Human-induced Mortality Research Articles

Bottlenose dolphins at the southern extreme of the south-western Atlantic: local population decline?

The management scheme of Marine Protected Areas (MPAs) includes monitoring protocols but such activities are not always carried out. This is the case for Golfo San José, a MPA in northern Patagonia, Argentina. It was created in 1975 for the protection of the southern right whale (Eubalaena australis) breeding grounds. Other components of the system, such as dolphin populations have received little attention. This study is the first attempt to estimate sighting rates, group size and overall abundance of a bottlenose dolphin (Tursiops truncatus) population in Golfo San José and adjacent areas after 30 years. An analysis of the seasonal sighting rates indicates that bottlenose dolphins were present in the study area throughout the year but a decline in group size and abundance and major shift in distribution was detected when compared with previous published reports. The settlement of the MPA failed to secure the persistence of the bottlenose dolphin population within its boundaries. Possible explanations for the detected decline are addressed including increased natural mortality, human induced mortality and disturbance, resources depletion and environmental shift.

Dispersal of male bears into peripheral habitats inferred from mtDNA haplotypes

Crop depredation by brown bears (Ursus arctos) in Hokkaido, Japan, has increased over the past 2 decades. With increased depredation, the number of permits issued and the removal of conflict animals have also increased. We hypothesized that peripheral areas adjacent to agricultural lands represent attractive sink-like habitat because of the association between abundant high-quality anthropogenic food resources and high levels of human-induced mortality by nuisance control. We used an allopatric distribution of mitochondrial DNA (mtDNA) haplotypes in females to distinguish core from peripheral habitat; nuisance control for female bears was 2× greater in the periphery. Using these definitions, we investigated 85 male mtDNA haplotypes recovered from dead bears from eastern Hokkaido (1996–2008) and classified the birthplace for 64. Of these, 14 of 31 born in core were killed in periphery, whereas 5 of 33 born in periphery died in core. In periphery, the largest proportion of males killed occurred during early summer (mating season); for females, the largest proportion was in late summer (period of greatest crop damage). We also documented a significant increase in the number of males killed in the periphery since late 1990s. Timing of mortalities suggested that males were attracted to the periphery for both mating opportunities and by abundant anthropogenic food resources. Because our results suggest a directional flow of males from core to periphery, we suspected (although did not document) a net loss of residents from core. If reproduction was unable to compensate, unregulated control killing could eventually result in a decline in the numbers of males residing in the core. Our findings demonstrate an important application of mtDNA analyses as well as how source–sink dynamics can differentially affect males and females because of varying behavioral traits such as home range size and dispersal characteristics.

Serum Amyloid A (SAA) as a Biomarker of Chronic Infection Due to Boat Strike Trauma in a Free-ranging Florida Manatee (Trichechus manatus latirostris) with Incidental Polycystic Kidneys

Watercraft-related trauma is the predominant cause of human-induced mortality in manatees (Trichechus manatus latirostris), a federal- and state-listed endangered species. Pyothorax (documented in this case report) and other secondary infections are common sequelae of inhalation of water and the open wounds caused by boat propellers. These secondary infections can lead to the demise of the animal weeks to months after the traumatic incident when external wounds have healed. Diagnosis of underlying disease on physical examination during capture and restraint can be difficult. Acute phase proteins, including serum amyloid A, fibrinogen, and albumin can be used to diagnose inflammatory disease in manatees and improve quality of medical care and husbandry. We also provide the first report of polycystic kidneys in Sirenians.

Aerial survey abundance estimates of the loggerhead sea turtle Caretta caretta in the Pelagos Sanctuary, northwestern Mediterranean Sea

Aerial line transect surveys, totalling 16 590 km, were performed in winter and sum- mer 2009 in the Pelagos Sanctuary, NW Mediterranean. A total of 207 loggerhead sea turtles were sighted, with only 9 sightings during the winter. In this season average raw 'surface' density (i.e. animals at or near the surface) was 0.002 turtles km -2 , and on the basis of line-transect analysis, we estimated 237 specimens (CV = 34.33%; 95% CI = 122-461). The summer estimate resulted in 4083 animals at surface (CV = 14.59%; 95% CI = 3061-5466) in the study area, with a density of 0.046 km -2 . Results indicated strong seasonal differences and lower densities than those found in comparable surveys in Spanish Mediterranean waters. Nevertheless, the ecological and oceano- graphic features of the Pelagos Sanctuary, established primarily for the protection of marine mam- mals, render it an important area also for Mediterranean loggerhead sea turtles. The potential for human-induced mortalities of turtles summering in the Pelagos Sanctuary is high. In this context, it is vital to obtain reliable estimates of absolute and relative abundance over time, monitor the sta- tus of loggerhead sea turtles and inform the development of effective conservation actions. This study illustrates the ability of aerial surveys to provide such data in this area.

