Movements of bonnetheads, <Emphasis Type="Italic">Sphyrna tiburo</Emphasis>, as a response to salinity change in a Florida estuary

The movement of bonnetheads, Sphyrna tiburo, within an estuarine system on the Gulf of Mexico coast of Florida was examined to define response to salinity change. Shark presence and movements were evaluated by acoustic monitoring and gillnet sampling. Acoustic monitoring data were used to investigate active selection of different zones within the estuary based on differences in salinity among zones. Sharks were monitored for 187 days in 2003 and 217 days in 2004 in salinities ranging from 11.0 to 31.0 ppt in 2003 and 15.8 to 34.6 ppt in 2004. Monitoring data supported the hypothesis that salinity played a role in the distribution and movement of S. tiburo. Catch per unit effort (CPUE) data obtained from gillnet sampling from 1995 to 2004 were examined to determine affinity or avoidance of specific salinities within the study site as calculated using an electivity index. Electivity analysis showed almost no affinity or avoidance for specific salinity values. The difference in results between the CPUE and acoustic monitoring in relation to the potential effects of salinity likely relate to the nature of the data, with acoustic monitoring providing continuous data and CPUE providing snapshot location data. The results of this study suggest that although S. tiburo are collected within a wide range of salinity levels, salinity may affect movement and distribution. Salinity effects may be more pronounced during periods of prolonged and/or large changes in salinity as detected by long-term monitoring.     

Estimation of Shark Home Ranges using Passive Monitoring Techniques

We examined a population of blacktip sharks, Carcharhinus limbatus, within a coastal nursery area to define how individuals use the nursery habitat throughout the summer. We used a series of acoustic hydrophones to passively monitor the movement patterns of sharks for periods up to 167 days. We used passive monitoring data to calculate home range estimates using minimum convex polygon (MCP) and fixed kernel estimators. MCP calculated the extent of an individual's range. Kernel estimates provided information regarding the utilization of space within the home range including core area (50% kernel) and larger excursions outside the core area (95% kernel). Individuals within the nursery area typically used a consistently small core area. All sharks monitored in the study site underwent a home range expansion during the month of July, suggesting a synchronous population-level change in habitat use. This change in habitat use was reflected in all home range calculations. Passive monitoring revealed that young sharks remain within the nursery area for up to 6 months. The long-term use of this nursery area reflects its critical importance to young blacktip sharks.     

Seasonal and Ontogenetic Changes in Movement Patterns of Sixgill Sharks

Background

Understanding movement patterns is fundamental to population and conservation biology. The way an animal moves through its environment influences the dynamics of local populations and will determine how susceptible it is to natural or anthropogenic perturbations. It is of particular interest to understand the patterns of movement for species which are susceptible to human activities (e.g. fishing), or that exert a large influence on community structure, such as sharks.

Methodology/Principal Findings

We monitored the patterns of movement of 34 sixgill sharks Hexanchus griseus using two large-scale acoustic arrays inside and outside Puget Sound, Washington, USA. Sixgill sharks were residents in Puget Sound for up to at least four years before making large movements out of the estuary. Within Puget Sound, sixgills inhabited sites for several weeks at a time and returned to the same sites annually. Across four years, sixgills had consistent seasonal movements in which they moved to the north from winter to spring and moved to the south from summer to fall. Just prior to leaving Puget Sound, sixgills altered their behavior and moved twice as fast among sites. Nineteen of the thirty-four sixgills were detected leaving Puget Sound for the outer coast. Three of these sharks returned to Puget Sound.

Conclusions/Significance

For most large marine predators, we have a limited understanding of how they move through their environment, and this clouds our ability to successfully manage their populations and their communities. With detailed movement information, such as that being uncovered with acoustic monitoring, we can begin to quantify the spatial and temporal impacts of large predators within the framework of their ecosystems.     

