This article “Fishery-induced demographic changes in the timing of spawning: consequences for reproductive success” was written by Peter J. Wright & Edward A. Trippel. It is published with the permission of the Controller of HMSO and the Queen's Printer of Scotland.
Fishery-induced demographic changes in the timing of spawning: consequences for reproductive success*
Article first published online: 18 FEB 2009
© 2009 Crown copyright
Fish and Fisheries
Volume 10, Issue 3, pages 283–304, September 2009
How to Cite
Wright, P. J. and Trippel, E. A. (2009), Fishery-induced demographic changes in the timing of spawning: consequences for reproductive success. Fish and Fisheries, 10: 283–304. doi: 10.1111/j.1467-2979.2008.00322.x
- Issue published online: 13 AUG 2009
- Article first published online: 18 FEB 2009
- Received 31 Mar 2008 Accepted 8 Dec 2008
- fishery effects;
- fishery management;
- reproductive potential;
- spawning time
Demography can have a significant effect on reproductive timing and the magnitude of such an effect can be comparable to environmentally induced variability. This effect arises because the individuals of many fish species spawn progressively earlier within a season and may produce more egg batches over a longer period as they get older, thus extending their lifetime spawning duration. Inter-annual variation in spawning time is a critical factor in reproductive success because it affects the early environmental conditions experienced by progeny and the period they have to complete phases of development. By reducing the average lifetime spawning duration within a fish stock, fishing pressure could be increasing the variability in reproductive success and reducing long-term stock reproductive potential. Empirical estimates of selection on birth date, from experiments and using otolith microstructure, demonstrate that there is considerable variation in selection on birth date both within a spawning season and between years. The few multi-year studies that have linked egg production with the survival of progeny to the juvenile stage further highlight the uncertainty that adults face in timing their spawning to optimize offspring survival. The production of many small batches of eggs over a long period of time within a season and over a lifetime is therefore likely to decrease variance and increase mean progeny survival. Quantifying this effect of demography on variability in survival requires a focus on lifetime reproductive success rather than year specific relationships between recruitment and stock reproductive potential. Modelling approaches are suggested that can better quantify the likely impact of changing spawning times on year-class strength and lifetime reproductive potential. The evidence presented strengthens the need to avoid fishing severely age truncated fish stocks.