1,721,064 research outputs found
AN EVALUATION OF NEST RELOCATION AS A LOGGERHEAD SEA TURTLE (Caretta caretta) MANAGEMENT TECHNIQUE IN NORTH CAROLINA
No full textA network of volunteers, under the guidance of the North Carolina Sea Turtle Protection
Program, monitors and protects loggerhead nests laid on state beaches. Although volunteers are
encouraged to allow nest incubation to proceed naturally and with minimal intervention, some
volunteers will relocate freshly laid nests that are threatened by possible inundation by high
tides, heavy beach traffic, or under a sloughing escarpment.
Nest relocation may have negative effects: it may reduce hatching success, alter incubation
duration, and reduce hatchling fitness. Thus an evaluation of hatching success and incubation
duration at nesting areas under the protection of the NC Sea Turtle Protection Program is
warranted.
My objective for the evaluation was to use loggerhead sea turtle (Caretta caretta) nest activity
data from four high-density North Carolina nesting areas – Bald Head Island, Cape Lookout
National Seashore, Cape Hatteras National Seashore, and Topsail Island – to assess statistically
the management technique of nest relocation in North Carolina. Using 1997 to 2001 data,
provided by the North Carolina Sea Turtle Protection Program, I evaluated hatching success and
incubation duration among in-situ nests, relocated nests, and in-situ nests affected by tidal
inundation.
During each of the five years, 1997 to 2001, the average number of nests moved on the study’s
four North Carolina nesting areas approached 40 to 60 percent. The evaluation of hatching
success showed a tendency of more loggerhead hatchlings hatching in in-situ nests than in
relocated nests. Also, the evaluation indicated a tendency of in-situ nests having longer
incubation durations than relocated nests.
The evaluation showed relocated nests might have shorter incubation periods, and thus present
nest relocation techniques in North Carolina might be skewing northern sub-population sexratios
more in favor of female hatchling production.
I formulated a series of nest relocation recommendations with the evaluation results: use nest
relocation as a last resort, only relocate nests that will be over-washed daily by high tides, do not
base nest relocation measures on previous summer storms, and do not relocate nests in heavy
foot traffic areas
Tracking terrapins through genetic analysis: Multilocus assignment tests shed light on origin of turtles sold in markets
No full textDiamondback terrapins (Malaclemys terrapin) are currently sold for human
consumption in many large cities in the United States. Some Asian cultural groups utilize
large numbers of terrapins, both regionally and world-wide, as a protein source. Terrapin
populations face many prevalent problems including predation by both native and non-native
predators, and anthropogenic disturbances (such as habitat destruction, roadkill, and bycatch in blue crab traps). The additional anthropogenic dilemma of terrapins sold in fish markets is particularly troubling when added to the long list of widespread disturbances. Terrapin harvesting is restricted in each state throughout the Atlantic and Gulf coastal range of the
species; however, enforcement of these restrictions is weak. The objective of our study was to determine the origin of terrapins sold in New York City’s Fulton Fish Market. In 2004, we collected blood samples from 63 individual terrapins confiscated from illegal sellers in
the Market. Some of these terrapins were released off the coast of Maryland, based on the
belief that the terrapins were originally harvested in the Chesapeake Bay. In this study, we
used microsatellite DNA variation to test the hypothesis that M. terrapin collected in the
Market are from the Coastal Mid-Atlantic terrapin metapopulation. We extracted DNA from
blood samples, performed PCR, and screened each turtle at 12 polymorphic microsatellite
DNA loci developed for bog turtles (Glyptemys muhlenbergii). Statistical analyses relied on
assignment tests to determine the most likely region of origin for each terrapin to the
metapopulation and subpopulation level. Many of the terrapins were assigned to the
Chesapeake Bay metapopulation (or subpopulations in Maryland); however, some terrapins
were assigned to the Coastal Mid-Atlantic or the Coastal Carolina region. Rules and
regulations (and the enforcement of these rules) need to be improved to adequately protect
terrapins from direct harvest
Managing the North Carolina Blue Crab Fishery: Engaging Fishermen in the Analysis of Soft and Peeler Crab Regulations
No full textIn September of 2005, the North Carolina Marine Fisheries Commission approved regulations in the blue crab fishery for reducing wasteful fishing practices and preserving the spawning stock. Interviews of soft and peeler crab fishermen in Carteret County, North Carolina revealed the perceived effects of these and other regulations on their individual operations and on the health of the fishery as a whole. The results of these interviews are discussed in the following report. Additionally, the extent to which the 1998 and 2004 North Carolina Blue Crab Fishery Management Plans reflect the major findings of the interviews is considered and recommendations for future management plans are offered
