established in Chesapeake Bay, a demographic population model was developed. Parameters modeled were salinity, stocking density, reversion rate, reproductive potential, natural and harvest-induced mortality, growth rates, and effects of various management strategies, including harvest strategies. The probability of a Suminoe oyster population becoming self-sustaining decreased in the model when oysters are grown at low salinity sites, certainty of harvest is high, minimum shell length-at-harvest is small, and stocking density is low. From the results of the model, we suggest adopting the proposed management strategies shown by the model to decrease the probability of a Suminoe oyster population becoming self-sustaining. Policy makers and fishery managers can use the model to predict potential outcomes of policy decisions, supporting the ability to make science-based policy decisions about the proposed introduction of triploid Suminoe oysters into the Chesapeake Bay

Students Teaching Students ­ A Unique Approach to Learning about the Complexities of Marine Resource Management

The National Mairne Fisheries Service and Virginia Tech have teamed to develop a unique learning experience for top undergraduate students from across the country. During the six week summer program, students learn about the complexities of an important marine resources issue first‐hand from the experts who know the subject the best. In the summer of 2006, six students learned about marine protected areas (MPAs), and in particular, methods to evaluate the effectiveness of MPAs. The six students traveled to two MPAs in different stages of development and met with MPA experts. We designed the summer program to share the summer students’ experiences and newly gained knowledge with students in classrooms around the world. To accomplish this, the summer students created a multi‐media, case study‐based, educational website that truly demonstrates the complexities of the MPA issue. Our long term goal is to create a library of diverse marine resources case studies, created by students, for students. Additional websites created during the previous summer are also currently available. The websites can be accessed at http://www.nmfs.vt.edu/casestudy.ht