BACKGROUND:Global aquatic environments are changing profoundly as a result of human actions; consequently, so too are the ways in which organisms are distributing themselves through space and time. Our ability to predict organism and community responses to these alterations will be dependent on knowledge of animal movements, interactions, and how the physiological and environmental processes underlying them shape species distributions. These patterns and processes ultimately structure aquatic ecosystems and provide the wealth of ecosystem services upon which humans depend. Until recently, the vast size, opacity, and dynamic nature of the aquatic realm have impeded our efforts to understand these ecosystems. With rapid technological advancement over the past several decades, a suite of electronic tracking devices (e.g., acoustic and satellite transmitters) that can remotely monitor animals in these challenging environments are now available. Aquatic telemetry technology is rapidly accelerating our ability to observe animal behavior and distribution and, as a consequence, is fundamentally altering our understanding of the structure and function of global aquatic ecosystems. These advances provide the toolbox to define how future global aquatic management practices must evolve.

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The use of fish aggregating devices (FADs) by purse seine fisheries has come under increasing criticism for its potential deleterious impacts on tuna stocks, for high levels of by‐catch and threats to the biodiversity of tropical pelagic ecosystems. Here, we review the current state of scientific knowledge of this fishing technique and current management strategies. Our intent is to encourage objective discussion of the topic and highlight areas worthy of future research. We show that catching juvenile tuna around FADs does not necessarily result in overfishing of stocks, although more selective fishing techniques would likely help obtain higher yield. Levels of non‐tuna by‐catch are comparable to or less than in other commercial tuna fisheries and are primarily comprised of species that are not considered threatened. Accordingly, to minimize impacts on ecosystem balance, there is merit in considering that all species captured in purse seine fisheries (excluding vulnerable species such as turtles and sharks) should be retained, but the consequences of such a measure should be carefully examined before implementation. The take of vulnerable species could be further reduced by introduction of additional mitigation measures, but their potential benefits would be limited without parallel efforts with other gears. Finally, there is no unequivocal empirical evidence that FADs represent an ‘ecological trap’ that inherently disrupts tuna biology although further research should focus on this issue. We encourage RFMOs to expand and improve their FAD management plans. Under appropriate management regimes, FAD fishing could be an ecologically and economically sensible fishing method.

Identification of nursery habitats and knowledge of the trophic ecology and habitat use of juvenile fishes within these habitats are fundamental in developing sound management and conservation strategies. The brown stingray Dasyatis lata is a large benthic predator that inhabits the coastal waters of Hawai'i. Although abundant in these ecosystems, little is known about its basic ecology. Stomach content, bulk and amino acid stable isotope analyses were used to assess diet and habitat use of juvenile brown stingrays and to examine the possibility of competitive interactions with juvenile scalloped hammerhead sharks Sphyrna lewini that are sympatric with brown stingrays in Kāne'ohe Bay, Oahu. Based on stomach contents, brown stingrays fed almost exclusively on crustaceans. An ontogenetic shift in stingray diet and an increase in relative trophic position (TP) were apparent from stomach content and stable isotope analysis. Stingray bulk δ 13 C and δ 15N values indicated long-term foraging fidelity to subregions of the bay. Use of Kāne'ohe Bay as a nursery habitat was supported by nitrogen isotopic analysis of individual amino acids from stingray muscle samples. Our results clearly demonstrated that stingrays foraged within the bay for the majority of their juvenile lives then shifted to offshore habitats with the onset of sexual maturity. Trophic enrichment factors used to estimate TPs from amino acid analysis in previous studies may underestimate TPs in elasmobranchs owing to urea retention for osmoregulation. Potential prey resources were partitioned between stingrays and juvenile scalloped hammerhead sharks, and TP estimates from each analytical method indicated that juvenile scalloped hammerhead sharks forage on higher TP prey than do juvenile brown stingrays. These results show that the study of foraging ecology and habitat use of marine animals can greatly benefit from integrating traditional stomach content and bulk stable isotopic analyses with nitrogen isotopic analyses of individual amino acids. KEY WORDS: Elasmobranch · Amino acids · Trophic position · Ontogenetic shift · Resource partitioning Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 433: [221][222][223][224][225][226][227][228][229][230][231][232][233][234][235][236] 2011 Cortés 2002), identification of nursery habitats and knowledge of the trophic ecology and habitat use of juvenile fishes within these habitats are fundamental in developing sound management and conservation strategies.The trophic ecology of elasmobranchs has traditionally been studied through stomach content analysis (SCA) (Hyslop 1980). However, bulk tissue stable isotope analysis (SIA) has increasingly been used to compliment SCA (e.g. Graham et al. 2007). Stable isotope analysis is based on the observation that the ratio of carbon isotopes ( . Thus, stable isotope analyses provide a complementary method to SCA for detecting ontogenetic shifts in diet and foraging habitat and calculation of TP (Post 2002, Fisk et al....

