Insights into vertebral band pair deposition rate in the juvenile common thresher shark (Alopias vulpinus) in the northeastern Pacific Ocean.

Validation of band pair deposition rates in elasmobranch vertebrae is essential for accurate age estimation using band pair counting techniques. We present a validation study of the vertebral band pair deposition rate for juvenile common thresher sharks Alopias vulpinus in the northeastern Pacific Ocean (NEPO) using tag and recapture with oxytetracycline (OTC) injection. A total of 14 juvenile A.

Variable post-release mortality in common shark species captured in Texas shore-based recreational fisheries.

The practice of catch and release fishing is common among anglers but has been shown to cause unintended mortalities in some species. Current post-release mortality estimates used in coastal shark stock assessments are typically derived from boat-based shark fisheries, which differ from shore-based operations that expose sharks to potentially more stressful environmental and handling conditions. Recreational post-release mortality rates in shore-based fisheries must be quantified to improve stock assessment models and to create guidelines that protect species from overexploitation.

Otolith geochemistry reflects life histories of Pacific bluefin tuna.

Understanding biological and environmental factors that influence movement behaviors and population connectivity of highly migratory fishes is essential for cooperative international management and conservation of exploited populations, like bluefin tuna. Pacific bluefin tuna Thunnus orientalis (PBT) spawn in the western Pacific Ocean and then juveniles disperse to foraging grounds across the North Pacific. Several techniques have been used to characterize the distribution and movement of PBT, but few methods can provide complete records across ontogeny from larvae to adult in individual fish.

Diving into the vertical dimension of elasmobranch movement ecology.

Knowledge of the three-dimensional movement patterns of elasmobranchs is vital to understand their ecological roles and exposure to anthropogenic pressures. To date, comparative studies among species at global scales have mostly focused on horizontal movements. Our study addresses the knowledge gap of vertical movements by compiling the first global synthesis of vertical habitat use by elasmobranchs from data obtained by deployment of 989 biotelemetry tags on 38 elasmobranch species.

Natal origin and age-specific egress of Pacific bluefin tuna from coastal nurseries revealed with geochemical markers.

Geochemical chronologies were constructed from otoliths of adult Pacific bluefin tuna (PBT) to investigate the timing of age-specific egress of juveniles from coastal nurseries in the East China Sea or Sea of Japan to offshore waters of the Pacific Ocean. Element:Ca chronologies were developed for otolith Li, Mg, Mn, Zn, Sr, and Ba, and our assessment focused on the section of the otolith corresponding to the age-0 to age-1 + interval. Next, we applied a common time-series approach to geochemical profiles to identify divergences presumably linked to inshore-offshore migrations.

Capture stress and post-release mortality of blacktip sharks in recreational charter fisheries of the Gulf of Mexico.

Understanding the stress responses of sharks to recreational catch and release fishing has important management and conservation implications. The blacktip shark is a popular recreational species targeted throughout the western, central and eastern Gulf of Mexico (Gulf) yet it is unclear what levels of physiological stress result from catch-release fishing practices with hook and line gear and if the stress levels result in post-release mortality. This study correlates physiological response to stress through blood chemistry analysis and examines post-release behaviour of adult blacktip sharks caught to determine post-release mortality rates.

Natal origin of Pacific bluefin tuna from the California Current Large Marine Ecosystem.

Natal origin of subadult (age-1) Pacific bluefin tuna (PBT, ) from the California Current Large Marine Ecosystem (CCLME) was determined using natural tracers in ear stones (otoliths). Age-0 PBT collected from the two known spawning areas in the western Pacific Ocean (East China Sea, Sea of Japan) were used to establish baseline signatures from otolith cores over 4 years (2014-2017) based on a suite of trace elements (Li, Mg, Mn, Sr, Zn and Ba). Distinct chemical signatures existed in the otolith cores of age-0 PBT collected from the two spawning areas, with overall classification accuracy ranging 73-93% by year.

Elements of time and place: manganese and barium in shark vertebrae reflect age and upwelling histories.

As upper-level predators, sharks are important for maintaining marine food web structure, but populations are threatened by fishery exploitation. Sustainable management of shark populations requires improved understanding of migration patterns and population demographics, which has traditionally been sought through physical and/or electronic tagging studies. The application of natural tags such as elemental variations in mineralized band pairs of elasmobranch vertebrae cartilage could also reveal endogenous and exogenous processes experienced by sharks throughout their life histories.

Effects of sample cleaning and storage on the elemental composition of shark vertebrae.

Rationale: Application of vertebral chemistry in elasmobranchs has the potential to progress our understanding of individual migration patterns and population dynamics. However, the influence of handling artifacts such as sample cleaning and storage on vertebral chemistry is unclear and requires experimental investigation.

Methods: Vertebrae centra from blacktip sharks (Carcharhinus limbatus) were cleaned with bleach (NaOCl) for 5 minutes (min), 1 hour (h) and 24 (h) in a cleaning experiment and stored frozen, in 70% ethanol, and 10% formalin treatments for 20 days in a storage experiment.