Distribution and reproduction of two deep-sea sharks, Centrophorus squamosus and Centroscymnus coelolepis, exploited in the North-East Atlantic

Authors
Citation
M. Girard, Distribution and reproduction of two deep-sea sharks, Centrophorus squamosus and Centroscymnus coelolepis, exploited in the North-East Atlantic, B S ZOOL FR, 126(3), 2001, pp. 291-298
Citations number
11
Language
FRANCESE
art.tipo
Article
Categorie Soggetti
Animal Sciences
Journal title
BULLETIN DE LA SOCIETE ZOOLOGIQUE DE FRANCE
ISSN journal
0037-962X → ACNP
Volume
126
Issue
3
Year of publication
2001
Pages
291 - 298
Database
ISI
SICI code
0037-962X(2001)126:3<291:DAROTD>2.0.ZU;2-U
Abstract
Since the end of the 1980s, certain French bottom trawlers have turned thei r effort towards the mid-portion of the continental slope in response to th e scarcity in traditional resources of the continental shelf. The developme nt of this multispecific fishery has lead to the exploitation of new specie s. In particular two deep-sea squaloid sharks, recorded as "sikis", Centrop horus squamosus and Centroscymnus coelolepis, which represent 15% of the la ndings of deep-sea species. Globally, C. squamosus is 1.6 times less abunda nt than C coelolepis. The maximum abundance is recorded in the 800 in depth strata for C. squamosus (10 ind./haul), and in the 1300 in depth strata fo r C. coelolepis (29 ind./haul). For both species. the maximum density is ob served in the Porcupine area (23 ind./km(2)). A specific maturity scale has been adapted from STEHMANN (1987) for these two aplacental viviparous spec ies (type II). In C squamosus. mean size at first maturity is reached at 98 cm in males, 124 cm in females, and in C. coelolepis 86 cm in males, 102 c m in females. C squamosus and C. coelolepis reproduce throughout the year. The asynchrony of the reproduction and lack of knowledge of growth paramete rs make it difficult to estimate the reproductive cycle duration. Length of pregnancy calculated following HOLDEN (1974), in the hypothesis of the gro wth coefficient were K=0.1, reaches 26 months in C coelolepis, and 30 month s in C squamosus. In these conditions, the duration of the entire reproduct ive cycle is estimated respectively at 8 and 9 years. Bathymetric and geogr aphic segregations have been pointed out. Stock assessment is hampered furh er with a significant part of the population not found in the exploited are a including neonates of both species and pregnant and post natal females in C squamosus.