Nursery habitat use and growth rates of juvenile scalloped hammerhead sharks Sphyrna lewini were measured in a Hawai'i nursery (Kā ne'ohe Bay, Ō 'ahu) using a 28 mo tag-andrecapture study augmented by experimental determination of the relative age of neonate sharks. An estimated 7700 (± 2240 SD) hammerhead sharks are born in Kā ne'ohe Bay each year. Neonates are born in the summer between May and September and had low retention (from 0.07 to 0.15, as a fraction of neonate population size) within the bay from Age 0 to Age 1. A primary cause of low retention appears to be mortality from starvation. Most juvenile sharks recaptured after short periods of time at liberty (< 60 d) showed weight loss. There was also a significant negative relationship between shark weight and umbilical wound condition. Sharks with healed wounds had lower average body weights than sharks with open wounds, indicating that many sharks lose weight in the first few weeks after birth. Shark condition factor (body weight × length -3 ) was also significantly lower during late summer and early fall. Despite this apparent lack of foraging success, growth rates and size distribution of recaptured sharks indicated that juvenile S. lewini utilize Kā ne'ohe Bay for up to 1 yr. During their residency, sharks move throughout the nursery and there is no discernible ontogenetic shift in habitat use. These findings confirmed recent hypotheses that Kā ne'ohe Bay may be more important in providing protection from predators than in providing a plentiful source of food for juvenile S. lewini.KEY WORDS: Tag-recapture · Mark-recapture · Umbilical wound · Philopatry · Growth rate Resale or republication not permitted without written consent of the publisher

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Abstract. Animals are often faced with complex movement decisions, particularly those that involve long-distance dispersal. Partial migrations, ubiquitous among all groups of vertebrates, are a form of long-distance movement that occurs when only some of the animals in a population migrate. The decision to migrate or to be a resident can be dependent on many factors, but these factors are rarely quantified in fishes, particularly top predators, even though partial migrations may have important implications for ecosystem dynamics and conservation. We utilized passive acoustic telemetry, with a Brownian bridge movement model and generalized additive mixed models, to explore the factors regulating partial migration in a large marine predator, the tiger shark, throughout the Hawaiian Islands. Although sharks tended to utilize a particular ''core'' island, they also demonstrated inter-island movements, particularly mature females that would swim from the northwestern Hawaiian Islands to the main Hawaiian Islands (MHI). Immigration to another island was a function of season, sea surface temperature (SST), and chlorophyll a concentration. Our results predict that 25% of mature females moved from remote French Frigate Shoals atoll to the MHI during late summer/early fall, potentially to give birth. Females with core home ranges within the MHI showed limited movements to the NWHI, and immigration to an island was better explained by SST and chlorophyll a concentration, suggesting a foraging function. Dispersal patterns in tiger sharks are complex but can be considered a mix of skipped-breeding partial migration by mature females and individual-based inter-island movements potentially linked to foraging. Therefore, sharks appear to use a conditional strategy based on fixed intrinsic and flexible extrinsic states. The application of Brownian bridge movement models to electronic presence/ absence data provides a new technique for assessing the influence of habitat and environmental conditions on patterns of movement for fish populations.

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