Spatial ecology of juvenile lemon sharks (<Emphasis Type="Italic">Negaprion brevirostris</Emphasis>) in tidal creeks and coastal waters of Eleuthera,The Bahamas

Fisheries exploitation and habitat alteration are threatening lemon shark (Negaprion bevirostris) populations because they use nearshore regions as nursery sites. As such, there is a need for information on the spatial ecology of juvenile lemon sharks to identify critical habitats that require protection, as well as to understand their basic ecology. The purpose of this study was to determine the habitat preferences and movement patterns of juvenile lemon sharks along a sub-section of coastline characterized by coastal flats and tidal creeks of Eleuthera, The Bahamas. Eleven juvenile lemon sharks (766 ± 127 mm total length; mean±SD) were captured from various tidal creeks within the 23 km study area and were surgically implanted with acoustic transmitters. A series of 27 hydrophone receivers acted as a passive monitoring array to detect tagged individuals as they moved among habitats. Findings suggest that juvenile lemon sharks tagged in this study prefer shallow water habitats within tidal creeks, and typically display high site fidelity with occasional forays to alternate habitats or creeks. In fact, more than 90% of tagged lemon sharks had the greatest percentage of detections located at a receiver at or close to the location where they were tagged. There was no evidence of differences in diel or seasonal movement and habitat use. Knowledge gained from this study will be useful for directing future conservation and management strategies including coastal development plans and marine protected areas.     

Residence and movement patterns of cownose rays Rhinoptera bonasus within a south-west Florida estuary

Between July 2003 and November 2004, 21 cownose rays Rhinoptera bonasus were tagged and tracked within Pine Island Sound estuary, Florida, using passive acoustic telemetry. Residence time of individuals ranged between 1 and 102 days. No relationship was detected between ray activity and tidal stage or time of day. Minimum convex polygons (MCP) and kernel utilization distributions (KUD) were calculated over several time frames to demonstrate the extent of an animal's home range and core areas of use. Total MCPs ranged between 0·81 and 71·78 km² (mean = 22·01 km²), with daily MCPs as large as 25·8 km². Total 95% KUDs ranged between 0·18 and 62·44 km² (mean = 22·63 km²), while total 50% KUDs were smaller, ranging from 0·09 to 9·68 km² (mean = 3·33 km²). Both MCP and KUD areas exhibited a positive relationship with residence time and R. bonasus size. As mobile, pelagic swimmers capable of traversing large distances, these data show that cownose rays travel extensively throughout this estuary, yet may remain within very small areas for extended periods.     

First documented occurrences of the shortnose sturgeon (Acipenser brevirostrum,Lesueur, 1818) in the Saco River,Maine, USA

During sampling efforts to study the more abundant Atlantic sturgeon, Acipenser oxyrinchus oxyrinchus, between May of 2009 and November of 2011, four shortnose sturgeon were captured in gill nets near the mouth of the Saco River, Maine. Two of these individuals were tagged with acoustic transmitters to monitor their movement within the Saco River. Additionally, six shortnose sturgeon that had been tagged with acoustic transmitters in the Merrimack River, Massachusetts were detected on the acoustic array deployed within the Saco River and its estuary over this time period. These incidences represent the first verified documentation of shortnose sturgeon within this estuary.     

Scale and pattern of broadnose sevengill shark Notorynchus cepedianus movement in estuarine embayments