Predicting potential habitat and population size for reintroduction of the Far Eastern leopards in the Russian Far East

The Far Eastern Leopard ( Panthera pardus orientalis; Schlegel, 1857) is perhaps the world’s most endangered large felid subspecies occurring in a single population of ⩽30 adults, and faces immediate risk of extinction unless additional populations can be established within its historical range in the Russian Far East. We used locations of leopard tracks (and their ungulate prey) collected from snow track surveys from 1997 to 2007 to develop resource selection functions (RSF) to identify potential habitat for reintroduction. We compared models that include prey versus those based on landscape covariates, and also included covariates related to human-induced mortality. To estimate potential population size, we used a habitat-based population estimate based on the ratio of population size and RSF value of occupied range. Far Eastern leopards selected for areas with high ungulate density, lower-elevation Korean pine forests on southwest facing slopes, and in areas far from human activity. Using this RSF model, we identified a total of 10,648 km 2 in eight patches >500 km 2 of potential Far Eastern leopard habitat that could harbor a potential population of 105.3 (57.9–147.2) adults. In combination with the existing population, successful reintroductions could result in a total of 139.2 (76.5–194.6) adult leopards, a 3–4-fold increase in population size. Our habitat models assist the reintroduction planning process by identifying factors that predict presence and potential suitable habitat. Identifying the highest quality, most connected patches, in combination with appropriate selection and training of released animals, is recommended for successfully reintroducing Far Eastern leopards, and potentially other endangered carnivores into the wild.

Influence of harvesting pressure on demographic tactics: implications for wildlife management

Summary 1. Demographic tactics within animal populations are shaped by selective pressures. Exploitation exerts additional pressures so that differing demographic tactics might be expected among populations with differences in levels of exploitation. Yet little has been done so far to assess the possible consequences of exploitation on the demographic tactics of mammals, even though such information could influence the choice of effective management strategies. 2. Compared with similar-sized ungulate species, wild boar Sus scrofa has high reproductive capabilities, which complicates population management. Using a perturbation analysis, we investigated how population growth rates (λ) and critical life-history stages differed between two wild boar populations monitored for several years, one of which was heavily harvested and the other lightly harvested. 3. Asymptotic λ was 1·242 in the lightly hunted population and 1·115 in the heavily hunted population, while the ratio between the elasticity of adult survival and juvenile survival was 2·63 and 1·27, respectively. A comparative analysis including 21 other ungulate species showed that the elasticity ratio in the heavily hunted population was the lowest ever observed. 4. Compared with expected generation times of similar-sized ungulates (more than 6 years), wild boar has a fast life-history speed, especially when facing high hunting pressure. This is well illustrated by our results, where generation times were 3·6 years in the lightly hunted population and only 2·3 years in the heavily hunted population. High human-induced mortality combined with non-limiting food resources accounted for the accelerated life history of the hunted population because of earlier reproduction. 5. Synthesis and applications. For wild boar, we show that when a population is facing a high hunting pressure, increasing the mortality in only one age-class (e.g. adults or juveniles) may not allow managers to limit population growth. We suggest that simulations of management strategies based on context-specific demographic models are useful for selecting interventions for population control. This type of approach allows the assessment of population response to exploitation by considering a range of plausible scenarios, improving the chance of selecting appropriate management actions.

