Food habits of the shortfin mako, Isurus oxyrinchus, off the southwest coast of Portugal

Abstract

The shortfin mako, Isurus oxyrinchus, is caught in the eastern North Atlantic as a regular bycatch of the surface-drift longline fishery, mainly directed towards swordfish, Xiphias gladius. Stomachs of 112 shortfin mako sharks, ranging in size from 64 cm to 290 cm fork length, showed teleosts to be the principal component of the diet, occurring in 87% of the stomachs and accounting for over 90% of the contents by weight. Crustaceans and cephalopods were also relatively important in this species' diet, whereas other elasmobranchs were only present in lower percentages. Meal overlap was observed in half of the sampled sharks. No clear trend of prey size selectivity was found, despite smaller individuals seeming incapable of pursuing larger and faster prey. The retention of small prey was also observed in the diet of all sizes of shark. Seasonality in food habits was in accordance with the current availability of food items. The observed vacuity index of 12% is comparable to foraging ecology studies using gillnetting and appears not to be influenced by baited longline gear. Morphological relationships of the digestive system might add important information to the foraging ecology studies and to ecosystem modelling.

Description of diet of pelagic fish in the southwestern Atlantic, Brazil

“…This may happen during the process of fishing and to the opportunistic behavior of these sharks. The absence of elasmobranchs in the diet of I. oxyrinchus helps to corroborate results obtained by Maia et al (2006). As Pikitch et al (2005) state, this absence may be credited to the low densities such sharks and other ones present in the oceanic environment, when compared to more complex habitats.…”

“…As Pikitch et al (2005) state, this absence may be credited to the low densities such sharks and other ones present in the oceanic environment, when compared to more complex habitats. Other large predators, such as X. gladius, should also be considered as potential prey for I. oxyrinchus (Stillwell & Kohler 1982, Maia et al 2006, but this fact was not observed in this study.…”

“…Following Maia et al (2006), a regular ingestion of crustaceans may be more related to young individuals of this elasmobranch. As seen by the IRI 0.6%, this item may be even less important to individuals of A. superciliosus, in a way to corroborate data obtained by Preti et al (2008), who found such prey in only one stomach.…”

Horizontal and vertical movements of longfin makos (Isurus paucus) tracked with satellitelinked tags in the northwestern Atlantic Ocean

“…These observations are consistent with longline catches of longfin makos in that most captures occur during overnight sets with baits set at depths of 0-220 m below the surface (Dodrill and Gilmore, 1979;Queiroz et al, 2006;Hemida and Capapé, 2008;Bustamante et al, 2009). Satellite tracking results for its congener, the shortfin mako, indicate a similar DVM pattern, but shortfin makos do not appear to have as great a tolerance for depth and cold temperatures.…”

“…The longfin mako is a global oceanic species that inhabits both tropical and subtropical waters (Compagno, 2001) but also ranges into temperate seas (Queiroz et al, 2006;Bustamante et al, 2009;Mucientes et al, 2013). In the western Atlantic Ocean, the longfin mako has been documented in the Gulf Stream off the eastern United States, off Cuba's northern coast, as far south as southern Brazil (Compagno, 2001), and as far north as Georges Bank (Kohler et al, 1998).…”