The detailed movements of 32 acoustically tagged broadnose sevengill shark Notorynchus cepedianus were documented in and around north-east Pacific Ocean estuarine embayments from 2005 to 2007. Arrangements of passive acoustic receivers allowed analysis of movement at several spatial scales, with sex and size examined as possible factors influencing the pattern and timing of these movements. Notorynchus cepedianus exhibited a distinctly seasonal pattern of estuary use over three consecutive years, entering Willapa Bay in the spring, residing therein for extended periods of time during the summer and dispersing into nearshore coastal habitats and over the continental shelf during the autumn. Notorynchus cepedianus within Willapa Bay showed spatio-temporal patterns of segregation by size and sex, with males and small females using peripheral southern estuary channels early in the season before joining large females, who remained concentrated in central estuary channels for the entire season. Individuals displayed a high degree of fidelity not only to Willapa Bay (63% were documented returning over three consecutive seasons), but also to specific areas within the estuary, showing consistent patterns of site use from year to year. Cross-estuary movement was common during the summer, with most fish also moving into an adjacent estuarine embayment for some extent of time. Most winter and autumn coastal detections of N. cepedianus were made over the continental shelf near Oregon and Washington, U.S.A., but there were also examples of individuals moving into nearshore coastal habitats further south into California, suggesting the feasibility of broad-scale coastal movements to known birthing and nursery grounds for the species. These findings contribute to a better understanding of N. cepedianus movement ecology, which can be used to improve the holistic management of this highly mobile apex predator in regional ecosystems.     

Whale Shark (Rhincodon typus) Seasonal Presence,Residence Time and Habitat Use at Darwin Island,Galapagos Marine Reserve

The life history of the whale shark (Rhincodon typus), including its reproductive ecology, still remains largely unknown. Here, we present results from the first whale shark population study around Darwin Island, Galapagos Marine Reserve. Following a diversified approach we characterized seasonal occurrence, population structure and size, and described habitat use of whale sharks based on fine scale movements around the island. Whale shark presence at Darwin Island was negatively correlated with Sea Surface Temperature (SST), with highest abundance corresponding to a cool season between July and December over six years of monitoring. From 2011 to 2013 we photo-identified 82 whale sharks ranging from 4 to 13.1 m Total Length (TL). Size distribution was bimodal, with a great majority (91.5%) of adult female individuals averaging 11.35 m±0.12 m (TL±SE), all but one showing signs of a potential pregnancy. Population dynamics models for apparently pregnant sharks estimated the presence of 3.76±0.90 (mean ± SE) sharks in the study area per day with an individual residence time of 2.09±0.51 (mean ± SE) days. Movement patterns analysis of four apparently pregnant individuals tracked with acoustic tags at Darwin Island revealed an intense use of Darwin''s Arch, where no feeding or specific behavior has been recorded, together with periodic excursions around the island''s vicinity. Sharks showed a preference for intermediate depths (20–30 m) with occasional dives mostly to mid-water, remaining the majority of their time at water temperatures between 24–25°C. All of our results point to Darwin Island as an important stopover in a migration, possibly with reproductive purposes, rather than an aggregation site. Current studies carried out in this area to investigate regional scale movement patterns may provide essential information about possible pupping grounds for this enigmatic species.     

Diversity in destinations, routes and timing of small adult and sub-adult striped bass Morone saxatilis on their southward autumn migration

Almost three-quarters of the 46 young adult and sub-adult striped bass Morone saxatilis that were acoustically tagged in Plum Island Estuary, Massachusetts, U.S.A., in the summer of 2006 were detected in one or more southern coastal arrays during their autumn migration. On the basis of the trajectories along which these M. saxatilis moved from feeding to overwintering areas, three migratory groups emerged. After leaving Plum Island Estuary, about half of the fish were detected only in a mid-latitude array, Long Island Sound. The other half of the tagged fish were detected during autumn and winter in a more southern array, the Delaware Estuary. This latter group of fish may have used two routes. Some travelled to the Delaware Estuary through Long Island Sound while other fish may have taken a second, more direct, coastal route that did not include Long Island Sound. Consequently, a seemingly homogeneous group of fish tagged at the same time in the same non-natal feeding location exhibited a diversity of southward movement patterns that could affect population-level processes. These three groups that differed in overwintering location and migration route could be movement contingents with migratory connectivity.     

