Why aquatic scientists should use sulfur stable isotope ratios (ẟS) more often.

Over the last few decades, measurements of light stable isotope ratios have been increasingly used to answer questions across physiology, biology, ecology, and archaeology. The vast majority analyse carbon (δC) and nitrogen (δN) stable isotopes as the 'default' isotopes, omitting sulfur (δS) due to time, cost, or perceived lack of benefits and instrumentation capabilities. Using just carbon and nitrogen isotopic ratios can produce results that are inconclusive, uncertain, or in the worst cases, even misleading, especially for scientists that are new to the use and interpretation of stable isotope data.

Feeding behavior of yellowfin tuna around two insular regions of the western Atlantic Ocean.

The yellowfin tuna is a very abundant tropical tuna species in the western equatorial Atlantic Ocean and an important fishery resource for the Brazilian tuna fleet. In this study we performed stable isotope analysis to better understand the spatial trophodynamics and dietary changes in yellowfin tuna around two insular marine protected areas in Brazil. A total of 65 yellowfin tuna specimens measuring between 47 and 138 cm LT (total length) were sampled around the archipelagos of Fernando de Noronha (FNA; n = 34) and Saint Peter and Saint Paul (SPSPA; n = 31) between July 2018 and September 2019.

Bull Shark () Occurrence along Beaches of South-Eastern Australia: Understanding Where, When and Why.

Unprovoked shark bites have increased over the last three decades, yet they are still relatively rare. Bull sharks are globally distributed throughout rivers, estuaries, nearshore areas and continental shelf waters, and are capable of making long distance movements between tropical and temperate regions. As this species is implicated in shark bites throughout their range, knowledge of the environmental drivers of bull shark movements are important for better predicting the likelihood of their occurrence at ocean beaches and potentially assist in reducing shark bites.

Ontogenetic changes in the tooth morphology of bull sharks (Carcharhinus leucas).

Teeth are an integral component of feeding ecology, with a clear link between tooth morphology and diet, as without suitable dentition prey cannot be captured nor broken down for consumption. Bull sharks, Carcharhinus leucas, undergo an ontogenetic niche shift from freshwater to marine habitats, which raises the question: does tooth morphology change with ontogeny? Tooth shape, surface area and thickness were measured using both morphometrics and elliptic Fourier analysis to determine if morphology varied with position in the jaw and if there was an ontogenetic change concordant with this niche shift. Significant ontogenetic differences in tooth morphology as a function of position in the jaw and shark total length were found, with upper and lower jaws of bull sharks presenting two different tooth morphologies.

Forecasting intraspecific changes in distribution of a wide-ranging marine predator under climate change.

Globally, marine animal distributions are shifting in response to a changing climate. These shifts are usually considered at the species level, but individuals are likely to differ in how they respond to the changing conditions. Here, we investigate how movement behaviour and, therefore, redistribution, would differ by sex and maturation class in a wide-ranging marine predator.

Metabolic and nutritional condition of juvenile tiger sharks exposed to regional differences in coastal urbanization.

How varying levels of human activity, such as proximity and size of the nearest market (i.e., market gravity), influence the nutritional ecology and physiological condition of highly migratory marine predators is poorly understood.

Negative metal bioaccumulation impacts on systemic shark health and homeostatic balance.

Contamination by metals is among the most pervasive anthropogenic threats to the environment. Despite the ecological importance of marine apex predators, the potential negative impacts of metal bioaccumulation and biomagnification on the health of higher trophic level species remains unclear. To date, most toxicology studies in sharks have focused on measuring metal concentrations in muscle tissues associating human consumption and food safety, without further investigating potential impacts on shark health.

Overcoming multi-year impacts of maternal isotope signatures using multi-tracers and fast turnover tissues in juvenile sharks.

Stable isotopes are often used to determine the ecological role of different age classes of animals, but particularly for young animals this approach may be compromised. During gestation and or incubation body tissues of the young are derived directly from the mother. In neonates or post hatching, there is a period of transformation as the young grow and forage independently, but during this period different organs will continue to reflect the maternal isotopic signature as a function of their turnover rate.

Physiological Impairment as a Result of Bile Accumulation in an Apex Predator, the Tiger Shark ( Péron & Lesueur, 1822).

Physiological adaptations have evolved to help sharks face rapid periods of feast. Tiger sharks are generalist apex predators that rely on a high-lipid/protein diet. To achieve a satisfactory nutritional condition, proper lipid absorption and hepatic storage are needed.

Thermal Imaging Reveals Changes in Body Surface Temperatures of Blacktip Sharks (Carcharhinus limbatus) during Air Exposure.

Fish physiology is significantly affected by temperature variability. During fisheries interactions, fish are often exposed to air and subjected to rapid temperature changes. Fish thermal dynamics during such exposure, and the possible outcomes to their physiology, depend on how heat is distributed across their bodies, the speed at which their body temperatures change, and the size of the individual.

Cookie-cutter shark Isistius spp. predation upon different tuna species from the south-western Atlantic Ocean.

The predation of cookie-cutter sharks Isistius spp. upon the early life stages of yellowfin tuna Thunnus albacares, skipjack tuna Katsuwonus pelamis and little tunny Euthynnus alletteratus are described. New evidence suggesting a connection between commercial fishing and predation by Isistius sp.