Reproductive biology of two deep-water sharks from the British Isles, Centroscymnus coelolepis and Centrophorus squamosus (Chondrichthyes: Squalidae)

Abstract

The reproductive biology of two aplacental viviparous deep sea sharks, Centroscymnus coelolepis and Centrophorus squamosus has been studied from 1735 and 675 specimens respectively, collected with bottom trawls between 600 and 1400 m depth off the west coast of the British Isles. A macroscopic maturity scale indicates that for both species, size at first maturity is greater in females than in males. In Centroscymnus coelolepis, genital maturity occurs at an average length of ∼86 cm for males and ∼102 cm for females. In Centrophorus squamosus, males are mature near 98 cm and females near 124 cm total length (TL). Smallest juveniles of both species are absent from catches: no specimens of Centroscymnus coelolepis shorter than 58 cm, nor specimens of Centrophorus squamosus shorter than 84 cm have been recorded. Ovarian fecundity is higher in Centroscymnus coelolepis than in Centrophorus squamosus. A maternal supply has been demonstrated for Centroscymnus coelolepis. Litter size has been estimated only in C. coelolepis because no pregnant females of Centrophorus squamosus were recovered. A dwarf embryo and a pair of twins have been observed. Segregation by sexual stage of development shows that immatures are generally found at greater depths than adults.

Comparisons of Trawl and Longline Catches of Deepwater Elasmobranchs West and North of Ireland

“…The absence of small specimens of the large squalid sharks from west of Ireland and Britain has been well documented (Clarke et al, 2002a;Girard and DuBuit, 1999 (Fig. 5).…”

“…Studies of the life history parameters of these species suggest that they are slow growing, mature relatively late in life and have low fecundities (Clarke et al, 2001;Clarke et al, 2002aClarke et al, , 2002bGirard and DuBuit, 1999). These characteristics imply that they cannot sustain high levels of fishing pressure.…”

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

“…Maturity criteria were based on indices developed for deepwater sharks by Yano (1995), Girard and Du Buit (1999), Stehmann (2002) and Walker (2005). Outer clasper length (CLO; Compagno 1984) was the distance from the clasper tip to its insertion into the pelvic fin, measured with Vernier callipers to the nearest mm.…”

“…Significant landings of Centrophorus squamosus and C. granulosus are reported from several areas of the northeast Atlantic Ocean (Girard and Du Buit 1999;Clarke et al 2001;Correia and Smith 2003) and, for C. granulosus, from the Mediterranean Sea (Guallart and Vicent 2001). While Centroscymnus spp.…”

“…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.…”