Turtle Abundance Research Articles

When simple is better: Comparing two sampling methods to estimate green turtles abundance at coastal feeding grounds

Estimating population abundance of marine turtles on their feeding grounds is needed to implement effective conservation strategies, but is logistically challenging. In-water monitoring surveys on feeding grounds are costly, time-consuming, stressful to the animals (when capture is required), and typically requires complex analytical skills. Here, we compare two sampling methods to estimate abundance of green turtles on one of their major feeding grounds in the Egyptian Red Sea: a) snorkelling strip transect counts, a rarely used method on marine turtles; and b) capture–mark–recapture (CMR) using photo-identification. The main goals of this research were to: 1) identify the most cost-effective method to estimate in-water marine turtle abundance; and 2) provide the first abundance estimates for green turtles on their feeding grounds in the Red Sea. Both methods produced an average monthly abundance of approximately 30 turtles, with no significant difference between the two methodologies. The strip-transect method presented major logistical advantages, including easy field implementation, simple equipment, and only basic analytical skills. Furthermore, this method provided density estimates that can be used as index for population trends. However, limitations of this method included intensive field effort and potentially altered turtle behaviour due to the presence of the observers. By contrast, photo-identification and CMR models provided valuable information of population demography but required advanced analytical skills, did not provide a measure of density, and could prove challenging in areas where turtles are not acclimated to human presence. Our results suggest that the ease data collection and associated analysis of the strip transect method should be considered when implementing a monitoring program of wildlife to be used for management and conservation purposes.

Spatial variation in the littoral vertebrate community of a reservoir relative to physical and biological gradients.

Reservoirs possess gradients in conditions and resources along their long (deep-shallow) axis, but the response of littoral vertebrates (fish and turtles) to these gradients is poorly understood. We have quantified the littoral vertebrate communities throughout a small reservoir in Southeastern Ohio during July and August using traps, and related community composition to environmental variables using NMDS ordination. Ordination revealed that fish and turtles were broadly separated in ordination space, and three distinctly different environmental gradients were significantly associated with the underlying observed species abundances. Observed turtle abundance was explained by measurements of bathymetry, turbidity, and benthic resources, but none of these environmental variables were a reliable predictor of observed fish abundance. Temperature was a poor predictor of observed abundance for both fish and turtles independently, but when fish and turtles were considered together, it became apparent that there were cold areas of the reservoir where observed fish and turtle abundances were different than in other areas of the reservoir. These results suggest that the predictor (environmental) variables we used were appropriate for investigating turtle ecology in reservoirs, but that observed fish abundance is mediated by factors that were not modeled. The efficacy of using traps, the ecological implications of considering fish and turtles together as sympatric and potentially competing species, and directions for future study are discussed.

The Influence of Weather and Tides on the Land Basking Behavior of Green Sea Turtles (Chelonia mydas) in the Galapagos Islands

Abstract We monitored green sea turtle (Chelonia mydas) land basking behavior on Fernandina Island in the Galapagos Islands to determine the potential influence of tide level and weather on the presence and abundance of turtles. Using generalized linear models, we found that both presence and abundance of turtles were related to lower tide levels but that abundance was further related to higher air temperatures, reduced cloud cover, and falling tides; additionally, we recorded more males than have been found in other studies (males = 41.5% of observations). We hypothesize that haul out during low tide reduces energy expenditure of activities such as coming to the surface to breathe; however, more turtles take advantage of this behavior when conditions such as air temperature and cloud cover are more conducive to physiological benefits such as thermoregulation or acceleration of digestion.

Riparian Habitat Dissimilarities in Restored and Reference Streams are Associated with Differences in Turtle Communities in the Southeastern Piedmont

Few studies have assessed whether restored streams and riparian floodplains support reference communities of certain groups of freshwater organisms, such as turtles. This exploratory study compared turtle assemblages in six reference and six restored streams in the North Carolina Piedmont, which were assessed using standard trapping practices with baited hoop nets. We also quantified turtle-relevant habitat characteristics (structure, water quality, vegetation) through reach-scale surveys to assess potential differences in turtle composition. Turtle abundance at restored sites was more than twice that of references sites and trends existed in the distribution of turtle species, but neither abundance nor composition was found to be statistically different. Habitat characteristics that affect turtle communities were not equivalent between sites, with reference streams having higher canopy cover, and lower total phosphorus, dissolved oxygen and total suspended solids than restored streams. Mantel’s test and non-metric multidimensional scaling plots indicated that turtle composition was significantly correlated with habitat and vegetation, and that turtle communities were generally separated between restored and reference streams. These findings suggest a pattern that restored streams with riparian wetlands may provide more suitable habitat than reference streams for most southeastern Piedmont turtle species, but further studies are required to fully examine these patterns.

