Metal concentrations in coastal sharks from The Bahamas with a focus on the Caribbean Reef shark

Over the last century anthropogenic activities have rapidly increased the influx of metals and metalloids entering the marine environment, which can bioaccumulate and biomagnify in marine top consumers. This may elicit sublethal effects on target organisms, having broad implications for human seafood consumers. We provide the first assessment of metal (Cd, Pb, Cr, Mn, Co, Cu, Zn, As, Ag, and THg) and metalloid (As) concentrations in the muscle tissue of coastal sharks from The Bahamas. A total of 36 individual sharks from six species were evaluated, spanning two regions/study areas, with a focus on the Caribbean reef shark (Carcharhinus perezi), and to a lesser extent the tiger shark (Galeocerdo cuvier). This is due their high relative abundance and ecological significance throughout coastal Bahamian and regional ecosystems. Caribbean reef sharks exhibited some of the highest metal concentrations compared to five other species, and peaks in the concentrations of Pb, Cr, Cu were observed as individuals reached sexual maturity. Observations were attributed to foraging on larger, more piscivorous prey, high longevity, as well a potential slowing rate of growth. We observed correlations between some metals, which are challenging to interpret but may be attributed to trophic level and ambient metal conditions. Our results provide the first account of metal concentrations in Bahamian sharks, suggesting individuals exhibit high concentrations which may potentially cause sublethal effects. Finally, these findings underscore the potential toxicity of shark meat and have significant implications for human consumers.

The acoustics and acoustic behavior of the California spiny lobster (Panulirus interruptus)

Numerous animals produce sounds during interactions with potential predators, yet little is known about the acoustics of these sounds, especially in marine environments. California spiny lobsters (Panulirus interruptus) produce pulsatile rasps when interacting with potential predators. They generate sound using frictional structures located at the base of each antenna. This study probes three issues--the effect of body size on signal features, behavioral modification of sound features, and the influence of the ambient environment on the signal. Body size and file length were positively correlated, and larger animals produced lower pulse rate rasps. Ambient noise levels (149.3 dB re 1 microPa) acoustically obscured many rasps (150.4+/-2.0 dB re 1 microPa) at distances from 0.9-1.4 m. Significantly higher numbers of pulses, pulse rate, and rasp duration were produced in rasps generated with two antennae compared to rasps produced with only one antenna. Strong periodic resonances were measured in tank-recorded rasps, whereas field-recorded rasps had little frequency structure. Spiny lobster rasps exhibit flexibility in acoustic signal features, but their propagation is constrained, perhaps beneficially, by the noisy marine environment. Examining the connections between behavior, environment, and acoustics is critical for understanding this fundamental type of animal communication.