Reproductive strategy of leafscale gulper shark Centrophorus squamosus and the Portuguese dogfish Centroscymnus coelolepis on the Portuguese continental slope

Abstract

Recent data are presented on leafscale gulper shark Centrophorus squamosus and Portuguese dogfish Centroscymnus coelolepis collected during an extended sampling programme carried out at mainland Portuguese landing ports. Although there are some features common to all deepwater squaliform sharks, the two species have different reproductive strategies: C. squamosus has a lower fecundity and larger total length (L T ) at first maturity than C. coelolepis. Despite the scarcity of pregnant C. squamosus in the samples, the L T at birth was estimated at c. 440 mm. For C. coelolepis the results suggest the existence of a non-annual reproductive cycle with two breeding seasons in each year.

Atlantic Multidecadal Oscillation (AMO) and sea surface temperature in the Bay of Biscay and adjacent regions

“…Birdbeak dogfish were captured with deep-water longlines in the Portuguese continental slope, between September 2008 and May 2009, at depths around 1400 -1450 m. Only females in stage 3 (mature: adult) and stage 6 (mature: extrusion), according to the maturity stage key suggested by Figueiredo et al (2008), were considered for this study; in the former, mature eggs were analysed and in the latter, both the pregnant females and their almost full-term embryos were studied. Total length and total weight were recorded for each fish to the nearest millimetre and centigram, respectively, using an ichthyometer and a precision balance; total weight and diameter were recorded for each egg; total length, total weight and sex were recorded for each embryo.…”

Bycatch and incidental catch of the black scabbardfish (Aphanopus spp.) fishery off the Canary Islands

“…This limitation poses serious problems when appropriate management actions are required (Gordon, 2001), and this is further aggravated by the high vulnerability of elasmobranch populations to fishing. Such vulnerability is, to a great extent, due to their life strategies, such as late attainment of sexual maturity, low fecundity and a strong relationship between the number of young and the spawning stock (Stevens et al, 2000;Figueiredo et al, 2008). Despite their known vulnerability to fishing, elasmobranchs have been increasingly exploited as bycatch or incidental catch in pelagic longline fisheries from the 1960s (Baum et al, 2003).…”

Distribution, reproduction and population structure of three gulper sharks (Centrophorus, Centrophoridae) in south-east Australian waters

“…Previous studies into the biology of deepwater squaloid sharks have mainly focussed on the essentially mid-slope species of Centroscyllium, Centroscymnus, Deania and Etmopterus from the North Atlantic Ocean (Yano 1995;Jakobsdóttir 2001;Clarke et al 2002), Japan (Yano andTanaka 1984, 1988) and New Zealand (Wetherbee 1996), while most studies into the biology of Centrophorus dealt with C. squamosus from the north-west Atlantic, for example Girard and Du Buit (1999), Girard et al (2000), Clarke et al (2001), Bañón et al (2008), Figueiredo et al (2008) and Severino et al (2009). Of the shallower upper-slope species, Bass et al (1976) gave brief details of size at maturity for 'C.…”