Jaguars (Panthera onca) increase kill utilization rates and share prey in response to seasonal fluctuations in nesting green turtle (Chelonia mydas mydas) abundance in Tortuguero National Park, Costa Rica

Jaguar (Panthera onca) predation of green turtles (Chelonia mydas mydas) is now a common occurrence in Tortuguero National Park, Costa Rica. The abundance of green turtles during nesting season ensures a constant provision of easy and predictable prey, however it is unknown to what extent jaguars consume turtle carcasses and how the jaguar population responds to limited turtle availability outside of nesting season. This study took advantage of the accessible nature of jaguar-predated turtle carcasses on Tortuguero Beach over a two year period (2011–2013), to provide a novel analysis of carcass utilization rates by jaguars and determine the effects of temporal fluctuations in green turtle nesting numbers. Camera traps were set-up on freshly predated turtles to capture jaguar activity across both Peak and Non Peak green turtle nesting seasons. Thirteen individual jaguars (five males, five females, three cubs) were captured returning to 77% of monitored turtle kills (60% Peak; 95% Non Peak). During Non Peak season, the number of jaguars per kill increased (H(1)=15.91, p<0.001) and total jaguar feeding time per kill also increased (H(1)=13.34, p<0.001). The propensity for tolerated scavenging or sharing during Non Peak season is illustrated by four adult jaguars captured interacting with a kill at separate times over two nights in October, 2012 (two males, two females). There were no significant differences between males and females, although there is a tendency for the latter to handle the prey to a greater extent. Although marine turtles may not to be a primary prey species, they play an important role in subsidizing the jaguars in this study. The increased kill utilization rates and prey sharing displayed by the jaguars, ensures optimal foraging during periods of low prey availability. These apparently atypical feeding behaviors may be unique to Tortuguero, however their prevalence across the jaguar's range should be considered.

Are nest-detection probability methods relevant for estimating turtle dove breeding populations? a case study in Moroccan agroecosystems

Knowing the population size of game is a basic prerequisite to determining adequate hunting management and conservation strategies and setting up appropriate hunting quotas. This study compared three methods complete count, capture–recapture and N-mixture modelling to estimate a turtle dove Streptopelia turtur breeding population using nest counts. We randomly sampled 143 fruit farms (60 orange orchards and 83 olive orchards) situated in an irrigated area in Morocco at the peak of breeding activity. We calculated the probability of detecting active turtle dove nests using information from two observers who independently searched the same sample plots. We found that (a) the capture–recapture method provided more precise results of nest abundance than N-mixture modelling, and that (b) the probability of nest detection was noticeably different between the two study orchards—higher in the orange orchards than in the olive orchards. Although these two methods are easy to implement and cost-effective for estimating population abundance on a large spatial scale, our results demonstrate that the resulting estimates are prone to bias depending on the tree height of the plantations. Of the three methods for estimating turtle dove abundance, complete counts were preferable for assessing population size. Using the complete counts, the density of turtle dove nests was found to be 2.96 nests/ha in the orange orchards and 0.93 nests/ha in the olive orchards. A density extrapolation to the entire surface area of the Tadla Region indicated a minimum breeding population size of 58,969 pairs (95 % confidence interval: 48,550–69,353).

