The effect of Peruvian small-scale fisheries on sunfishes (Molidae).

Reports were compiled of sunfish (family Molidae) by-catch in Peruvian small-scale fisheries and sunfish by-catch rates were estimated using data from shore-based and onboard monitoring programmes. A total of 114 sunfishes were reported in the longline and gillnet fisheries along the Peru coast from 2005 to 2017. Systematic monitoring effort of small-scale gillnets leads to an estimate of between 23 and 352 individuals captured annually by the fleet fishing from the northern port of Salaverry and central ports of Ancon and Chorrillos and suggests that the actual number captured by the Peruvian gillnet fleet is in the thousands of individuals. Thus, Peruvian small-scale fisheries have the potential to greatly affect populations of these still poorly studied species. Moreover, new occurrence locations are reported for the newly described Mola tecta, which was only observed south of 11° S. Because of physical similarities among Mola species it was difficult to identify sunfishes to the species level and thus further studies (e.g., genetics) will be required to provide more detailed information on individual species vulnerability to by-catch in Peruvian waters.

Biomarkers reveal sea turtles remained in oiled areas following the Deepwater Horizon oil spill.

Assessments of large-scale disasters, such as the Deepwater Horizon oil spill, are problematic because while measurements of post-disturbance conditions are common, measurements of pre-disturbance baselines are only rarely available. Without adequate observations of pre-disaster organismal and environmental conditions, it is impossible to assess the impact of such catastrophes on animal populations and ecological communities. Here, we use long-term biological tissue records to provide pre-disaster data for a vulnerable marine organism. Keratin samples from the carapace of loggerhead sea turtles record the foraging history for up to 18 years, allowing us to evaluate the effect of the oil spill on sea turtle foraging patterns. Samples were collected from 76 satellite-tracked adult loggerheads in 2011 and 2012, approximately one to two years after the spill. Of the 10 individuals that foraged in areas exposed to surface oil, none demonstrated significant changes in foraging patterns post spill. The observed long-term fidelity to foraging sites indicates that loggerheads in the northern Gulf of Mexico likely remained in established foraging sites, regardless of the introduction of oil and chemical dispersants. More research is needed to address potential long-term health consequences to turtles in this region. Mobile marine organisms present challenges for researchers to monitor effects of environmental disasters, both spatially and temporally. We demonstrate that biological tissues can reveal long-term histories of animal behavior and provide critical pre-disaster baselines following an anthropogenic disturbance or natural disaster.

Determining origin in a migratory marine vertebrate: a novel method to integrate stable isotopes and satellite tracking.

Stable isotope analysis is a useful tool to track animal movements in both terrestrial and marine environments. These intrinsic markers are assimilated through the diet and may exhibit spatial gradients as a result of biogeochemical processes at the base of the food web. In the marine environment, maps to predict the spatial distribution of stable isotopes are limited, and thus determining geographic origin has been reliant upon integrating satellite telemetry and stable isotope data. Migratory sea turtles regularly move between foraging and reproductive areas. Whereas most nesting populations can be easily accessed and regularly monitored, little is known about the demographic trends in foraging populations. The purpose of the present study was to examine migration patterns of loggerhead nesting aggregations in the Gulf of Mexico (GoM), where sea turtles have been historically understudied. Two methods of geographic assignment using stable isotope values in known-origin samples from satellite telemetry were compared: (1) a nominal approach through discriminant analysis and (2) a novel continuous-surface approach using bivariate carbon and nitrogen isoscapes (isotopic landscapes) developed for this study. Tissue samples for stable isotope analysis were obtained from 60 satellite-tracked individuals at five nesting beaches within the GoM. Both methodological approaches for assignment resulted in high accuracy of foraging area determination, though each has advantages and disadvantages. The nominal approach is more appropriate when defined boundaries are necessary, but up to 42% of the individuals could not be considered in this approach. All individuals can be included in the continuous-surface approach, and individual results can be aggregated to identify geographic hotspots of foraging area use, though the accuracy rate was lower than nominal assignment. The methodological validation provides a foundation for future sea turtle studies in the region to inexpensively determine geographic origin for large numbers of untracked individuals. Regular monitoring of sea turtle nesting aggregations with stable isotope sampling can be used to fill critical data gaps regarding habitat use and migration patterns. Probabilistic assignment to origin with isoscapes has not been previously used in the marine environment, but the methods presented here could also be applied to other migratory marine species.