Phylogeography and population genetics of the cryptic bonnethead shark Sphyrna aff. tiburo in Brazil and the Caribbean inferred from mtDNA markers

Resolving the identity, phylogeny and distribution of cryptic species within species complexes is an essential precursor to management. The bonnethead shark, Sphyrna tiburo, is a small coastal shark distributed in the Western Atlantic from North Carolina (U.S.A.) to southern Brazil. Genetic analyses based on mitochondrial markers revealed that bonnethead sharks comprise a species complex with at least two lineages in the Northwestern Atlantic and the Caribbean (S. tiburo and Sphyrna aff. tiburo, respectively). The phylogeographic and phylogenetic analysis of two mitochondrial markers [control region (mtCR) and cytochrome oxidase I (COI)] showed that bonnethead sharks from southeastern Brazil correspond to S. aff. tiburo, extending the distribution of this cryptic species >5000 km. Bonnethead shark populations are only managed in the U.S.A. and in the 2000s were considered to be regionally extinct or collapsed in southeast Brazil. The results indicate that there is significant genetic differentiation between S. aff. tiburo from Brazil and other populations from the Caribbean (Φ_ST = 0.9053, P < 0.000), which means that collapsed populations in the former are unlikely to be replenished from Caribbean immigration. The species identity of bonnethead sharks in the Southwest Atlantic and their relationship to North Atlantic and Caribbean populations still remains unresolved. Taxonomic revision and further sampling are required to reevaluate the status of the bonnethead shark complex through its distribution range.     

Habitat use and spatial segregation of adult spottail sharks Carcharhinus sorrah in tropical nearshore waters

An array of acoustic receivers deployed in Cleveland Bay, north Queensland, Australia, passively tracked 20 adult spottail sharks Carcharhinus sorrah over 2 years (2009-2010) to define patterns in movement and habitat use. Individuals were present in the study site for long periods, ranging from 8 to 408 days (mean = 185). Size and location of home ranges did not vary over time. A high level of segregation occurred among C. sorrah, with individuals using different types of habitat and showing strong attachment to specific regions. The depth of habitat individuals used varied between sexes. Males tended to use a narrow range of habitat depths within the study site (2·8-6·0 m), whereas females used shallower habitats (1·4-6·2 m) and displayed a seasonal shift in the depth of habitat used. Mean monthly habitat depth used varied by as much as 2 m for females, with individuals using shallower habitats during the winter months. Long-term presence and consistent home ranges suggest that Cleveland Bay provides important habitat for C. sorrah. By defining patterns in the use of nearshore habitats for C. sorrah, this study improves the understanding of the movement and habitat use of smaller-bodied coastal sharks and may help provide guidance for the management of their populations.     

Short-term Movements of Juvenile and Neonate Sandbar Sharks, Carcharhinus plumbeus, on their Nursery Grounds in Delaware Bay

We investigated short-term movements of neonate and juvenile sandbar sharks, Carcharhinus plumbeus, on their nursery grounds in Delaware Bay. The majority of sharks tracked limited their movements to water less than 5m deep, remained within 5km of the coastline, and occupied oblong activity spaces along the coast. In addition to site-attached coastal movements observed, several sharks moved entirely across Delaware Bay or spent considerable time in deeper portions of the central bay. Sharks tracked on the New Jersey side of the bay tended to spend more time in deeper water, farther from shore than sharks tracked on the Delaware side. Observation-area curves estimated that optimal tracking time for sandbar sharks in Delaware Bay was 41h. Indices of site attachment showed that movement patterns of tracked sandbar sharks varied from nomadic to home ranging. There was no significant difference in rate of movement for day/night, crepuscular periods, or between juveniles and neonates. In general, young sandbar sharks patrolled the coast and appeared to be site attached to some extent, but were capable of making longer excursions, including movement entirely across Delaware Bay.     

Elevated body temperatures of adult female leopard sharks, Triakis semifasciata, while aggregating in shallow nearshore embayments: Evidence for behavioral thermoregulation?