Map Turtles of the Mermentau: Status Surveys of Forgotten Populations

The Mermentau River drainage in Louisiana has been largely ignored by turtle biologists, despite historical records of its turtle species. In particular, almost nothing is known about the range and abundance of the Sabine map turtle (Graptemys sabinensis) in the Mermentau drainage, which is frequently omitted from descriptions of the species' range. Four specimens of G. sabinensis were collected from the upper Mermentau in 1893 and 1894, but no trapping of the species has been conducted in the drainage since. We determined basking density and relative abundance among basking turtles for Sabine map turtles in the Mermentau drainage, including the Mermentau, Lake Arthur, and 5 major tributaries. We recorded turtles seen during boat surveys and in point-counts from bridges and other access points. The Mermentau and Bayou Plaquemine Brule had the highest basking densities, ranging from 14.0 to 34.5 G. sabinensis per river kilometer. Bayous des Cannes and Nezpique and Lake Arthur had intermediate average densities of 5.0–9.7 G. sabinensis per river kilometer and the river below Lake Arthur and the southern tributaries, Bayou Queue de Tortue and Lacassine Bayou, had the lowest average basking densities, ranging from 0.7 to 1.4 G. sabinensis per river kilometer. Sabine map turtles were the most abundant basking turtle on the Mermentau drainage, accounting for 73% of all turtles seen. Graptemys pseudogeographica, the false map turtle, accounted for only 0.2% of all turtles observed and is approaching extirpation in the drainage, likely due to the near total eradication of mussels that has resulted from extensive dredging of the Mermentau and its major tributary bayous.

Loggerhead sea turtle abundance at a foraging hotspot in the eastern Pacific Ocean: implications for at-sea conservation

The Pacific Coast of the Baja California Peninsula (BCP), Mexico, is a hotspot for for- aging loggerhead turtles Caretta caretta originating from nesting beaches in Japan. The BCP re- gion is also known for anthropogenic sea turtle mortality that numbers thousands of turtles annu- ally. To put the conservation implications of this mortality into biological context, we conducted aerial surveys to determine the distribution and abundance of loggerhead turtles in the Gulf of Ul- loa, along the BCP Pacific Coast. Each year from 2005 to 2007, we surveyed ca. 3700 km of transect lines, including areas up to 140 km offshore. During these surveys, we detected loggerhead turtles at the water's surface on 755 occasions (total of 785 loggerheads in groups of up to 7 turtles). We applied standard line-transect methods to estimate sea turtle abundance for survey data collected during good to excellent sighting conditions, which included 447 loggerhead sightings during ~6400 km of survey effort. We derived the proportion of time that loggerheads were at the surface and visible to surveyors based on in situ dive data. The mean annual abundance of 43 226 logger- head turtles (CV = 0.51, 95% CI range = 15 017 to 100 444) represents the first abundance estimate for foraging North Pacific loggerheads based on robust analytical approaches. Our density estimate confirms the importance of the BCP as a major foraging area for loggerhead turtles in the North Pacific. In the context of annual mortality estimates of loggerheads near BCP, these results suggest that up to 11% of the region's loggerhead population may perish each year due to anthro- pogenic and/or natural threats. We calculate that up to 50% of the loggerhead turtles residing in the BCP region in any given year will die within 15 yr if current mortality rates continue. This un- derscores the urgent need to minimize anthropogenic and natural mortality of local loggerheads.

Do roads reduce painted turtle (Chrysemys picta) populations?

Road mortality is thought to be a leading cause of turtle population decline. However, empirical evidence of the direct negative effects of road mortality on turtle population abundance is lacking. The purpose of this study was to provide a strong test of the prediction that roads reduce turtle population abundance. While controlling for potentially confounding variables, we compared relative abundance of painted turtles (Chrysemys picta) in 20 ponds in Eastern Ontario, 10 as close as possible to high traffic roads (Road sites) and 10 as far as possible from any major roads (No Road sites). There was no significant effect of roads on painted turtle relative abundance. Furthermore, our data do not support other predictions of the road mortality hypothesis; we observed neither a higher relative frequency of males to females at Road sites than at No Road sites, nor a lower average body size of turtles at Road than at No Road sites. We speculate that, although roads can cause substantial adult mortality in turtles, other factors, such as release from predation on adults and/or nests close to roads counter the negative effect of road mortality in some populations. We suggest that road mitigation for painted turtles can be limited to locations where turtles are forced to migrate across high traffic roads due, for example, to destruction of local nesting habitat or seasonal drying of ponds. This conclusion should not be extrapolated to other species of turtles, where road mortality could have a larger population-level effect than on painted turtles.