Investigation of Seal and Dogfish Depredation in Gillnets
No full textImpacts of predation by seals and dogfish on fish caught in gillnets has been largely neglected. This is important in Cape Cod’s Fixed Gear Sector because all discarding associated with predation is counted against the sector’s Total Allowable Catch (TAC). This results in a loss of profits for fishermen within the sector. Between June 3rd and July 3rd 2007, sixty-one gillnet hauls were observed during regular commercial fishing activities in order to investigate predation rates of both species. Allometric regression was used in tandem with weight conversion factors to determine the estimated total weight of eaten and discarded fish in each haul. Spatial relationships and predation rates relative to certain environmental variables were also investigated. Results showed that approximately 2,500 lbs of fish was discarded from a total catch weight of nearly 130,000 lbs because of predation by both seals and dogfish. This represented an estimated 64,000, signifying a 3.53% loss of the fishermen’s gross profits. The biggest monetary loss was associated with the monkfish catch. With regard to environmental variable significance, there was a correlation between increased net soak duration and increased predation by both species. The water depth at which nets were set was also significant; however, this was only in relation to seal predation with predation events generally occurring between 25 and 31 fathoms. Seal events occurred mainly over clay and, dogfish over a sandy substrate, however, bias may exist in these latter findings based on the predominance of nets being set on sand. Furthermore, spatial investigations highlighted that fishing practices were taking place in closed and restricted areas. Overall, results suggest that amendments need to be made to the NEFMP to ensure a reduction in discarding associated with predation by seals and dogfish. Also, although the gross profit loss appeared low, further investigations involving net profit loss would place these findings in greater context
Bycatch and foraging ecology of sea turtles in the Eastern Pacific
No full textSea turtles are long lived marine species that are currently endangered because their life history and population dynamics hinder them from withstanding modern anthropogenic threats. Worldwide, fisheries bycatch in on the major threats to the survival of sea turtles and that is also the case in the Eastern Pacific. To establish regional conservation priorities for the mitigation of bycatch, it is essential to first obtain a comprehensive picture of the regional sea turtle bycatch situation. This comprehensive analysis was lacking for the Eastern Pacific; therefore one component of this dissertation (the first chapter) is focused on delivering a regional bycatch analysis for the Eastern Pacific. A literature review was conducted to obtain numbers of turtles captured, frequencies, bycatch and mortality rates per species and country in trawl, longline, and gillnet fisheries, and to compile results of mitigation measures. Moreover, estimates for current annual capture rates in trawl fisheries were obtained and compared with population numbers. This regional bycatch used all the information compiled and synthesized to give conservation priorities at the regional level. The review underlines the high bycatch rates in trawls for Costa Rica, Guatemala, and El Salvador and the detrimental impact that these captures could have specially for hawksbill Eretmochelys imbricata due to its reduced population numbers and for green turtle Chelonia mydas due to its highest mortality rate. It also emphasizes the continuous lack of use of TEDs as a bycatch mitigation measure. In longline fisheries, the review identifies the high bycatch rates in pelagic longline fisheries of Costa Rica, Ecuador, and Nicaragua in a global context but given that olive ridley Lepidochelys olivacea is the most common species captured in these countries, it highlights the capture of loggerhead Caretta caretta and leatherback Dermochelys coriacea off Peru and Chile due to their small population numbers. Bottom longlines have high mortality rates compared with pelagic longlines in the region and the review identifies a need for further research in this area due to the scarce information but high mortality rates. The review also noted that some mitigation measures for pelagic longlines like circle hooks and hooks with appendages could bring improvements in the mitigation of bycatch in longline fisheries in the region, there is still considerable work to be done in technology transfer, sea turtle handling, and estimates of post-release mortality rates. For gillnet fisheries, the most important highlight is how little information exists for the region given the high rates of bycatch for sea turtles in this gear. However, the