The leopard shark, Triakis semifasciata, is an abundant nearshore elasmobranch, ranging from Baja California, Mexico to Oregon, USA. Mature female leopard sharks have been observed aggregating in shallow embayments throughout California; however, it is unclear why only females aggregate in these shallow areas. The goal of this study was to determine if mature female leopard sharks selectively occupy the warmest areas of a shallow embayment, if free-ranging leopard sharks' body temperatures are significantly warmer during the day than at night, and to quantify temporal use of these shallow habitats. Visual observations of sharks' fine-scale movements within the shallows of Big Fisherman's Cove Marine Life Refuge (Santa Catalina Island) aggregation site indicated that sharks preferred the warmest areas of the embayment and moved to warmer locations over the course of the day (p < 0.05). Active and passive acoustic tracking, along with archival transponder technology (Vemco: V13, V13-R256, VX32TP-CHAT tags respectively) of 16 sharks caught and tagged within this aggregation were used to monitor core body temperature, swimming depth, and movements. Sharks had significantly higher core body temperatures in the late afternoon (1700 h-2000 h) during the summer, showed increased fidelity to thermal refuges during the day and increased movement away from these refuges at night (χ², p < 0.05). Seasonal variations in warm, shallow water usage were also observed. Elevated core body temperature of mature female leopard sharks using warm shallow embayments will likely augment metabolic and physiological functions such as digestion, somatic growth, and possibly reproduction.     

Space Utilization and Swimming Depth of White Sharks, Carcharodon carcharias, at the South Farallon Islands, Central California

This paper presents information on the movements of white sharks, Carcharodon carcharias, at the South Farallon Islands (SFI), central California. Acoustic telemetry techniques provided preliminary data on the diurnal space utilization, movement patterns and swimming depths of four white sharks, ranging from approximately 3.7 to 4.9m in length. Sharks swam within about 10m of the bottom to depths of approximately 30m, but in deeper water they tended to stray more from the bottom. Activity spaces for time periods tracked ranged from 1.84 to 9.15km². Indications are that an inverse relationship exists between length and activity space. During the time tracked, larger individuals swam within particular areas around the islands whereas smaller individuals did not restrict their movements in the same manner. Values of a site attachment index were inversely related to length for all sharks tracked. The site attachment indices, apparent inverse relationship between total length and activity space and observations on telemetered and other known individuals support a hypothesis that larger sharks possess site fidelity in their search for prey at SFI, within and between years. With the high frequency of predation by white sharks on juvenile northern elephant seals at SFI in the fall, the majority of the sharks' movements are probably related to their search for these pinniped prey. These data provide preliminary evidence that white sharks at SFI may search for prey by swimming in a particular area over a number of days or weeks, traversing the area in a manner which maximizes coverage, and swimming close to the bottom or at a distance far enough from the surface to remain cryptic from prey.     

Residency and movement patterns of adult Port Jackson sharks (Heterodontus portusjacksoni) at a breeding aggregation site

Examining the movement ecology of mesopredators is fundamental to developing an understanding of their biology, ecology and behaviour, as well as the communities and ecosystems they influence. The limited research on the residency and movements of benthic marine mesopredators has primarily used visual tags, which do not allow for the efficient and accurate monitoring of individual space use. In this study, the authors investigated the residency and movement patterns of Port Jackson sharks Heterodontus portusjacksoni (Meyer 1793) at a breeding aggregation site in Jervis Bay, south-eastern Australia, using passive acoustic telemetry to further our understanding of the movement ecology of these important mesopredators. Between 2012 and 2014, individuals were tagged with acoustic transmitters, and their residency and movements within the bay were monitored for up to 4 years. H. portusjacksoni showed strong preferences for particular reefs within and between breeding seasons. Males had significantly higher residency indices at their favoured sites relative to females, suggesting that males may be engaging in territorial behaviour. Conversely, female H. portusjacksoni exhibited higher roaming indices relative to males indicating that females may move between sites to assess males. Finally, H. portusjacksoni showed temporal variation in movements between reefs with individuals typically visiting more reefs at night relative to the day, dusk and dawn corresponding with their nocturnal habits.     