Spatial and temporal variability of immature green turtle abundance and somatic growth in Puerto Rico

Understanding conservation needs relies on robust estimates of key population parameters, such as survival, abundance and somatic growth. We investigated the somatic growth and abundance dynamics of 2 aggregations of immature green turtles, at Tortuga Bay and Puerto Manglar (Culebra, Puerto Rico), throughout 15 yr of capture-mark-recaptures. We used nonlinear models to investigate the effects of carapace length, sampling year, growth interval and the pres- ence of fibropapillomas on growth rates, and used the size-specific growth rate function to esti- mate how long turtles remain at each bay. Abundances were estimated and compared with time- specific growth rate functions, to infer density-dependency effects on somatic growth rates, and trends in abundance were evaluated by fitting generalized linear models. We found foraging site specific growth rates and report the highest mean somatic growth rate for green turtles in the wild (6.1 ± 1.7 cm yr �1 , at Puerto Manglar). The size-specific growth rate function was monotonic at both sites, with growth rates declining continuously with increasing carapace length. We inferred minimum ages at maturity of 14 and 22 yr, for Puerto Manglar and Tortuga Bay turtles, respec- tively. Throughout the 15 yr of this study there was a positive trend in aggregation size at Puerto Manglar (mean annual increase of 10.9%), which was not observed at Tortuga Bay. Our study highlights the influence of geography and habitat quality on somatic growth rates, and delivers robust demographic estimates valuable for local and regional assessments of the conservation sta- tus of the green turtle.

Interannual differences for sea turtles bycatch in Spanish longliners from Western Mediterranean Sea.

Recent studies showed that regional abundance of loggerhead and leatherback turtles could oscillate interannually according to oceanographic and climatic conditions. The Western Mediterranean is an important fishing area for the Spanish drifting longline fleet, which mainly targets swordfish, bluefin tuna, and albacore. Due to the spatial overlapping in fishing activity and turtle distribution, there is an increasing sea turtle conservation concern. The main goal of this study is to analyse the interannual bycatch of loggerhead and leatherback turtles by the Spanish Mediterranean longline fishery and to test the relationship between the total turtle by-catch of this fishery and the North Atlantic Oscillation (NAO). During the 14 years covered in this study, the number of sea turtle bycatches was 3,940 loggerhead turtles and 8 leatherback turtles, 0.499 loggerhead turtles/1000 hooks and 0.001014 leatherback turtles/1000 hooks. In the case of the loggerhead turtle the positive phase of the NAO favours an increase of loggerhead turtles in the Western Mediterranean Sea. However, in the case of leatherback turtle the negative phase of the NAO favours the presence of leatherback turtle. This contraposition could be related to the different ecophysiological response of both species during their migration cycle.

Factors influencing occurrence of a freshwater turtle in an urban landscape: a resilient species?

Context Species vary broadly in their ability to adapt to urbanisation. Freshwater turtles are vulnerable to the loss and degradation of terrestrial and aquatic habitat in urban environments. There have been few publications investigating impacts of urbanisation on freshwater turtles in Australia. Aims We investigated the effects of urbanisation on the distribution and abundance of the eastern long-necked turtle (Chelodina longicollis) in greater Melbourne. Methods We examined occurrence and relative abundance of C. longicollis at 55 wetlands across an urban–rural gradient in relation to site- and landscape-level factors. Occupancy was modelled using the program PRESENCE, and incorporated landscape and habitat covariates. A negative binomial regression model was used to examine the influence of landscape and habitat factors on relative abundance by using WinBUGS. Key results C. longicollis occupied 85% of the 55 wetlands we surveyed, and we found no evidence that wetland occupancy was influenced by the variables we measured. However, relative abundance was highest at wetlands with low water conductivity and heavy metal pollution, and in wetlands furthest from rivers. Conclusions C. longicollis appears to be resilient to urbanisation and is likely to persist in urban landscapes, possibly because of the creation of new wetlands in Australian cities. However, long-term studies focussed on demographic parameters, or survivorship, may elucidate as yet undetected effects of urbanisation. Although no specific management recommendations may be necessary for C. longicollis in urban areas at this time, this species may be in decline in non-urban areas as a result of climatic changes and wetland drying. Implications Our findings suggest that caution is required before drawing generalised conclusions on the impacts of urbanisation on turtles, as the effects are likely to be species-specific, dependent on specific ecology and life-history requirements. Further studies are required to ascertain these relationships for a wider array of species and over longer time spans.

