How can the feeding habits of the sand tiger shark influence the success of conservation programs?

Abstract

The feeding habits of the sand tiger shark Carcharias taurus, one of the most threatened sharks of the world, are poorly known. Sand tiger sharks are critically endangered in the South-west Atlantic. Since 2007, the law requires that all individuals caught in recreational fisheries off Argentina must be released. Using data from a north Patagonian recreational fishery (n = 164 stomachs with contents), we analyzed the diet of sand tiger sharks in relation with size, sex, maturity stage and season; assessed prey consumption patterns and hooking location; and estimated diet overlap with fishery landings. Sand tiger sharks consumed mainly teleosts (55.4% of the total prey number, N) and elasmobranchs (41.84% N), and ate more benthic elasmobranchs (batoids and angel sharks) as they become larger. Sharks swallowed prey mostly in one piece (93.7%) and were hooked mainly in internal organs (87.4%, n = 175), causing occlusion and perforation of the esophagus and stomach, and lacerations to the pericardium, heart and liver. Sand tiger sharks fed on the most heavily landed species, overlapping almost completely (490%) with fishery landings. Conservation plans should take into account that releasing hooked sharks could be insufficient to minimize fishing mortality and that competition for food with fisheries is likely to occur.

Targeted Catch‐and‐Release of Prohibited Sharks: Sand Tigers in Coastal Delaware Waters

“…There is a growing body of work demonstrating the negative impacts of recreational angling on Sand Tigers (Dicken et al 2006;Lucifora et al 2009;Kneebone et al 2013), with post-release mortality estimates ranging from 3.8% (Dicken et al 2006) to 28% (Kneebone et al 2013. While likely able to recover from the physiological stress of capture (Kneebone et al 2013), the gulp feeding of Sand Tigers can lead to high rates of internal hooking (87%; Lucifora et al 2009), which often results in both acute trauma (e.g., punctured internal organs) and chronic stress from retained tackle. Additionally, recreational anglers often simply cut their fishing line and leave the terminal tackle in the shark (Bansemer and Bennett 2010), which may lead to infection and subsequent mortality (Borucinkska et al 2002).…”

Mechanical properties of sand tiger sharkCarcharias taurusvertebrae in relation to spinal deformity

“…The conservation status of various populations ranges from 'near threatened' to 'critically endangered', with a global categorization of 'vulnerable' (Pollard and Smith, 2009). Dwindling populations are attributed to overfishing (directed and by-catch) and low reproductive output, with some stocks considered highly susceptible to extinction (Otway et al, 2004;Lucifora et al, 2009). Carcharias taurus attains sexual maturity relatively late in life (males: ~190 cm, 6-7 years; females: ~220 cm, 9-10 years), has a 12 month gestation period, reproduces every other year, and only produces two offspring per litter (Compagno, 2001;Lucifora et al, 2002;Gilmore et al, 2005;Goldman et al, 2006).…”

Reproductive biology of the spotback skate Atlantoraja castelnaui in the south‐west Atlantic Ocean

“…Trophic studies on food interactions on the SACE (Milessi, 2008) and particularly on A. castelnaui (Barbini, 2011; Barbini & Lucifora, 2012) demonstrate consumption of teleosts, elasmobranchs, cephalopods and decapods. Probably, A. castelnaui occupying the higher tropic level of the SACE, being consumed only by the sand tiger shark Carcharias taurus Rafinesque 1810 (Lucifora et al , 2009 a ), G. galeu s (Lucifora et al , 2006) and copper shark Carcharhinus brachyurus (Günther 1870) (Lucifora et al , 2009 b ). These characteristics underlie the high susceptibility of A. castelnaui to fishery pressure and the cascading effects on the communities as result of their decline.…”