Coupled energy pathways and the resilience of size-structured food webs

Size-based food-web models, which focus on body size rather than species identity, capture the generalist and transient feeding interactions in most marine ecosystems and are well-supported by data. Here, we develop a size-based model that incorporates dynamic interactions between marine benthic (detritus-based) and pelagic (primary producer based) pathways to investigate how the coupling of these pathways affects food web stability and resilience. All model configurations produced stable steady-state size spectra. Resilience was measured by the return speed obtained from local stability analysis. Return times following large perturbations away from steady-state were also measured. Resilience varied nonlinearly with both predator and detrital coupling, and high resilience came from predators (1) feeding entirely in the slow benthic zone or (2) feeding across the two energy pathways, with most food coming from the fast pelagic pathway. When most of the energy flowed through the pelagic pathway, resilience was positively related to turnover rate. When most of the energy flowed through the benthic pathway, resilience was negatively related to turnover rate. Analysis of the effects of large perturbations revealed that resilience for pelagic ecosystems depended on the nature of the perturbation and the degree of benthic–pelagic coupling. Areas with very little or no benthic–pelagic coupling (e.g. deep seas or highly stratified water columns) may return more quickly following pulses of detrital fallout or primary production but could be much less resilient to the effects of human-induced mortality (harvesting).

Understanding Oceanic Migrations with Intrinsic Biogeochemical Markers

Migratory marine vertebrates move annually across remote oceanic water masses crossing international borders. Many anthropogenic threats such as overfishing, bycatch, pollution or global warming put millions of marine migrants at risk especially during their long-distance movements. Therefore, precise knowledge about these migratory movements to understand where and when these animals are more exposed to human impacts is vital for addressing marine conservation issues. Because electronic tracking devices suffer from several constraints, mainly logistical and financial, there is emerging interest in finding appropriate intrinsic markers, such as the chemical composition of inert tissues, to study long-distance migrations and identify wintering sites. Here, using tracked pelagic seabirds and some of their own feathers which were known to be grown at different places and times within the annual cycle, we proved the value of biogeochemical analyses of inert tissue as tracers of marine movements and habitat use. Analyses of feathers grown in summer showed that both stable isotope signatures and element concentrations can signal the origin of breeding birds feeding in distinct water masses. However, only stable isotopes signalled water masses used during winter because elements mainly accumulated during the long breeding period are incorporated into feathers grown in both summer and winter. Our findings shed new light on the simple and effective assignment of marine organisms to distinct oceanic areas, providing new opportunities to study unknown migration patterns of secretive species, including in relation to human-induced mortality on specific populations in the marine environment.

Causes of mortality in stranded Common Dolphin (Delphinus sp.) from New Zealand waters between 1998 and 2008

Post-mortem examinations provide valuable information on sources of mortality for marine mammal populations. However, no published data exist to describe causes of death in the New Zealand population of Common Dolphin (Delphinus sp.). In order to examine the proportion of human and non-human induced mortality affecting this population, necropsies were conducted on 133 individuals that stranded around the New Zealand coastline between 1998 and 2008. Of these, 92.5% (n=123) were found as beach cast carcasses, with just 7.5% (n=10) as live strandings that subsequently died or that were euthanized on humane grounds. The sample included 54 males, 67 females and 12 animals of unknown sex from a range of age classes. Of the individuals for which cause of mortality could be established, 41.2% (n=35) were classified as human induced, with 28.2% (n=24) of carcasses exhibiting evidence of net entanglement. A further 10.6% and 32.9% of mortality was attributable to disease and natural (non-human related) causes, respectively. Few examples of disease were detected, but this may be at least partly a consequence of sampling constraints. Of the carcasses assessed, 68.6% of individuals exhibited some form of parasitism. Parasites identified were typical of the genus and considered to be present in low to moderate burdens. The proportion of beach cast carcasses exhibiting evidence of net entanglement suggests that fisheries-related mortality maybe higher than that previously considered for the New Zealand Common Dolphin population.

The Great Gobi B Strictly Protected Area in Mongolia ‐ refuge or sink for wolves Canis lupus in the Gobi