Foraging areas differentially affect reproductive output and interpretation of trends in abundance of loggerhead turtles

Diet items and habitat constitute some of the environmental resources that may be used differently by individuals within a population. Long-term fidelity by individuals to particular resources exemplifies individual specialization, a phenomenon that is becoming increasingly recognized across a wide range of species. Less is understood about the consequences of such specialization. Here, we investigate the effects of differential foraging ground use on reproductive output in 183 loggerhead sea turtles (Caretta caretta) nesting at Wassaw Island, Georgia (31.89°N, 80.97°W), between 2004 and 2011 with resulting possible fitness effects. Stable isotope analysis was used to assign the adult female loggerheads to one of three foraging areas in the Northwest Atlantic Ocean. Our data indicate that foraging area preference influences the size, fecundity, and breeding periodicity of adult female loggerhead turtles. We also found that the proportion of turtles originating from each foraging area varied significantly among the years examined. The change in the number of nesting females across the years of the study was not a result of uniform change from all foraging areas. We develop a novel approach to assess differential contributions of various foraging aggregations to changes in abundance of a sea turtle nesting aggregation using stable isotopes. Our approach can provide an improved understanding of the influences on the causes of increasing or decreasing population trends and allow more effective monitoring for these threatened species and other highly migratory species.

Uses, Beliefs, and Conservation of Turtles by Ashaninka Indigenous People, Central Peru

Abstract We used informal conservation and focus group techniques to gather information in 2 Ashaninka communities in Pichis River valley, central Peru. We found that turtles were mainly used as food, although some medicinal and supernatural uses were also reported. Locals demonstrated a comprehensive knowledge on the underlying causes of contemporary reductions in turtle abundance within their territory; their spiritual beliefs, including taboos on catching turtles, and those relating to supernatural or sacred sites caused them to avoid hunting and fishing in some wetlands.

An Assessment of Green Turtle (Chelonia mydas) Stocks Along the Texas Coast, with Emphasis on the Lower Laguna Madre

The in-water status of green turtles (Chelonia mydas) in the northwestern Gulf of Mexico has received comparatively little attention in the management and conservation of this species in US waters. We addressed this void via entanglement netting surveys at 3 estuarine areas (Lavaca-Matagorda Bay, the Aransas Bay complex, and the lower Laguna Madre [LLM]) to assess trends in the relative abundance, distribution, and size composition of green turtles in Texas inshore waters during 1991–2010. Overall catch per unit effort (CPUE) in the LLM (1.5 turtles/km-hr) was significantly higher than that observed in the other 2 estuaries and corresponded to general climate patterns and seagrass areal coverage along the Texas coast. Yearly CPUE of green turtles from the LLM exhibited a significant exponential increase from 1991 to 2010, despite variability in capture rate during recent years. Mean straight carapace length (SCL) of green turtles was statistically similar across the 3 study areas and indicative of dominance by juvenile individuals (LLM mean = 42.2 cm SCL). Historical green turtle size data in the LLM also reveal an overall decreasing trend in mean SCL and shift toward an increased percentage of smaller individuals (30–39.9- and 40–49.9-cm SCL size classes). Also, sighting frequency of postpelagic green turtles at the Brazos-Santiago Pass jetties within the LLM during 2009 was roughly 9 times that reported for comparable months during 1992–1993. These results are indicative of enhanced recruitment of neritic green turtles to the northwestern Gulf of Mexico, most likely due to elevated nesting productivity at beaches in Mexico, Florida, the Caribbean, and the western Atlantic. Overall, the lower Texas coast serves as an important developmental foraging habitat for an increasing population of juvenile green turtles in the northwestern Gulf of Mexico.

Telemetry as a tool for improving estimates of marine turtle abundance

Accurate estimates of abundance are fundamental to the conservation of threatened species, but are often difficult to obtain directly. Population size assessments of marine turtles are often based on counts of nests, which are then related to abundance using the mean number of clutches laid by individuals within a season. Due to low re-encounter probabilities, clutch frequency has proven difficult to estimate reliably, particularly for large populations that make a major contribution to global stock assessments. We use a combination of VHF radio-telemetry and Argos-linked Fastloc™ GPS devices to improve clutch frequency estimates for one of the world’s largest green turtle rookeries at Ascension Island. Females fitted with VHF tags at the start of the season (n=40) were re-encountered with a probability of 85% and laid a minimum average of 5.8 clutches. Three of these turtles were fitted with VHF and GPS devices and using the data collected by the latter, were found to lay an average of 6.3 clutches. GPS-telemetry detected emergences observed using radio-telemetry, and confirmed that some radio-tagged turtles laid again after their last observed emergence. Correcting for missed nesting events yielded a mean clutch frequency of 6.3, more than doubling the previous estimate of 3.0 for this population. Applying this revised assessment to annual nest counts reduces the estimated size of this population by 52%. Conventional tagging approaches may considerably underestimate annual fecundity of turtles, resulting in inflated population size estimates. We call for urgent reassessment of baseline abundance values for regionally important populations.

