Foraging ecology of the early life stages of four sympatric shark species

Abstract

Sharks may have an important role in marine ecosystems in relation to populations of fish and invertebrates at lower trophic levels. Fishery management plans stress the need for an ecosystem approach, but few quantitative studies on the foraging ecology of sharks have been published. Stomach contents and catch data of early life stages of Atlantic sharpnose Rhizoprionodon terraenovae, blacktip Carcharhinus limbatus, finetooth Carcharhinus isodon, and spinner sharks Carcharhinus brevipinna taken from fishery independent surveys in Apalachicola Bay, Florida, USA, were examined to test for overlap in resource use. Young-of-the-year Atlantic sharpnose sharks were found to feed mainly on shrimp, juveniles on sciaenids, and adults on clupeids. Young-of-the-year blacktip sharks were found to feed mainly on sciaenids, whereas juveniles fed on clupeids. The primary prey of young-of-the-year and juvenile finetooth and spinner sharks was clupeids. Eight of 10 prey size-selectivity tests showed neutral selection. Compared to relative prey sizes published for teleost piscivores, Atlantic sharpnose and finetooth sharks consume relatively small-sized prey while blacktip sharks consume relatively large prey. Regardless of maturity state and species, diet overlap was high for species-life stage combinations that are similar in size; however, species-life stages did not show significant habitat overlap. Prey categories shared by similar-sized species may not be limiting, although shark species may have alleviated competition pressure by partitioning the resource of time or space.

Trophic inference in two sympatric sharks, Sphyrna lewini and Carcharhinus falciformis (Elasmobranchii: Carcharhiniformes), based on stable isotope analysis at Malpelo Island, Colombia

“…Our results suggest that Sphyrna lewini and Carcharhinus falciformis co-occur around of Malpelo Island, with resource partitioning, similar to other reports for sympatric species (Bethea et al 2004, Papastamatiou et al 2006, Vaudo and Heithaus 2011. Our results further support the theoretical prediction that the diets of cooccurring species of sharks differ and that sharks with very similar diets do not co-occur (Papastamatiou et al 2006).…”

Abundance and Distribution of Sharks in Northeast Florida Waters and Identification of Potential Nursery Habitat

“…The appearance of older juveniles in late spring and age-0 individuals in early summer (after females give birth) is consistent with the occurrence of Blacktip Sharks in nurseries in both the northwest Atlantic (Castro 1996) and northeast and north-central Gulf of Mexico (Bethea et al 2004;Parsons and Hoffmayer 2007). Also, limited tag-return data suggest that age-0 and juvenile Blacktip Sharks use these estuaries throughout the summer months, before moving offshore in the fall.…”

Freezing behaviour facilitates bioelectric crypsis in cuttlefish faced with predation risk

“…Bonnethead sharks are primarily benthic foragers [20,26,37] and search for food almost exclusively along the bottom, where the experimental array was placed. Juvenile blacktip sharks, on the other hand, are benthopelagic foragers [25,37] and frequently feed at the water surface in captivity.…”

“…Cephalopods, and in particular S. officinalis, present an ideal system for studying non-visual crypsis as they fall prey to a diverse group of predators [14 -20], many of which employ acute, non-visual sensory modalities while foraging [21][22][23][24]. For instance, elasmobranch fishes consume a variety of cryptic prey, including several cephalopod species [15,16,25,26], and can locate prey using their electrosensory system alone [21,22,27]. Therefore, visual camouflage may not afford full protection against these predators and freezing may facilitate non-visual cryptic mechanisms (e.g.…”