AbstractThe Mongolian hunting law does not mention the wolf Canis lupus, which is generally interpreted in the way that wolves can be hunted anytime and anywhere, including in protected areas. We investigated whether the Great Gobi B Strictly Protected Area (SPA), a strict nature reserve in southwestern Mongolia, acts as a refuge or a sink for wolves in the Gobi. Our expectations were that wolves in the Gobi 1) have large ranges similar to those in other equally unproductive habitats, 2) experience a high hunting pressure, and 3) have recently become an important export item for cross‐border trade to China. We combined GPS positions of two adult wolves, wolf harvest data and a market survey on wildlife products to address the above questions. Range use of the two collared wolves was huge, but varied widely between the two animals (6,670 km2 for an adult female and 26,619 km2 for an adult male) and over time. Reproductive status and residency status were only known during the initial 8‐months monitoring period of the female. During this ‘resident’ period her range size was 1,275 km2. Both wolves showed a clear preference of mountainous terrain over flat steppe, suggesting that only 21% of the SPA constitute preferred wolf habitat. Annual harvest in the park and its vicinity averaged 1 wolf/265 km2 in 2002/03, 1 wolf/120 km2 in 2003/04 and 1 wolf/310 km2 in 2004/05. However, hunting pressure was unequally distributed and particularly high in the northeastern corner of the park. During the active monitoring period of wolf F1, 35 wolves were killed within her ‘resident’ range, suggesting a high hunting pressure. Most wolves were shot from motorised vehicles, possibly explaining the preference of wolves for mountainous terrain which is inaccessible for vehicles. The market surveys revealed products from ∼2,000 wolves on the two border markets, a huge discrepancy to only 150 CITES permits officially issued annually. Although our data are insufficient to allow a truly quantitative assessment of the impact of human induced mortality on wolf conservation status in the Great Gobi B SPA, it points towards a potentially severe conservation problem requiring further attention.

Implications of uncertainty for Canada’s commercial hunt of harp seals (Pagophilus groenlandicus)

AbstractThe Canadian government's current management procedure for harp seals is described by Fisheries and Oceans Canada as using the Precautionary Approach. Employing a similar underlying population model, we simulated the effects of uncertainty involving bias in estimates of human induced mortality, natural mortality, and pup production estimates as a set of robustness trials. Our results indicated that for the range of annual total allowable catches (TAC) considered and set for Canada’s commercial harp seal hunt (250,000 – 350,000), there were plausible circumstances under which the government's management procedures failed to meet their own conservation objectives. By contrast, a precautionary management regime should be robust to such levels of uncertainty. For some scenarios the current management strategy, although not fully specified, is likely to maintain a high TAC despite a declining population. In particular, once a high TAC has been set, the assessments are unlikely to provide the necessary evidence that the TAC should be reduced until the population is at a low level. Hence there is a substantial risk that the population may be depleted below the ‘minimum’ (N50) and ‘critical’ (N30) population reference points. There is a need for a management procedure based on risk analysis to be fully specified and tested. In the interim, reducing TACs to within limits calculated from a well-established precautionary procedure, such as Potential Biological Removal, would be a step towards more precautionary management.

Causes and spatio-temporal variations of non-natural mortality in the Vulnerable Spanish imperial eagle Aquila adalberti during a recovery period

AbstractThe analysis of 267 records of non-natural mortality of the Spanish imperial eagle Aquila adalberti over a 16-year period (1989-2004) shows an annual rate of 15.1 individuals found dead per year and that electrocution (47.7%) and poisoning (30.7%) were the most frequent causes of mortality. Most cases (91.7%) were of human origin, and of those 92.3% were accidental. Just over half (50.2%) were related to the transmission of electricity and human activity (collisions and electrocution), and 40.7% related to game practices and livestock protection (control of predators). No differences between sexes were found but subadults were electrocuted more frequently than expected whilst adults were poisoned more frequently. In breeding areas poison was the most frequent cause of mortality, whereas electrocution was the most common cause of death in dispersal areas. Poisoning occurred more frequently than expected in the Northern and Southern regions compared to the West-Central region. Electrocution was significantly more frequent in the West-Central region, and less common in the Southern region. The increase in electrocutions over the last few years is associated with previous non-permanent corrections on electricity power lines, whilst the increase in the cases of poisoning appears to be associated with the use of illegal poison in predator control by small game practices and for livestock protection. Permanent corrections in power lines and more research and awareness effort in the small game sector are recommended to reduce human-induced mortality in this Vulnerable species.

