The goal of this study was to determine the energetic requirements of juvenile scalloped hammerhead sharks (Sphyrna lewini) in Kaneohe Bay, Oahu, Hawaii using a multidisciplinary approach. A large flume/respirometer (635 1) was constructed to determine the critical swimming speeds (Ucrit )' swimming kinematics (tailbeat frequency, tailbeat amplitude, and stride length), and oxygen consumption rates (V02 ) of juvenile sharks over a range of swimming speeds (U). Swimming kinematics were also compared with unconstrained sharks in a seawater pond. These experiments indicated that tailbeat frequency (TBF) and water temperature could be used as a predictor of U and V02 for free-swimming sharks in the field; however, the flume affected the sharks' swimming kinematics at slow speeds. The flume and pond kinematic comparisons were used to correct for flume effects on sharks' V02. An acoustic tailbeat-sensing transmitter was designed and constructed to quantify activity and energy consumption of free-swimming hammerhead shark pups in Kaneohe Bay. Sharks with transmitters behaved similarly to uninstrumented sharks, but incurred a 28% increase in cost of transport due to increased drag from the transmitters. These data were used to correct for the effects of the transmitter on freeswimming sharks in the field. Sharks tracked in Kaneohe Bay with tailbeat transmitters exhibited increased U during dawn and dusk, while sharks tracked in the warmer summer months had higher activity rates and metabolic rates (MR) than a shark tracked during the winter. Sharks tracked in this study had higher MR than those measured for other species of tropical sharks and, as a result, require higher daily rations. Low and negative growth rates determined from sharks in the Bay and declining catch rates over the season suggest that a large percentage of the pups in Kaneohe Bay may starve as the result of their high metabolic requirements. Although prey do not appear to be li~itingi lack of foraging experience compounded by a high daily metabolic demand may explain why sharks lose weight during summer months. Those pups that survive the winter experience lower MR due to seasonal temperature decline and less competition as the result of high neonatal mortality. / x, 130 leaves, bound : ill. (some col.) ; 29 cm. / Missing page 74.

Three hammerhead sharks (Sphyrna spp.) are currently managed as part of the large coastal shark complex in the United States. Including multiple species in an assessment ignores the different stock dynamics of each individual species within the complex due to different life histories. This study completed individual assessments of scalloped (S. lewini), great (S. mokarran), and smooth (S. zygaena) hammerhead sharks in the U.S. Atlantic Ocean and Gulf of Mexico. Combined data for all three species and unclassified hammerhead sharks were also used to produce a stock assessment of the hammerhead shark complex. Depletions of 83%, 96%, and 91% were estimated for scalloped, great, and smooth hammerhead sharks, respectively, between 1981 and 2005. When modeled as a single stock, the hammerhead shark complex experienced a 90% decline over the same time period. All three stocks, and the complex were overfished (below population size associated with maximum sustainable yield (MSY)), and overfishing (fishing level above that associated with MSY) occurred in 2005. We found that scalloped hammerhead shark population recovery is likely to occur within 10 years if catch remains at or below 2005 levels. Great and smooth hammerhead sharks will likely still be overfished in 30 years unless catches are reduced. It appears that the species composition could be changing in this hammerhead shark complex. The faster-growing scalloped hammerhead sharks are able to withstand fishing pressure better than great or smooth hammerhead sharks. However, it is difficult to target any single large coastal shark species while fishing; hence they are subject to similar fishing pressure. The result is a greater decline in great and smooth hammerhead sharks than experienced by scalloped hammerhead sharks. Therefore, the proportion of scalloped hammerhead sharks increased between 1981 and 2005. Species-specific stock assessments, such as those presented here, allow managers to more closely monitor populations of slower-growing species and reduce the risk of overexploitation of those species. / Master of Science

Sharks are considered top predators in many marine ecosystems, and can play an important role in structuring those communities. As a result, it is necessary to understand the factors that influence their abundance and distribution. This is particularly important as fishery managers develop fishery management plans for sharks that identify areas that serve as essential fish habitat (EFH). This includes nursery habitat where sharks are born and juveniles spend the early part of their life. However, our understanding of shark habitat use in the northeast Florida waters is limited. The goal of this thesis was to characterize the abundance and distribution of sharks in northeast Florida estuaries, and to examine the effect of abiotic and biotic factors affecting shark habitat use. A bottom longline survey conducted from 2009 – 2011 indicated that 11 shark species use the estuarine waters of northeast Florida during summer months. Atlantic sharpnose (Rhizoprionodon terraenovae), blacktip (Carcharhinus limbatus), bonnethead (Sphyrna tiburo), and sandbar sharks (Carcharhinus plumbeus) were the most abundant species and made up 87.1% of the total catch. Month, bottom water temperature, and depth were the most important factors determining the presence and abundance of these species. This study also examined the role of prey abundance in determining the abundance of Atlantic sharpnose sharks. The probability of catching an Atlantic sharpnose shark, and the abundance of Atlantic sharpnose sharks, were most influenced by site. Neither potential prey abundance nor preferred prey abundance were not significant factors effecting Atlantic sharpnose abundance. This may be a result of prey sampling not providing an accurate measure of the true availability of prey resources. Other factors, such as predation risk, may better explain habitat use patterns of Atlantic sharpnose sharks. Continued sampling will give a better understanding of the factors influencing shark habitat use in this area.