On the diet and reproduction of the oilfishRuvettus pretiosus(Perciformes: Gempylidae) in the eastern Mediterranean

Abstract

The oilfish,Ruvettus pretiosus, is an incidental by-catch of the drifting surface longlines targeting swordfish and Thunnidae in the Mediterranean and elsewhere. Despite its global distribution and frequent occurrence in the catch of many fishing gears, little is known about its biology. In this study we examined the dietary preferences and reproductive biology of this species from specimens caught in the eastern Mediterranean. The most numerous and frequently occurring prey items were benthopelagic fish, followed by cephalopods. The sex-ratio was highly skewed in favour of females (1:8.4), while histological examination of the collected ovaries displayed six developmental stages (perinucleolar, early and late lipid stage; early, middle and late vitellogenesis). Oocyte diameter ranged from 23–69 μm at the perinucleolar stage to 224–366 μm at the late vitellogenesis stage. Spawning is expected to occur during mid and late summer; however there were no individuals available from this period. The findings are discussed in relation to the ecology of the species.

Length-length and length-weight relationships of oilfish (Ruvettus pretiosus), escolar (Lepidocybium flavobrunneum), snake mackerel (Gempylus serpens), and longnose lancetfish (Alepisaurus ferox) from the Gulf of Mexico and the western North Atlantic Ocea

“…No information on the spawning season exists for escolar and snake mackerel. GSIs in the present study compared with the season were consistent with spawning in mid‐ to late summer for oilfish (Vasilakopolous et al., ) and longnose lancetfish spawning year‐round (Nakamura and Parin, ). GSI data in the present study suggested that snake mackerel also spawn year‐round.…”

New Fisheries-related data from the Mediterranean Sea (April 2015)

“…The oilfish Ruvettus pretiosus (Cocco, 1829) is a cosmopolitan benthopelagic fish (Froese & Pauly, 2014). In the Mediterranean, it is an incidental low-value bycatch of surface and demersal longlines (Vasilakopoulos et al, 2011). Previous studies of the species' biology have focused on its diet, reproduction and morphometrics (e.g.…”

“…Previous studies of the species' biology have focused on its diet, reproduction and morphometrics (e.g. Vasilakopoulos et al, 2011). No information on species' growth is available in the relevant literature, or in FishBase (Froese & Pauly, 2014).…”

Fatal predation of oilfish, Ruvettus pretiosus (Gempylidae), by a young short-finned pilot whale, Globicephala macrorhynchus (Delphinidae)

“…For example, the oilfish Ruvettus pretiosus Cocco (1833) and the short-finned pilot whale Globicephala macrorhynchus Gray (1846) occur together and use the same resources: they both prey on squid and fish (Overholtz & Waring, 1991;Vasilakopoulos, Pavlidis & Tserpes, 2011). The oilfish is mesopelagic; it ranges between 100 and 800m deep, but it is more common not deeper than 400m (Nakamura & Parin, 1993).…”