The FRDC recently commissioned a review of the importance of seagrass habitats to fisheries sustainability in which Connolly et al. (in press) identified the "gaps in our understanding and future research needs" and made "recommendations for future research" (In Press: Report No. 98/223).
Connolly et al. (in press; point seven, section 6.4. Gaps in our understanding and future research needs) suggest that the nature of the links between fish and processes such as "feeding, protection from predators and amelioration of physical disturbance" within seagrass habitats are "poorly known". "Hard data on links between seagrass and fishery species are needed urgently" (Connolly et al., in press; section 6.5. Summary of recommendations for future research). Connolly et al. (in press) identify a need for "small scale manipulative experiments", "conducted over a large enough spatial scale" so that we can increase our capacity "to predict the effects of changes in seagrass extent on commercial fish". It is important to understand the importance of "processes linking seagrass with fish" in order to be "able to predict the effects of seagrass changes on fisheries" (Connolly et al., in press; section 6.5. Summary of recommendations for future research).
Connolly et al. (in press) also suggest that "dietary and isotope studies of piscivorous fish are required " because the role of small, non-commercial species in food chains for commercial species is only known in localized areas" (section 6.4. Gaps in our understanding and future research needs, point 12, section 6.5. Summary of recommendations for future research). Isotope studies will also address the need for research which compares the ecology (e.g. extent of assimilation of food from seagrass beds) of fishery species that spend all or only part of their life associated with seagrass" (point 3, section 6.5. Summary of recommendations for future research).
Cappo et al. (1998) reiterate Connolly et al. (in press) in suggesting that information is needed about the role of predation in structuring fish assemblages within seagrass beds. "There is a surprising lack of basic life-history information for most of the major fishery species in Australia", and "consequently a paucity of information on "critical" habitat requirements and processes such as post-recruitment mortality" (section 1.3.4 Lack of knowledge of links between life-histories and habitats).
Final report
This project has increased our understanding of the importance of seagrass habitats to larger, commercially valuable, species of fish by combining experimental and correlative scientific principles. We found that many small fish use seagrass habitats for nutrition and to avoid predation by large predatory fish. Some of these small fish also form important parts of the diets of commercially important species, such as Australian Salmon. The importance of predatory fish varied, however, from site to site, suggesting that seagrass habitats may need to be evaluated individually. The primary outcomes of this study will be important in identifying seagrass habitats that are especially valuable as feeding and nursey sites for commercially valuable fish in Port Phillip Bay. The type of information presented in this study will help understand how and why various nearshore marine habitats may be used by various species of fish, and how best to ensure their protection and future sustainability.
