CSIRO Marine and Atmospheric Research
Past Seminars

Friday, 12 September 2003 11.30am (Tas time)

CSIRO Auditorium and via videoconference to Floreat and Cleveland

Dr Per Solemdal
Institute of Marine Research, Bergen, Norway

Recruitment mechanisms based on environmental and maternal factors and a way to combine them

Most population models used for fishery assessment require specification of a relationship between the present spawners in the population and the subsequent number of young fish (recruits) they produce. Often this specification is in the form of a relationship between the present weight of mature fish, the spawning stock biomass, and subsequent recruitment. But there has been considerable difficulty in specifying this relationship. Annual recruitment variation is often large and not well correlated with spawning stock biomass. Annual variation in the marine environment influences the survival of offspring. And both the number of spawners and recruitments is measured with error.

During the last few years it has been increasingly recognized that the characteristics of the female spawners are very important in determining the number of recruits that are ultimately produced. These characteristics include the age (experience), size, and condition of females. These characteristics can affect the quality of eggs, embryos and larvae - and ultimately their survival.

Recruitment mechanisms caused by environment and maternal factors will be discussed, and a suggestion to combine the two types of recruitment mechanism.

 

Per Solemdal has been working at the Institute of Marine Research, Bergen, Norway, since finishing University studies at Bergen University, 1968. Main study object has been different aspects of reproduction and recruitment mechanisms in cod Gadus morhua L. Periods of Norwegian marine biology history, artificial bait for long line fishery and studies of pelagic eggs in brackish and marine areas.

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