difficulties of studying bycatch in highly dynamic and artisanal fisheries are recognized as the major impediment for this situation. Nevertheless, the high bycatch rates in areas where sea turtles congregate in high numbers like in foraging grounds for loggerhead in Baja California, Mexico and for greens in Paracas and Sechura, Peru, calls for either gear modifications (which has not been that successful), change of gear, or areas closed for gillnets. The second half of the dissertation is focused on foraging ecology of oceanic sea turtles in the Southeast Pacific Ocean. Sea turtles in the oceanic stage are the least known stage due to the difficulty of accessing these individuals. However, it is a very important stage in the life cycle and can be critical for the population dynamics of sea turtles as some population models have shown. Therefore, this dissertation is filling a gap in the life cycle of sea turtle populations in the Eastern Pacific. To study foraging ecology, we used Stable Isotope Analysis (SIA) of turtle tissues as well as potential prey items from the oceanic realm. SIA is a great tool because it gives an integrated view, from days to weeks, of prey from a consumer tissue. SIA also can be used to link consumers to habitats when elements that have spatial trends are used. In chapter two, we investigate the foraging ecology of three species of sea turtles to compare trophic status and to observe if spatial patterns were shown in the SIA signatures of sea turtles. To our knowledge this is the first study employing SIA to research the ecology of three species of sea turtles from the same time and space. Our results show that spatial patterns in delta15N and delta13C were observed in sea turtle's tissues as correlations with latitude. We also found that loggerhead's signatures differed significantly from green and olive ridleys, especially in terms of delta15N. Loggerheads had higher values of delta15N and also a wider nitrogen trophic niche. Greens and olive ridleys were similar in isotopic nitrogen values but they were significantly different in carbon. When analyzing a smaller group of animals captured in a more restricted area, nitrogen differences were not found which suggests that latitudinal spatial patterns play an important role in the nitrogen signature. On the contrary, carbon signatures still differed among turtles in the restricted area which suggest that the inshore-offshore trend is strong and made us conclude that loggerheads are restricted to oceanic areas but that greens and olive ridleys could be using both coastal and oceanic areas.In chapter three, we conduct a mixing model analysis using the Bayesian program SIAR to identify the most important prey items for green, olive ridley, and loggerhead off Peru. Also, we wanted to identify the contribution of longline baits in the diet of oceanic turtles. The analysis was restricted to the central zone of our study area to avoid spatial trends in nitrogen. To use as sources in the model, we collected potential prey items offshore Peru during trips on longline fishing vessels and obtained their stable isotope signatures. Results from our mixing models show that for greens and olive ridleys, crustaceans, mollusks, and coastal Ulva (indicator of coastal prey) were the only important food items. In the case of greens, crustaceans had a very high proportional contribution and due to the fact that nitrogen values of crustaceans were the lowest ones among the sources it seems that greens would be eating in a lower trophic level. The importance of coastal Ulva for greens and olive ridleys is a confirmation of our findings from chapter two where we suggest that these two species could be using oceanic as well as coastal areas. Results for loggerheads showed cnidarians, mollusks, mackerel and squid bait as foraging items and highlights the differences among this species and the other two. The lack of importance of coastal Ulva again suggests that loggerheads remain only in oceanic areas off Peru. Moreover, the importance of mackerel and squid, the most common longline baits, suggests this species is the one interacting the most with longline fisheries and that cumulative effect of multiple interactions could have a detrimental effect in this population.</p
The Effects of Dredging and Trawling on Continential Shelf Sediment Biochemistry
No full textThe effects of fishing gear on the seabed are well documented. This study specifically
investigates the use of dredges and trawls, which are two of the most commonly towed fishing
gears both in the U.S. and abroad. These gears are both "active" bottom-contact fishing gear,
which means large bag nets, weighing nearly 1500 pounds empty, are towed by fishing vessels
and dragged across the seafloor to catch demersal species such as oyster, crabs, clams, halibut,
flounder, cod, and shrimp. The effects of these gears on benthic habitats have been much studied
and include fish and invertebrate mortality (target and non-target species), loss of habitat,
reduced habitat complexity and community diversity, and a reduction in productivity.
