Large-scale distribution of three deep-water squaloid sharks: Integrating data on sex, maturity and environment

Abstract

Deep-water sharks exhibit species-specific reproductive strategies, which include segregation by sex, size and reproductive stage. However, due to the wide spatial distribution of most species, available information, usually collected at a regional scale, is usually not adequate to infer species reproductive spatial dynamics. This study draws together information on the distribution of reproductive stages of three species of squaliform sharks: Portuguese dogfish Centroscymnus coelolepis (Somniosidae), leafscale gulper shark Centrophorus squamosus (Centrophoridae) and birdbeak dogfish Deania calcea (Centrophoridae), gathering data from several geographical areas from the Atlantic, Indian and Pacific Oceans. For each species we analysed the sex ratio and the spatial patterns of reproductive stages within regions, considering the influence of geographical area, depth, season, temperature and Please note that this is an author-produced PDF of an article accepted for publication following peer review. The definitive publisher-authenticated version is available on the publisher Web site 2 salinity. The combination of statistical methods used in this study successfully identified a number of life history patterns which reflect different use of habitats by sex and life cycle stage. Pregnant females of the three species are spatially segregated, inhabiting shallower and/or warmer waters. In the case of the leafscale gulper shark this segregation might be associated with large scale migrations. In contrast, in Portuguese dogfish all adult maturity stages occur in the same geographical area. Pregnant female birdbeak dogfish were rare in all samples. Larger immature specimens of all the three species distribute deeper than the remaining maturity stages in most of the regions analysed. Mature males of leafscale gulper shark and birdbeak dogfish were more broadly distributed than mature females, supporting the possibility of sex-biased dispersal. Neonates and small sized specimens were scarce in the Northeast Atlantic potentially explained by their concentration in nurseries, and/or by gear selectivity. Management measures will benefit from considering the geographic scale of demographic variation between species. However, standardized collaborative approaches will be needed for comprehensive assessment.

First description of deep-water elasmobranch assemblages in the Exuma Sound, The Bahamas

“…(Castro, 2011;Compagno, 1984;McLaughlin and Morrissey, 2004;Russell et al, 1988). Capture depths for S. cubensis ranged from 472.6 m -730.6 m, far greater than the 60 m -380 m previously reported by Compagno (1984), the slightly increased range of 110 m -500 m reported by Castro (2011) or the 50 m to 459 m reported by Jones et al (2014). This variation in depth association is Expanded depth ranges were also found for H. nakamurai, a species thought to inhabit the deep continental slope and have a circumglobal distribution .…”

“…complex and H. nakamurai were the significantly skewed sex ratios. Demographic segregation is considered normal for many populations of shallow water elasmobranchs (Mucientes et al, 2009;Springer, 1967;Speed et al, 2012), and has also been reported in many deep-water species (Girard and Du Buit, 1999;Moura et al, 2014 Squalus cubensis has previously been reported to form large schools stratified by size and sex (Castro, 2011), and it is interesting to note that Daly-Engel et al (2010) reported strong sexual segregation in a congener, Squalus cf. mitsukurii.…”

Reproductive biology and feeding habits of the prickly dogfishOxynotus bruniensis

“…), and one small individual of 33·0 cm L T was recorded in this study on Chatham Rise, suggesting O. bruniensis may pup in multiple locations around New Zealand. Immature individuals have been previously reported at depths deeper than adults (Moura et al, ), however, in the case of O. bruniensis, any small individuals would still occur within the range of commercial and research trawls, and should have been detected. The presence of young O. centrina specimens in coastal waters suggests inshore mating and pupping areas (Capapé et al, ).…”

Annotated checklist of the living sharks, batoids and chimaeras (Chondrichthyes) of the world, with a focus on biogeographical diversity

“…McCulloch 1915 Daley et al (2002), but four of the 2711 specimens reported by Moura et al (2014) were longer (1260, 1360, 1420 and 1620 mm; all females) and among 420 specimens examined by Rochowski et al (2015), the largest female was 1530 mm 376 Deania hystricosa (Garman 1906 Bigelow & Schroeder (1948). Maximum sizes of 315 mm precaudal length (Longley & Hildebrand, 1941) and 500 mm L T (Compagno, 1984a) probably refer to the subsequently described and very similar E. robinsi, which attains a greater maximum size according to Schofield & Burgess (1997).…”