Survival probabilities of loggerhead sea turtles (<i>Caretta caretta</i>) estimated from capture-mark-recapture data in the Mediterranean Sea

Survival probabilities of loggerhead sea turtles ( Caretta caretta ) are estimated for the first time in the Mediterranean by analysing 3254 tagging and 134 re-encounter data from this region. Most of these turtles were juveniles found at sea. Re-encounters were live resightings and dead recoveries and data were analysed with Barker’s model, a modified version of the Cormack-Jolly-Seber model which can combine recapture, live resighting and dead recovery data. An annual survival probability of 0.73 (CI 95% = 0.67-0.78; n=3254) was obtained, and should be considered as a conservative estimate due to an unknown, though not negligible, tag loss rate. This study makes a preliminary estimate of the survival probabilities of in-water developmental stages for the Mediterranean population of endangered loggerhead sea turtles and provides the first insights into the magnitude of the suspected human-induced mortality in the region. The model used here for the first time on sea turtles could be used to obtain survival estimates from other data sets with few or no true recaptures but with other types of re-encounter data, which are a common output of tagging programmes involving these wide-ranging animals.

Distribution, abundance, and habitat use of introduced Boa constrictor threatening the native biota of Cozumel Island, Mexico

Species introductions are among the most pervasive types of disturbance, seriously affecting island biota and ecosystem dynamics. The management of introduced generalist species, which may live in a wide range of environmental conditions, can be particularly difficult and is a major challenge for the conservation of native insular species. Boa constrictor was introduced onto Cozumel Island, Mexico, in 1971. The introduction of this generalist predator has affected negatively the native species (many of them endemic to the island) on which the boa feed. It is important to determine temporal variation in boa abundance, the areas of the island in which boas live, and the vegetation types they use in order to develop management strategies to reduce boa pressure on the native biota. We used nocturnal road transect sampling and occasional boa encounters during field work, to estimate boa distribution, abundance and habitat use, taking into account its spatiotemporal patterns on Cozumel Island. This study confirms that Boa constrictor is well established, widespread, and abundant on the island. Our results show that boas are distributed throughout Cozumel, in all vegetation types and geographical regions. Overall, there were 0.11 ± 0.03 boa/10 km road transect. There were no significant spatiotemporal differences in boa activity (time of day) and abundance (monthly, seasonally, by vegetation types or regions of the island). According to the habitat use analysis, there were, however, fewer boas than expected in the subdeciduous tropical forest we sampled and in the central-northern region of the island, which coincide with areas inhabited by humans. There were more boas in areas uninhabited by humans, and there was a tendency towards a greater proportion of dead boas in inhabited areas and live boas in uninhabited areas. Cozumel boas are habitat generalists, which are affected by human induced mortality in inhabited areas. There is a vast area uninhabited by humans, with natural vegetation, on the island where boas have suitable habitats available for their continuous existence on Cozumel. This situation, and the adaptability of the boa, makes the control or eradication of this introduced species a critical conservation challenge.

How to manage human-induced mortality in the Eagle Owl Bubo bubo

The Eagle Owl Bubo bubo, which feeds mainly on rabbits and partridges, has been persecuted widely for causing damage to game interests. Although it is a protected species throughout Europe, there is a noteworthy gap in the scientific literature on the causes of mortality in this top predator. Here, we assess the relative importance and the geographical and temporal variation of human-related causes of death by reviewing 1,576 files of individuals admitted to wildlife rescue centres in Spain, a stronghold for Eagle Owls. The main known cause of death was interaction with powerlines followed by persecution and collisions with game fences and cars. There were within-year variations in the distribution of persecution, electrocution and collisions with game fences. Some man-induced causes of mortality were seen to depend on both the geographical region and the period of the year; moreover, mortality within each region was also year-dependent. Since there are strong socio-economic and ethical components involved, management guidelines are discussed bearing in mind such points of view.

Associations Between The Alaska Steller Sea Lion Decline And Commercial Fisheries

The Steller sea lion (SSL) population in Alaska was listed as threatened under the Endangered Species Act in 1990. At that time, several procedural restrictions were placed on the commercial fisheries of the region in an effort to reduce the potential for human-induced mortality on sea lions. Several years have elapsed since these restrictions were put into place, and questions about their efficacy remain. In an effort to determine whether or not fisheries management measures have helped the SSL population to recover, estimates of the fishing activity of the Bering Sea/Gulf of Alaska commercial fisheries in the vicinity of individual SSL rookeries and SSL population trends at those rookeries were made using data from the National Marine Fisheries Service (NMFS) Fisheries Observer Program and Steller Sea Lion Adult Count Database. Fisheries data from 1976-2000 were analyzed in relation to SSL population counts from 1956-2001 at 32 rookeries from the endangered western stock. Linear regression on the principal components of the fisheries data show that a positive correlation exists between several metrics of historical fishing activity and the SSL population decline. The relationship is less consistent after 1991, supporting a hypothesis that management measures around some of the rookeries have been effective in moderating the localized effects of fishing activity on SSL.