Conversely, the impacts of dredging and trawling on sediment biogeochemistry have been
seldom considered, but could have far-reaching implications when experimental results are
extrapolated to larger scales. This study extensively reviews the current and available research on
the effects of mobile fishing gear use on sediment biogeochemistry, processes, and sedimentary
rnicroenvironments. Specifically, I wanted to answer the following questions: With the
assumption ofa high frequency ofdredging and trawling on the world's continental shelves,
does mobile fishing gear resuspend and subsequently oxidize carbon that would otherwise be
stored in shelf sediments? If so, could this be an unrecognized and significant source ofcarbon
dioxide to the water column and consequently the atmosphere thereby contributing to global
warming?
An extensive literature review yielded only four scientific studies addressing the biogeochemical
implications (for C, N, P, and Si) but none of them tackled the effects to carbon beyond the
experimental scale. Consequently, with the assistance of Dr. Richard Barber (Duke University), I
created a carbon box model to estimate the carbon contribution (using a 1m^2 study area) induced
by dredging and trawling relative to a background sea surface carbon value of 2000mM C/m^3.
The goal was to establish an upper bound estimate (or maximum) for the amount of CO2 that
dredging and trawling could potentially contribute to the atmosphere and to global warming
processes. Calculations were done for 50m, 100m, and 200m water depths using total export
production values of lOgC/m^2 and 50gC/m^2 and with values of 10% and 50% of that production
reaching the seafloor. Additionally, we assumed that 100% of the C reaching the seafloor was
oxidized and trapped in the sediments and 100% of that was resuspended by the fishing gear.
The value of lOgC/m^2 represents a representative estimate to how much carbon sinks to
substrate, while 50gC/m^2 is wildly high and was used to establish an upper bounds for the
estimate. The results yielded an approximately 1.5% addition to the carbon in sea surface waters
and subsequently the atmosphere; this illustrates that although there is a net transfer of carbon
dioxide from the water column to the atmosphere, dredging and trawling is not a significant and
unaccounted for source of CO2 and thus does not influence global warming
An Assessment of Sea Turtle, Marine Mammal and Seabird Bycatch in the Wider Caribbean Region
No full textSea turtles, marine mammals and sea birds are vulnerable to higher mortality rates as a direct function of incidental capture (bycatch) in marine fisheries. Their migratory behavior exposes them to multiple fishing gear types and fishing practices and efforts to understand the rates of interaction between these taxa and fishing necessarily entails analysis of data over large spatial areas (ocean-basin) and multiple types of fishing activities. The acquisition the requisite data, however, requires considerable resources and many regions in the world are data-poor with respect to bycatch, including the Wider Caribbean Region (WCR) in the west central Atlantic Ocean basin. This dissertation presents the results of multiple strategies used to assess sea turtle, marine mammal and seabird bycatch in the WCR, with a particular focus on sea turtle bycatch. The research incorporated a synthetic review of the literature, expert consultation, statistical techniques, and geospatial analyses to assess the bycatch seascape for the region. I conclude that sea turtle bycatch in the WRC is significantly linked to turtle rookeries, especially those on the continental land mass and in the southern section of the Caribbean basin, in large part because of the near shore artisanal nature of the fisheries and the importance of these habitats for foraging and reproduction. The limited information on marine mammal bycatch does not permit robust inferences, but it clearly identifies threats to at least one vulnerable marine mammal species, the tucuxi (Sotalia fluviatilis). Information on seabird bycatch was even more limited; the most vulnerable seabird populations occur in the higher latitudes (temperate zones) while the seabird populations in the WCR face significant threats from habitat loss and over-exploitation. This dissertation proposes specific recommendations for improving and advancing the information base for a regional, ecosystem-level management and mitigation of bycatch.</p
