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....

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SUMMARYShark cage diving is both popular and controversial, with proponents citing educational value and non-extractive use of natural resources and opponents raising concerns about public safety and ecological impacts. Logbook data collected 2004–2008 from two Oahu (Hawaii) shark cage diving operations were analysed to determine whether such voluntary records provide useful insights into shark ecology or ecotourism impacts. Operators correctly identified common shark species and documented gross seasonal cycles and long-term trends in abundance of Galapagos (Carcharhinus galapagensis), sandbar (Carcharhinus plumbeus) and tiger sharks (Galeorcerdo cuvier). Annual cycles in shark abundance may indicate seasonal migrations, whereas long-term trends suggest gradual exclusion of smaller sandbar sharks from cage diving sites. Numerically dominant (> 98%) Galapagos and sandbar sharks are rarely implicated in attacks on humans. Negligible impact on public safety is supported by other factors such as: (1) remoteness of the sites, (2) conditioning stimuli that are specific to the tour operations and different from inshore recreational stimuli and (3) no increase in shark attacks on the north coast of Oahu since cage diving started. Tracking studies are required to validate logbook data and to determine whether sharks associated with offshore cage diving travel into inshore areas used for in-water recreation.

Carlisle et al. Space Use in Mobile Fishes to a variety of pelagic and reef species with a range of spatial ecologies. We suggest that animals need to be tagged across seasons, years, and ontogenetic stages, in order to fully characterize their spatial ecology, which is fundamental to developing and implementing effective MPAs to conserve the full life history of target species.