Coastal stocks of fish: from which estuaries are most adults derived?

Funded Activity Summary

The origins of many stocks of fish are unknown. As juveniles, many fish are found in estuarine regions. After a period in these habitats they may leave estuaries for coastal reefs and shelf waters. Degradation of habitats within estuaries (from pollution, land reclamation, marinas etc) and death of fish as by-catch in commercial and recreational fishing may affect abundances of adults on coastal reefs. The contribution of each estuary to total stock size in coastal waters is unknown. It is difficult to determine which estuary adult fish may have come from using conventional tagging methods, because of the small size of fish in estuaries. Alternative methods for determining the origins of adult fish are needed.

Molecular genetics provides one possibility, but these methods are in their infancy. An alternative method may utilise chemical elements in bones to show origins of fish. Chemical analyses have proven useful in distinguishing between periods of freshwater and marine residence within individual fish (e.g. Kalish 1990) and have also been used to distinguish stocks or sub-populations within marine species (e.g. Edmonds et al. 1989, 1991, 1992, 1995). Recently, we (Gillanders and Kingsford 1996) have used chemical analyses of ear bones to distinguish recruits that settled to seagrass from those that settled to reef habitats. We then analysed the centre region of adult ear bones to determine the origin (estuary or reef) of adult fish showing that this approach is possible.

Many studies have documented important estuarine "nursery" areas in terms of numbers of fish, but if few fishes from these areas reach coastal reefs, such habitats may be relatively unimportant to sustaining populations of adults. The research will focus on snapper (Pagrus auratus) because it is the most important species (in terms of production) that has individuals leaving estuaries for coastal reefs or shelf waters (Bell and Worthington 1993).

Objectives:
1. To solve a pressing problem for the fishery by determining what proportion of the commercial catch is from different estuaries.
2. To use methods being developed on juvenile fish to establish a chemical "fingerprint" for each estuary so that in future years the proportion of adults from each estuary can be determined.

Funded Activity Details

Start Date: 21-06-1998

End Date: 13-06-2002

Funding Scheme: Funding Scheme not available

Funding Amount: $142,684.00

Funder: Fisheries Research and Development Corporation

Research Topics

ANZSRC Field of Research (FoR)

There are no FoR codes available for this funding activity

ANZSRC Socio-Economic Objective (SEO)

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Other Keywords

Biomass | Estuarine | Fisheries Management | Habitat | Otolith

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