Integration of Physical Oceanography with Spatio-Temporal Patterns of Stranded Sea Turtles in North Carolina
No full textThe conservation status of sea turtles warrants research on their mortality rates
(Turtle Expert Working Group 1998). Stranded carcasses document mortality but
represent an unknown fraction of total number of dead turtles at-sea (Murphy and
Hopkins-Murphy 1989, Epperly et al. 1996). In addition to water temperature, tidal
forcing, decomposition rates, scavenging rates, and the spatio-temporal distributions of
turtles and mortality sources, wind and water current regimes probably play a major role
in the stranding of carcasses on beaches. Fifteen years of hourly wind speed data,
recorded off the North Carolina coast, were transformed into vectors, converted into wind
stress magnitude and direction values, and averaged by month. Near-shore surface
currents were then modeled for the South Atlantic Bight via a three-dimensional physical
oceanographic model (Werner et al. 1999). Estimated currents and particle tracks were
compared to the spatial locations of sea turtle carcasses stranded along ocean-facing
beaches of North Carolina. The seasonal development of along-shelf flow coincided with
increased numbers of recorded strandings in late spring and early summer. The model
also predicted net offshore flow of surface waters during winter, typically the season with
the fewest relative strandings. Modeled lagrangian drogues were retained in shallow (< 20m) bathymetric contours, indicating that turtles killed only very close to the shore may be most likely to strand. During seasons when net along-shelf flow was present, turtles
were likely to have died "upstream" from the residual current. A reevaluation of oceanic
drift bottle experiments may also provide a reasonable upper bound to describe how far
carcasses could theoretically travel and how likely those carcasses could make landfall
from points offshore. Though qualitative, this research a.) provides a starting point for
more robust analyses and b.) demonstrates that stranding research requires an
understanding of ocean physics in addition to sources of mortality
MARINE MAMMALS AND THE EFFECTS OF NOISE: FACTS ABOUT ACOUSTIC SIGNALS AND THE POTENTIAL IMPACTS OF HUMAN SOUND SOURCES
No full textBoth natural and human-generated sounds fill the marine environment. Biological processes generate natural sound such as wind, rain, and waves. Humans intentionally produce sound when using sonar or conducting seismic surveys as tools to visualize the underwater world. They produce sound unintentionally through oil and gas exploration and extraction, ocean experiments, and shipping. As sound increases in the ocean, scientists and the general public become increasingly concerned about the potential impact of sound on marine mammals. With these concerns in mind, I undertook a project to provide public outreach and education by producing a brochure for National Oceanic and Atmospheric Administration (NOAA), The American Zoo and Aquarium Association (AZA), Consortium for Oceanographic Research and Education (CORE),
and the Marine Mammal Commission (MMC) to distribute during their series of public
lectures around the United States to increase public knowledge about human-generated noise and marine animals
A Preliminary Delineation of Shark Nursery Grounds in Two South Carolina Estuaries
No full textI hypothesize that urbanization Murrells Inlet will affect the total number of
elasmobranches present and the species diversity of elasmobranchs. I believe predation
is the controlling factor for newborn sharks and young juveniles, and so I would expect to
find those individuals in the areas least accessible to adult sharks. This idea is supported
by Gilliam and Fraser (1987) who looked at foraging behavior in response to predation
pressure. They found fishes will move to the habitats that afford them the greatest
chances of survival. However, once animals grow in size, and the risk of being eaten
becomes substantially less, they move to areas that are less environmentally stressful
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