Maturation, fecundity and reproductive cycle of spiny dogfish, Squalus acanthias, in the Adriatic Sea

Abstract

We provide the first detailed information on the reproductive traits of the endangered spiny dogfish (Squalus acanthias) in the Adriatic Sea, based upon 224 specimens (132 females and 92 males) collected onboard of commercial bottom trawls between 2005 and 2007. The morphometry of gonads, gonadosomatic index (GSI) and histological examination of gonads were used to analyse maturation and gonadal development of the species. The length at 50% maturity was attained at 504 mm for males and 725 mm for females. Ovarian fecundity ranged from 4 to 18 follicles (mean±SD: 10.8±4.5) and uterine fecundity ranged from 6 to 18 embryos (mean±SD: 10.1±3.9). Total length of embryos with absorbed yolk sacs ranged between 200 and 215 mm. The GSI and the high proportion of mature spermatocysts in the testes suggests that a majority of mating activity occurs in June, November and December, while the seasonal distribution of the largest ova and full-term embryos indicate that ovulation and parturition occur during the summer. In comparison with other study areas, spiny dogfish in the Adriatic Sea attained sexual maturity at smaller sizes and obtained higher fecundity values than fish from other regions.

Keywords:

• Reproductive biology
• sexual maturity
• spermatogenesis
• oogenesis
• Chondrichthyes

Published in collaboration with the University of Bergen and the Institute of Marine Research, Norway, and the Marine Biological Laboratory, University of Copenhagen, Denmark

Published in collaboration with the University of Bergen and the Institute of Marine Research, Norway, and the Marine Biological Laboratory, University of Copenhagen, Denmark

Acknowledgements

This study was carried out within the research projects nos. 119-1193080-3171 and 183-1193080-0831 of the Ministry of Science, Education and Sport of Croatia. We are thankful to all collaborating fishermen for their help in collecting of animals, and to our students Patrik Krstinić, Dunja Jusufovski and Hrvoje Čižmek for their help with dissections and sampling. Special thank goes to Dr. Scott A. Heppell (Department of Fisheries and Wildlife, Oregon State University, USA) for his constructive comments to the manuscript. The manuscript was improved following comments from two anonymous reviewers.

Notes

Published in collaboration with the University of Bergen and the Institute of Marine Research, Norway, and the Marine Biological Laboratory, University of Copenhagen, Denmark