Aspects of feeding, maturation and osmoregulation in cultured juvenile greenback flounder
Establishment of the long-spined sea urchin (Centrostephanus rodgersii) in Tasmania: a first assessment of the threat to abalone and rock lobster fisheries
Development of an algal bloom monitoring buoy for the Australian aquaculture industry: proof of concept
Final report
A prototype of an automatic algal monitoring buoy was developed for unattended operation in shellfish and finfish farm waters. The instrument employs novel antifouling and self-calibration strategies (subject to a provisional patent ) based on a battery-powered actuator extending into the seawater medium at 15 min intervals both a light source and a solid state sensor from a protective PVC cylinder. The optical sensor measures both ambient light and the signal from a high intensity LED light source, with separate readings being taken after travelling through an optical fibre reference path (internal standard) and after travelling through a 60 cm horizontal path of natural seawater. The optical system is suspended at 1 m depth (can be varied) from a float with the systems control and data acquisition system located above water.
Financial constraints ($20,000 FRDC budget) prevented us to also implement a radiomodem link to laboratory computer as originally planned. We are now seeking further funds to develop the instrument to a commercial stage (estimated market value per unit Aus $10,000) and extensively test its field performance under a range of environmental and algal bloom conditions.
Tactical Research Fund: managing inshore stocks of southern rock lobster for a sustainable fishery
There is clearly a concern in the Tasmanian lobster industry about the status of inshore component of the stock. Catch has declined in a number of areas, despite improvements in catch rates. In the Northeast, catch is at record lows, but CPUE has remained stable, which is a possible indicator of hyper-stability or false stability. The apparent stability in catch rates occurs because aggregations containing a major proportion of the population are fished down, as the fleet moves from one area of good catch rates to the next, resulting in a serial depletion of the aggregations, which is masked by the apparent stability in the fishing block. This can result in a very sudden decline in biomass once the entire block is depleted, posing a serious and immediate risk to the inshore component of the stock. There are two potential sources of this problem. Firstly, the scale of the current assessment model, of eight inshore areas (64m) and three offshore areas (>64m) is not be fine enough to detect localised changes in the CPUE or biomass. Secondly there are changes in fishing practices that have increased effort on inshore stocks, and it is unclear whether the extra effort in these practices is adequately recorded in estimates of CPUE. There has been a recent increase in potting effort, commonly referred to as double night fishing, whereby fishers set and haul their pots twice a night, compared to the standard practice of emptying pots once at dusk and/or once during the day. Currently we have no data on the composition of the catch in double night shots, and what proportion of captured lobsters are handled and released, and in fact what consequence this handling has on the overall health of the fishery.