Intraspecific variation in vertical habitat use by tiger sharks (Galeocerdo cuvier) in the western North Atlantic

Tiger sharks (Galeocerdo cuvier) are a wide ranging, potentially keystone predator species that display a variety of horizontal movement patterns, making use of coastal and pelagic waters. Far less, however, is known about their vertical movements and use of the water column. We used pop‐up satellite archival tags with two data sampling rates (high rate and standard rate tags) to investigate the vertical habitat use and diving behavior of tiger sharks tagged on the Puerto Rico–Virgin Islands platform and off Bermuda between 2008 and 2009. Useable data were received from nine of 14 sharks tagged, tracked over a total of 529 days. Sharks spent the majority of their time making yo‐yo dives within the upper 50 m of the water column and considerable time within the upper 5 m of the water column. As a result, sharks typically occupied a narrow daily temperature range (~2°C). Dives to greater than 200 m were common, and all sharks made dives to at least 250 m, with one shark reaching a depth of 828 m. Despite some similarities among individuals, a great deal of intraspecific variability in vertical habit use was observed. Four distinct depth distributions that were not related to tagging location, horizontal movements, sex, or size were detected. In addition, similar depth distributions did not necessitate similar dive patterns among sharks. Recognition of intraspecific variability in habitat use of top predators can be crucial for effective management of these species and for understanding their influence on ecosystem dynamics.     

Seasonal foraging movements and migratory patterns of female Lamna ditropis tagged in Prince William Sound, Alaska

Conventional and electronic tags were used to investigate social segregation, distribution, movements and migrations of salmon sharks Lamna ditropis in Prince William Sound, Alaska. Sixteen salmon sharks were tagged with satellite transmitters and 246 with conventional tags following capture, and were then released in Prince William Sound during summer 1999 to 2001. Most salmon sharks sexed during the study were female (95%), suggesting a high degree of sexual segregation in the region. Salmon sharks congregated at adult Pacific salmon Oncorhynchus spp. migration routes and in bays near Pacific salmon spawning grounds in Prince William Sound during July and August. Adult Pacific salmon were the principal prey in 51 salmon shark stomachs collected during summer months in Prince William Sound, but the fish appeared to be opportunistic predators and consumed sablefish Anoplopoma fimbria, gadids, Pacific herring Clupea pallasi, rockfish Sebastes spp. and squid (Teuthoidea) even when adult Pacific salmon were locally abundant. As Pacific salmon migrations declined in late summer, the salmon sharks dispersed; some continued to forage in Prince William Sound and the Gulf of Alaska into autumn and winter months, while others rapidly moved south‐east thousands of kilometres toward the west coasts of Canada and the U.S. Three movement modes are proposed to explain the movement patterns observed in the Gulf of Alaska and eastern North Pacific Ocean: ‘focal foraging’ movements, ‘foraging dispersals’ and ‘direct migrations’. Patterns of salmon shark movement are possibly explained by spatio‐temporal changes in prey quality and density, an energetic trade‐off between prey availability and water temperature, intra‐specific competition for food and reproductive success. Transmissions from the electronic tags also provided data on depth and water temperatures experienced by the salmon sharks. The fish ranged from the surface to a depth of 668 m, encountered water temperatures from 4·0 to 16·8° C and generally spent the most time above 40 m depth and between 6 and 14° C (60 and 73%, respectively).     

Markov models and network analysis reveal sex‐specific differences in the space‐use of a coastal apex predator