Bilateral Action for Right Whales

In their Policy Forum “North Atlantic right whales in crisis” (22 July, p. [561][1]), S. D. Kraus et al. make clear the plight of the North Atlantic right whale, Eubalaena glacialis , and note that whale deaths from ship strikes and fishing gear entanglements have not been diminishing. Kraus et al. call for changes to U.S. National Oceanic and Atmospheric Administration (NOAA) management policy to put strong and immediate emphasis on reducing human-induced mortality of right whales. The species, though, is not restricted to U.S. waters; it ranges from Florida to the Canadian Maritimes. It is listed as Endangered under both the U.S. Endangered Species Act and the Canadian Species at Risk Act. ![Figure][2] CREDIT: NOAA U.S. and Canadian protection and recovery policies for North Atlantic right whales, administered respectively by NOAA and Fisheries and Oceans Canada (DFO), are not precisely the same. Although the current U.S. and Canadian plans both make reducing mortality due to ship strike and net entrapment a higher priority than reducing habitat degradation, the Canadian plan does not address direct human lethal take ([1][3], [2][4]). Bilaterally agreed-upon management policy is essential for the protection of globally endangered migratory species that cross political boundaries. A precedent was set by the bilateral recovery efforts in aid of the whooping crane. Some level of cooperation between the two countries has been achieved regarding the right whale, but it is insufficient to call only for changes to NOAA management policy when coordinated, bilateral management; regular joint meetings; and cooperative actions are needed. The new U.S. recovery plan calls for bilateral cooperative efforts to maximize protection for right whales. Canadian recovery planning should follow suit and both jurisdictions should work together. 1. 1.[↵][5] National Marine Fisheries Service, Recovery Plan for the Northern Right Whale ( Eubalaena glacialis ) (National Marine Fisheries Service, Silver Spring, MD, 2005). 2. 2.[↵][6] North Atlantic Right Whale Recovery Team, Canadian North Atlantic Right Whale Recovery Plan (Department of Fisheries and Oceans, Ottawa, 2000). # Response {#article-title-2} We agree with Sayles and Green. Migratory transboundary species like the right whale require bilateral efforts at many levels. For example, the U.S. National Marine Fisheries Services' Advanced Notice of Proposed Rulemaking ([1][7]) does require the U.S. government to work with Canada to develop bilateral agreements related to shipping. Further, most co-authors on the Policy Forum have benefited from close working relationships with both researchers and managers within Fisheries and Oceans Canada (DFO). Several breakthroughs in right whale conservation have already been made in Canada, including relocation of the internationally adopted shipping lanes in the Bay of Fundy to reduce ship kills, as well as the official recognition of two Conservation Areas where right whales aggregate. The Bay of Fundy shipping lane changes resulted from efforts by Irving Oil, Transport Canada, DFO, the International Maritime Organization, fishing organizations, whale watching groups, and right whale conservationists. Such multilateral partnerships are especially important in conserving transboundary species. However, we are aware that DFO's ability to really make a difference to right whale conservation is dependent on funding for their initiatives, and support for recovery plan implementation has been limited. We encourage both the Canadian government and nongovernmental organizations to support increased funding for right whale conservation in Canada and welcome additional collaboration with our Canadian colleagues, particularly in the development of bilateral measures to ensure the protection of right whales throughout their range. 1. 1.[↵][8] Department of Commerce, National Oceanic and Atmospheric Administration, 50 CFR Part 224 [040506143-4143-01; I.D. 052504C] RIN 0648-AS36 Endangered Fish and Wildlife; Advance Notice of Proposed Rulemaking (ANPR) for Right Whale Ship Strike Reduction, U.S. Fed. Reg. 69 (No. 105), 30857 (2004). [1]: /lookup/doi/10.1126/science.1111200 [2]: pending:yes [3]: #ref-1 [4]: #ref-2 [5]: #xref-ref-1-1 View reference 1. in text [6]: #xref-ref-2-1 View reference 2. in text [7]: #ref-3 [8]: #xref-ref-3-1 View reference 1. in text

