Feeding habits of Mustelus henlei on the western coast of Baja California Sur, México

Abstract

Resumen.-El tiburón musola parda Mustelus henlei forma parte de una importante pesquería comercial en la costa occidental de Baja California Sur, México. Sin embargo, se han realizado muy pocos trabajos sobre biología, reproducción y alimentación de esta especie. Nuestro estudio, es el primer trabajo que se realiza en esta especie en la plataforma continental (14 m a 250 m de profundidad) de B.C.S. Mediante un análisis taxonómico, se identificaron un total de 24 tipos de presas, de los cuales 15 fueron crustáceos, 6 peces y 3 cefalópodos. De acuerdo al índice de importancia relativa (IIR) la presa principal fue la langostilla Pleuroncodes planipes (81,4%), seguida de la materia orgánica no identificada (MONI) (15,7%), la macarela Scomber japonicus (0,94%) y los restos de peces (0,84%). En el análisis de importancia de presas por sexos, se encontró que tanto en hembras como en machos, la langostilla P. planipens fue la presa más importante, después MONI y S. japonicus. Las especies importantes en la dieta del tiburón que se encontraron en zonas más profundas (120 a 150 m) a bordo del crucero BIP XII, fueron similares a las encontradas en la localidad más somera (14-40 m) de Punta Lobos, siendo la presa dominante la langostilla y también el MONI. De acuerdo al Índice de Levin M. henlei es considerado un tiburón especialista. Se observó una superposición de dieta por sexo, área y talla. Con el análisis SIMPER se muestró una baja similitud entre las dietas, con valor de significancia reducida entre sexos, tallas y áreas. De acuerdo a la prueba ANOSIM no se encontraron diferencias significativas. El conocer que M. henlei presenta un comportamiento especialista puede ayudar no sólo a la conservación de la especie, sino de su hábitat y de los organismos que se encuentran en él y que son de vital importancia para el tiburón.Palabras clave: Contenido estomacal, superposición de dieta, especialista, Punta Lobos, Baja California Sur, MéxicoAbstract.-The Brown smooth-hound Mustelus henlei is part of an important commercial fishery on the western coast of Baja California Sur (BCS), Mexico. However, very few studies have been performed on the feeding and reproduction biology of these sharks in Mexico. Our study is the first work focusing on this species on the western shelf (14 m to 250 m in depth) of B.C.S. We identified a total of 24 types of prey contents in the stomachs of M. henlei: 15 crustaceans, 6 fish, and 3 cephalopods. According to the index of relative importance (IRI) the main prey items for M. henlei was the pelagic red crab Pleuroncodes planipes (81.4%), followed by unidentified organic material (UOM) (15.7%), the mackerel Scomber japonicus (0.94%), and fish remains (0.84%). Conducting a prey analysis considering sex of M. henlei, P. planipes was the most important prey in both females and males, followed by UOM, and S. japonicus. Sharks found in deeper areas (120-150 m) and those caught on board the exploration ship BIP XII had a similar dietary composition to those found in the shallow waters of Punta Lobos (...

Ontogenetic morphometry of the brown smoothhound sharkMustelus henleiwith implications for ecology and evolution

“…Due to the energetic requirements of migration (Lawson et al, 2019; Del Raye et al, 2013), and the increased predation pressure that often results (Heithaus, 2007; Heupel et al, 2007), it is unlikely that M. henlei juveniles exhibit migratory behaviour. Rather, juveniles may be subject to greater predation pressure than adults, or may travel greater distances during foraging—which may be focussed upon relatively fast‐moving prey such as teleosts (Pantoja‐Echevarría et al, 2020; Rodríguez‐Romero et al, 2013). It is also possible that the vertical movements associated with foraging behaviour which have been reported in this taxon (Rodríguez‐Romero et al, 2013) are performed only by, or more frequently by juveniles.…”

“…Rather, juveniles may be subject to greater predation pressure than adults, or may travel greater distances during foraging—which may be focussed upon relatively fast‐moving prey such as teleosts (Pantoja‐Echevarría et al, 2020; Rodríguez‐Romero et al, 2013). It is also possible that the vertical movements associated with foraging behaviour which have been reported in this taxon (Rodríguez‐Romero et al, 2013) are performed only by, or more frequently by juveniles.…”

“…Suggestions of trophic specialisation are based primarily upon the dominance of certain prey types in the stomach contents of M. henlei individuals (Rodríguez‐Romero et al, 2013), however, this is not inconsistent with seasonal variation in prey availability, which may simply obscure a more opportunist ecology as recovered by other studies (Espinoza et al, 2012). There is also apparent disagreement over whether this species exhibits ontogenetic shifts in trophic ecology (Amariles et al, 2017; Pantoja‐Echevarría et al, 2020; Rodríguez‐Romero et al, 2013). Given the methodological differences between these studies, it is not possible to determine whether these conflicting results represent mere artefacts, or true ecological differences arising due to local adaptation.…”

“…M. henlei is considered by some to be a specialist predator (Goñi Godoy, 2017; Rodríguez‐Romero et al, 2013), while others suggest a generalist or opportunist (Espinoza et al, 2012). Suggestions of trophic specialisation are based primarily upon the dominance of certain prey types in the stomach contents of M. henlei individuals (Rodríguez‐Romero et al, 2013), however, this is not inconsistent with seasonal variation in prey availability, which may simply obscure a more opportunist ecology as recovered by other studies (Espinoza et al, 2012). There is also apparent disagreement over whether this species exhibits ontogenetic shifts in trophic ecology (Amariles et al, 2017; Pantoja‐Echevarría et al, 2020; Rodríguez‐Romero et al, 2013).…”

“…upon relatively fast-moving prey such as teleosts(Pantoja-Echevarría et al, 2020;Rodríguez-Romero et al, 2013). It is also possible thatF I G U R E 4 Linear regression plots from the female-only data set of lateral span-'LS' (a), posterior span-'PS' (b), caudal keel diameter-'KC' (c), dorsal fin length-'DL' (d), dorsal fin height-'DH' (e), lower caudal lobe-'LL' (f) and upper caudal lobe-'UL' (g) against precaudal length-PL.…”