Understanding the links between external variables such as habitat and interactions with conspecifics and animal space‐use is fundamental to developing effective management measures. In the marine realm, automated acoustic tracking has become a widely used method for monitoring the movement of free‐ranging animals, yet researchers generally lack robust methods for analysing the resulting spatial‐usage data. In this study, acoustic tracking data from male and female broadnose sevengill sharks Notorynchus cepedianus, collected in a system of coastal embayments in southeast Tasmania were analyzed to examine sex‐specific differences in the sharks’ coastal space‐use and test novel methods for the analysis of acoustic telemetry data. Sex‐specific space‐use of the broadnose sevengill shark from acoustic telemetry data was analysed in two ways: The recently proposed spatial network analysis of between‐receiver movements was employed to identify sex‐specific space‐use patterns. To include the full breadth of temporal information held in the data, movements between receivers were furthermore considered as transitions between states of a Markov chain, with the resulting transition probability matrix allowing the ranking of the relative importance of different parts of the study area. Both spatial network and Markov chain analysis revealed sex‐specific preferences of different sites within the study area. The identification of priority areas differed for the methods, due to the fact that in contrast to network analysis, our Markov chain approach preserves the chronological sequence of detections and accounts for both residency periods and movements. In addition to adding to our knowledge of the ecology of a globally distributed apex predator, this study presents a promising new step towards condensing the vast amounts of information collected with acoustic tracking technology into straightforward results which are directly applicable to the management and conservation of any species that meet the assumptions of our model.     

Reef-Fidelity and Migration of Tiger Sharks,Galeocerdo cuvier,across the Coral Sea

Knowledge of the habitat use and migration patterns of large sharks is important for assessing the effectiveness of large predator Marine Protected Areas (MPAs), vulnerability to fisheries and environmental influences, and management of shark–human interactions. Here we compare movement, reef-fidelity, and ocean migration for tiger sharks, Galeocerdo cuvier, across the Coral Sea, with an emphasis on New Caledonia. Thirty-three tiger sharks (1.54 to 3.9 m total length) were tagged with passive acoustic transmitters and their localised movements monitored on receiver arrays in New Caledonia, the Chesterfield and Lord Howe Islands in the Coral Sea, and the east coast of Queensland, Australia. Satellite tags were also used to determine habitat use and movements among habitats across the Coral Sea. Sub-adults and one male adult tiger shark displayed year-round residency in the Chesterfields with two females tagged in the Chesterfields and detected on the Great Barrier Reef, Australia, after 591 and 842 days respectively. In coastal barrier reefs, tiger sharks were transient at acoustic arrays and each individual demonstrated a unique pattern of occurrence. From 2009 to 2013, fourteen sharks with satellite and acoustic tags undertook wide-ranging movements up to 1114 km across the Coral Sea with eight detected back on acoustic arrays up to 405 days after being tagged. Tiger sharks dove 1136 m and utilised three-dimensional activity spaces averaged at 2360 km³. The Chesterfield Islands appear to be important habitat for sub-adults and adult male tiger sharks. Management strategies need to consider the wide-ranging movements of large (sub-adult and adult) male and female tiger sharks at the individual level, whereas fidelity to specific coastal reefs may be consistent across groups of individuals. Coastal barrier reef MPAs, however, only afford brief protection for large tiger sharks, therefore determining the importance of other oceanic Coral Sea reefs should be a priority for future research.     

Use of the coastal areas adjacent to the Douro estuary as a nursery area for pouting, Trisopterus luscus Linnaeus, 1758

In the present study, the nursery role of the coastal areas adjacent to the Douro estuary for pouting, Trisopterus luscus Linnaeus, 1758, was analysed. The distribution and abundance patterns, diet and growth of T. luscus were studied based on samples collected on seven occasions from November 2000 to March 2002 using a 12 m otter‐trawl with 18 mm mesh size at 12 sites within the estuary and six sites in the adjacent coastal areas. This species occurred only in the coastal areas adjacent to the estuary and a marked seasonal pattern was reported, which reflected the peak abundance of juveniles that use this area as a nursery ground. No marked relationships were obtained between T. luscus abundance and the environmental variables considered. Nonetheless, the highest densities of pouting were recorded at sites where water temperature was high compared with the other sampling areas. Diet of T. luscus juveniles was mainly composed of crustaceans Decapoda, Mysidacea and Amphipoda. The growth rate determined for T. luscus juveniles off the Portuguese coast was higher than those reported for North European areas, and was similar to those obtained in the eastern Mediterranean.