Population differentiation of the Atlantic spotted dolphin (Stenella frontalis) in the western North Atlantic, including the Gulf of Mexico

Information about the genetic population structure of the Atlantic spotted dolphin [Stenella frontalis (G. Cuvier 1829)] in the western North Atlantic would greatly improve conservation and management of this species in USA waters. To this end, mitochondrial control region sequences and five nuclear microsatellite loci were used to test for genetic differentiation of Atlantic spotted dolphins in the western North Atlantic, including the Gulf of Mexico (n=199). Skin tissue samples were collected from 1994–2000. Significant heterozygote deficiencies in three microsatellite loci within samples collected off the eastern USA coast prompted investigation of a possible Wahlund effect, resulting in evidence for previously unsuspected population subdivision in this region. In subsequent analyses including three putative populations, two in the western North Atlantic (n=38, n=85) and one in the Gulf of Mexico (n=76), significant genetic differentiation was detected for both nuclear DNA (RST=0.096, P≤0.0001) and mitochondrial DNA (ΦST=0.215, P≤0.0001), as well as for all pair-wise population comparisons for both markers. This genetic evidence for population differentiation coupled to known biogeographic transition zones at Cape Hatteras, North Carolina and Cape Canaveral, Florida, USA, evidence of female philopatry, and preliminary support for significant genetic differences between previously documented morphotypes of Atlantic spotted dolphins in coastal and offshore waters all indicate that the biology and life history of this species is more complex than previously assumed. Assumptions of large, panmictic populations might not be accurate in other areas where S. frontalis is continuously distributed (e.g., eastern Atlantic), and could have a detrimental effect on long-term viability and maintenance of genetic diversity in this species in regions where incidental human-induced mortality occurs.

Natal origin of loggerhead turtles, Caretta caretta, in the neritic habitat off the Italian coasts, Central Mediterranean

Shallow (neritic) waters close to the Italian coasts (Central Mediterranean Sea) are frequently visited by foraging loggerhead turtles, but the nesting populations which rely on this area have not been determined. To estimate the rookery origins of this feeding cohort, mitochondrial DNA control region sequences were analysed from 106 juvenile loggerhead turtles and compared to those published for key nesting populations in the Atlantic and Mediterranean regions using a Bayesian based stock analysis program. Six distinct haplotypes were detected, of which two have previously been reported from both Mediterranean and Atlantic nesting beaches and one only from Atlantic nesting populations. The remaining three haplotypes could not be assigned to a rookery of origin. Mixed stock analysis indicated that the waters along the Southern Italian coasts are utilised primarily by Mediterranean nesting populations, with approximately 68% of the individuals provided by the genetically homogeneous Greece/South eastern Mediterranean nesting aggregate and 23% by the Turkish management unit. 7% of the loggerhead turtles were assigned to Atlantic stock. Our results suggest that only a small proportion of the Atlantic juveniles which enter the Mediterranean to forage in its pelagic waters utilise also the neritic areas along the Italian coasts. This is consistent with theory of juvenile homing, according to which oceanic stage juveniles preferentially recruit to neritic developmental habitats within their natal region, and implies that the elevated human-induced mortality occurring in this area impacts almost exclusively the smaller and demographically more vulnerable Mediterranean loggerhead turtle stock.

DYNAMICAL AND STATISTICAL MODELS FOR EXPLOITED POPULATIONS†

SummaryHuman activities have indirectly modified the dynamics of many populations, accelerating considerably the natural rate of species extinction and raising strong concerns about biodiversity. In many such cases, the underlying ‘natural’ dynamics of the population has been modified by human‐induced increases in mortality, even if the populations are not exploited or harvested in the strict sense. Both dynamical and statistical models are needed to investigate the consequences of human‐induced mortality on the overall dynamics of a population. This paper reviews existing approaches and the potential of recent developments to help form a conceptual and practical framework for analysing the dynamics of exploited populations. It examines both the simple case of an extra source of mortality instantaneously in time, and the theory involved when both risks compete over a continuous time scale. This basic theory is expanded to structured populations, using matrix population models, with applications to the conservation biology of long‐lived vertebrates. The type and degree of compensation expected and approaches to detect it are reviewed, and ways of handling uncertainty are discussed.