Strategic R & D plan
This application fits within the Salmon Aquaculture Subprogram.

Reason for need
Currently, variable and unpredictable egg production has a potential opportunity cost for the Tasmanian salmon industry of $15-20 million per annum. Solving this problem is essential for the industry to maintain its continued strong commercial performance; however, the capacity to reach that solution is currently hindered by our limited understanding of the processes that regulate egg shell assembly and how these contribute to chorion and egg abnormalities, and also how these processes change with stock age and rearing temperature. This application addresses the need to overcome that knowledge gap. Industry results to date show that egg survival can be increased through thermal management; however, the relationship between stock age (maidens or repeats) and thermal conditions have not been systematically investigated, and the industry management protocols are essentially informed guess work.

Benefits
The economic viability of sea cage farming of Atlantic salmon is strongly influenced by the cost of production of smolts. Understanding the mechanisms that contribute to, or cause reproductive failure in spawning fish is an essential component of reducing those industry production costs, and at a broader level, ensuring that there are sufficient smolts produced each year to maintain industry production. The issue has been identified as an industry priority with the stated SALTAS aim of reducing the reliance on repeat spawning fish for egg production. The potential cost of failing to solve the problem is high. The survival of eggs to the eyed embryo stage can be as low as 30-50%, compared with 80% for eggs from best performing fish (SALTAS data). Modelling of this cost gives direct increases in smolt production costs of $225,000 per annum, but a potential industry shortfall in production terms of $15-20 million per annum.

The estuaries of Australia’s tropical rivers support commercial fisheries for finfish, crustaceans and shellfish valued at over $220 million per annum. Development of water resources in Australia’s Tropical Rivers region is being considered for the Flinders, Mitchell, McArthur, Roper, Daly and Victoria catchments. The Northern Prawn Fishery also faces threats from land-based development, such as irrigation, and climate change, including changes to sea level. Given the well-documented correlation between flows and banana prawn recruitment, changes to river flows, nutrients, sediments and contaminant inputs are likely to affect fisheries yields (Loneragan and Bunn 1997; Robins et al. 2005). In order to tackle the effect of land-based development, CERF-funded TRACK will co-invest in research in the same river system. This would provide the means to undertake fisheries-targeted research in the wider context of environmental, social and economic research specifically on the Norman River and estuary adjacent to the banana fishery in the south-east Gulf of Carpentaria. This proposal therefore aims to determine how river flow affects estuarine prawn production and emigration. Via the partnership with TRACK, the implications of land use change on river flow, estuarine systems and ultimately prawn juveniles, will be assessed.

The draft management plan by QFMA proposes restrictions on the taking of pipehorses, but also points out that sensible management is impossible without some basic biological knowledge of the species. What is needed is, firstly, to determine catch rates and distributions of pipehorses as by-catch species. Secondly, an understanding of the basic biology of pipehorses is needed. It is important to know population characteristics including the age structure of both sexes, fecundity, longevity and recruitment timing. Specimens are already being collected as by-catch; it is a matter of making scientific recordings on those specimens. It is also important to estimate how far pipehorses move, to know whether they can recolonise areas that have been depleted. Tagging and recapture is probably not useful, as the fish are thought to be in poor condition by the time they are brought to the surface. Genetic methods of estimating movement are needed; modern DNA methods do not even require that the fish be withdrawn from market as only a tiny piece of material from each specimen is required. The pipehorse by-catch issue is being pursued by conservation groups who use syngnathids as symbols of healthy oceans. This is another important reason to implement a sound management plan based on the biology of the species and its interaction with the trawl industry.