Identifying patterns in foraging-area origins in breeding aggregations of migratory species: Loggerhead turtles in the Northwest Atlantic.

Population assessments conducted at reproductive sites of migratory species necessitate understanding the foraging-area origins of breeding individuals. Without this information, efforts to contextualize changes in breeding populations and develop effective management strategies are compromised. We used stable isotope analysis of tissue samples collected from loggerhead sea turtles (Caretta caretta) nesting at seven sites in the Northern Recovery Unit (NRU) of the eastern United States (North Carolina, South Carolina and Georgia) to assign females to three separate foraging areas in the Northwest Atlantic Ocean (NWA). We found that the majority of the females at NRU nesting sites (84.4%) use more northern foraging areas in the Mid-Atlantic Bight, while fewer females use more proximate foraging areas in the South Atlantic Bight (13.4%) and more southerly foraging areas in the Subtropical Northwest Atlantic (2.2%). We did not find significant latitudinal or temporal trends in the proportions of NRU females originating from different foraging areas. Combining these findings with previous data from stable isotope and satellite tracking studies across NWA nesting sites showed that variation in the proportion of adult loggerheads originating from different foraging areas is primarily related differences between recovery units: individuals in the NRU primarily use the Mid-Atlantic Bight foraging area, while individuals from the three Florida recovery units primarily use the Subtropical Northwest Atlantic and Eastern Gulf of Mexico foraging areas. Because each foraging area is associated with its own distinct ecological characteristics, environmental fluctuations and anthropogenic threats that affect the abundance and productivity of individuals at nesting sites, this information is critical for accurately evaluating population trends and developing effective region-specific management strategies.

Common metabolic constraints on dive duration in endothermic and ectothermic vertebrates.

Dive duration in air-breathing vertebrates is thought to be constrained by the volume of oxygen stored in the body and the rate at which it is consumed (i.e., "oxygen store/usage hypothesis"). The body mass-dependence of dive duration among endothermic vertebrates is largely supportive of this model, but previous analyses of ectothermic vertebrates show no such body mass-dependence. Here we show that dive duration in both endotherms and ectotherms largely support the oxygen store/usage hypothesis after accounting for the well-established effects of temperature on oxygen consumption rates. Analyses of the body mass and temperature dependence of dive duration in 181 species of endothermic vertebrates and 29 species of ectothermic vertebrates show that dive duration increases as a power law with body mass, and decreases exponentially with increasing temperature. Thus, in the case of ectothermic vertebrates, changes in environmental temperature will likely impact the foraging ecology of divers.

Mother-egg stable isotope conversions and effects of lipid extraction and ethanol preservation on loggerhead eggs.

Carbon and nitrogen stable isotope (δ(13)C and δ(15)N) analysis has been used to elucidate foraging and migration behaviours of endangered sea turtle populations. Isotopic analysis of tissue samples from nesting females can provide information about their foraging locations before reproduction. To determine whether loggerhead (Caretta caretta) eggs provide a good proxy for maternal isotope values, we addressed the following three objectives: (i) we evaluated isotopic effects of ethanol preservation and lipid extraction on yolk; (ii) we examined the isotopic offset between maternal epidermis and corresponding egg yolk and albumen tissue δ(13)C and δ(15)N values; and (iii) we assessed the accuracy of foraging ground assignment using egg yolk and albumen stable isotope values as a proxy for maternal epidermis. Epidermis (n = 61), albumen (n = 61) and yolk samples (n = 24) were collected in 2011 from nesting females at Wassaw Island, GA, USA. Subsamples from frozen and ethanol-preserved yolk samples were lipid extracted. Both lipid extraction and ethanol preservation significantly affected yolk δ(13)C, while δ(15)N values were not altered at a biologically relevant level. The mathematical corrections provided here allow for normalization of yolk δ(13)C values with these treatments. Significant tissue conversion equations were found between δ(13)C and δ(15)N values of maternal epidermis and corresponding yolk and albumen. Finally, the consistency in assignment to a foraging area was high (up to 84%), indicating that these conversion equations can be used in future studies where stable isotopes are measured to determine female foraging behaviour and trophic relationships by assessing egg components. Loggerhead eggs can thus provide reliable isotopic information when samples from nesting females cannot be obtained.