A conceptual framework for enhancing and studying recruitment of marine fish stocks

The possibility of enhancing and studying recruitment of commercially important marine fish stocks is discussed in general, and for North-east Atlantic cod stocks, Gadus morhua L.,in particular . Current knowledge concerning the relative importance of different physical and biological factors influencing survival of early stages is addressed in relation to cost-benefit of release programmes . The cost of producing large juveniles is relatively high compared with the expected yield per recruit . Because large juveniles also eventually become too expensive to release, emphasis should he put into releasing the offspring as early as possible . Special attention is given to evaluation of the optimal time for survival of larvae and juveniles and thus the possibility to enhance recruitment by releasing the offspring when environmental factors are favourable . The prey energy available for larval and juvenile fish varies during ontogeny . The period at the onset of exogenous feeding and the early juvenile period are hypothesized to be critical windows in relation to recruitment . Experimental designs in closed and open enclosures for further investigations of the importance of food availability, predation and cannibalism are outlined, with use of genetic and otolith marking for identification of different cohorts .

[1]  Kristian Fredrik Wiborg.  Investigations on Cod Larvae in the Coastal Waters of Northern Norway - Occurrence of cod larvae, and occurrence of food organisms in the stomach contents and in the sea , 1948 .

[2]  J. Koslow,et al.  Condition of larval cod (Gadus morhua) off southwest Nova Scotia in 1983 in relation to plankton abundance and temperature , 1985 .

[3]  Q. Bone,et al.  Biology of Fishes , 1979 .

[4]  A. Shirota.  Studies on the Mouth Size of Fish Larvae-III , 1978 .

[5]  N. Bromage,et al.  The effect of modifications in photoperiod on spawning time, ovarian development and egg quality in the sea bass (Dicentrarchus labrax L.) , 1989 .

[6]  Kristian Fredrik Wiborg.  Experiments with the Clarke-Bumpus Plankton Sampler and with a Plankton Pump in the Lofoten Area in Northern Norway , 1948 .

[7]  J. Hunter,et al.  EARLY LIFE HISTORY OF PACIFIC MACKEREL, SCOMBER JAPONZCUS , 1980 .

[8]  Gunnar Sætersdal,et al.  Ecological adaptation of reproduction in Northeast Arctic cod , 1987 .

[9]  Kristian Fredrik Wiborg.  Investigations on Zooplankton in Coastal and Offshore Waters of Western and Northwestern Norway - With Special Reference to the Copepods , 1954 .

[10]  D. Cushing.  Are fish larvae too dilute to affect the density of their food organisms , 1983 .

[11]  R. Lough,et al.  Recent growth, biochemical composition, and prey field of larval haddock (Melanogrammus aeglefinus) and Atlantic cod (Gadus morhua) on Georges Bank , 1987 .

[12]  R. Hewitt,et al.  Causes of mortality in young jack mackerel , 1985 .

[13]  K. Brander.  A re-examination of the relationship between cod recruitment and Calanus finmarchicus in the North Sea , 1992 .

[14]  A. Shirota.  Studies on the mouth size of fish larvae. Method and conclusions only [Translation from: Bulletin of the Japanese Society of Scientific Fisheries 36, 353-368, 1970] , 1977 .

[15]  C. Davis,et al.  Seasonal plankton cycles in a temperate fjord and comments on the match-mismatch hypothesis , 1992 .

[16]  John Shepherd,et al.  A mechanism for density-dependent survival of larval fish as the basis of a stock-recruitment relationship , 1980 .

[17]  J. T. Nordeide,et al.  Observations on reared newly released and wild cod (Gadus morhua L.) and their potential predators , 1991 .

[18]  J. Anderson.  A Review of Size Dependant Survival During Pre-recruit Stages of Fishes in Relation to Recruitment , 1988 .

[19]  D. H. Cushing,et al.  Plankton Production and Year-class Strength in Fish Populations: an Update of the Match/Mismatch Hypothesis , 1990 .

[20]  M. M. Smith,et al.  Biology of fishes , 1986 .

[21]  E. Houde,et al.  Predation on Eggs and Larvae of Marine Fishes and the Recruitment Problem , 1989 .

[22]  L. Fortier,et al.  Optimal foraging and density-dependent competition in marine fish larvae , 1989 .

[23]  Torstein Pedersen,et al.  Variation of peak spawning of arcto-Norwegian cod (Gadus morhua L.) during the time period 1929-1982 based on indices estimated from fishery statistics. In: The propagation of cod Gadus morhua L.: an international symposium, Arendal, 14 - 17 June 1983 , 1984 .

[24]  D. Cushing.  The gadoid outburst in the North Sea , 1984 .

[25]  Arild Folkvord,et al.  Growth, survival and cannibalism of cod juveniles (Gadus morhua): effects of feed type, starvation and fish size , 1991 .

[26]  O. Østvedt.  Zooplankton investigations from weather ship M in the Norwegian Sea, 1948-49 , 1955 .

[27]  A. Folkvord,et al.  Allometric growth in juvenile cod (Gadus morhua) and possible effects on cannibalism , 1993 .

[28]  S. Tilseth,et al.  A case study on the distribution of cod larvae and availability of prey organisms in relation to physical processes in Lofoten. In: The propagation of cod Gadus morhua L.: an international symposium, Arendal, 14 - 17 June 1983 , 1984 .

[29]  Arild Folkvord,et al.  Automatic feeding and Harvesting of Juvenile Atlantic Cod (Gadus Morhua L.) in a Pond , 1987 .

[30]  H. Otterå.  Feeding, Growth, and Survival of Atlantic Cod (Gadus morhua) Larvae Reared in Replicate Plastic Enclosures , 1993 .

[31]  A. Folkvord,et al.  Mass Production of Atlantic Cod Juveniles Gadus morhua in a Norwegian Saltwater Pond , 1985 .

[32]  E. Houde.  Fish early life dynamics and recruitment variability , 1987 .

[33]  S. Campana,et al.  Spatial Comparison of Recent Growth in Postlarval Atlantic Cod (Gadus morhua) off Southwestern Nova Scotia: Inferior Growth in a Presumed Nursery Area , 1989 .

[34]  T. Svåsand,et al.  Comparative Survival and Growth of Two Strains of Atlantic Cod (Gadus morhua) through the Early Life Stages in a Marine Pond , 1994 .

[35]  B. Braaten.  GROWTH OF COD IN RELATION TO FISH SIZE AND RATION LEVEL , 1984 .

[36]  D. A. Dwyer,et al.  Feeding Habits and Daily Ration of Walleye Pollock (Theragra chalcogramma) in the Eastern Bering Sea, with Special Reference to Cannibalism , 1987 .

[37]  J. Kane.  The feeding habits of co-occurring cod and haddock larvae from Georges Bank , 1984 .

[38]  I. Huse,et al.  A simple and inexpensive spawning and egg collection system for fish with pelagic eggs , 1983 .

[39]  K. Tande.  Calanus in North Norwegian fjords and in the Barents Sea , 1991 .

[40]  T. Svåsand,et al.  Enhancement studies of coastal cod in western Norway. Part IV. Mortality of reared cod after release , 1990 .

[41]  L. M. Dickie,et al.  Biomass Spectra of Aquatic Ecosystems in Relation to Fisheries Yield , 1992 .

[42]  U. Lie.  Quantities of zooplankton and propagation of calanus finmarchius at permanent stations on the norwegian coast and at Spitsbergen, 1959-1962 , 1965 .

[43]  I. Falk-Petersen,et al.  Morphological changes during metamorphosis in cod (Gadus morhua L.), with particular reference to the development of the stomach and pyloric caeca , 1992 .