Ecology and Conservation of Marine Turtles in a Central Pacific Foraging Ground

Abstract Foraging grounds are critical to the survival of marine turtles, yet studies of these areas lag behind those of nesting sites. Our study represents the first data and discussion on marine turtle distribution, abundance, and health at a marine turtle foraging ground in the central Pacific, Palmyra Atoll National Wildlife Refuge, which constitutes a regionally important mixed-size-class foraging ground for green turtles (Chelonia mydas) and, to a lesser extent, for hawksbill turtles (Eretmochelys imbricata). Surveys and anecdotal reports suggest that nesting activity is rare, and we have confirmed the presence of limited suitable nesting habitat. During in-water activities from 2008 to 2011, we caught 211 green turtles ranging from postpelagic juveniles to adults (weight: mean = 44.6 kg, range = 7.2–146.3 kg; curved carapace length (CCL): mean = 69.7 cm, range = 41.0–113.6 cm) and 2 juvenile hawksbills (weight2009 = 16.3 kg, CCL2009 = 57.0; weight2011 = 11.2 kg, CCL2011 = 50.5 cm). ...

Do Ponds on Golf Courses Provide Suitable Habitat for Wetland-Dependent Animals in Suburban Areas? An Assessment of Turtle Abundances

Abstract Golf courses represent a common type of anthropogenically modified habitat in suburban environments. Golf courses may provide suitable habitat for semi-aquatic animals in suburban areas, yet studies comparing animal abundances in golf course ponds with other pond types in suburban environments are somewhat limited. In this study, we compared turtle abundances in golf course ponds with ponds found in residential areas and ponds found in rural (farm) areas and examined the relationship between turtle abundance and residential land-cover within individual golf courses. We captured turtles in 10 golf course ponds, 5 ponds surrounded by residential development, and 5 ponds located on farms. We estimated abundance and the effects of pond area, pond type (i.e., residential, golf, farm) and percentage of residential development within golf course boundaries. Using binomial mixture models and Bayesian inference, we found that ponds surrounded by residential development had lower abundances of Painted Turt...

Effects of the freshwater turtle Trachemys scripta elegans on ecosystem functioning: an approach in experimental ponds

The effect of red-eared sliders (Trachemys scripta elegans) on aquatic ecosystem processes and macroinvertebrate community was investigated in artificial ponds that were stocked with turtles or kept free of them. Compared to ponds without turtles, ponds with turtles displayed significantly higher values of pH, conductivity, sediment accumulation, and leaf litter decomposition rates, as well as a higher abundance of invertebrates, specifically that of the Hemiptera and Ephemeroptera. The biomass of periphyton was not affected by the presence of turtles. These results suggest that the presence of T. s. elegans affects environmental conditions in ponds, and thus potentially ecosystem processes. Reduced abundance or loss of turtles in aquatic systems could therefore result in significant consequences on ecosystem functioning.

Spatial clustering of loggerhead sea turtles in coastal waters of the NW Atlantic Ocean: implications for management surveys

A regional (29.9 to 33.1° N) trawl survey was conducted from 2000 to 2003 and 2008 to 2011 to assess the relative abundance of sea turtles on an important foraging ground. A total of 1461 loggerhead sea turtles Caretta caretta were captured in 23% of 4756 trawling events ran- domly conducted in coastal waters 4 to 17 m deep. Seventy-five percent of positive catches con- sisted of the capture of a single loggerhead sea turtle with up to 10 loggerhead sea turtles cap- tured per event. Loggerhead sea turtle capture locations were significantly clustered throughout the survey area. Nine percent of sampling events (446) occurred in spatial 'hotspots' and captured 23% of loggerhead sea turtles (339). Four percent of sampling events (193) occurred in spatial 'coldspots' and captured 1% of loggerhead sea turtles (18). The probability of loggerhead sea tur- tle capture in any given trawling event was significantly greater following the capture of a logger- head sea turtle in the previous trawling event, but twice as great within hotspots (0.53) as else- where (0.25). Hot- and coldspots were not explained by carapace length, turtle sex, genetic haplotype, 25 biotic and abiotic attributes associated with trawling events, or bycatch co-occur- rence. Because of the universal application of these standardized and relatively easy to compute metrics, we recommend their inclusion in future studies to account for discrepancies in spatial distribution patterns.