Developing an independent shallow-water survey for the Western Rock Lobster Fishery: tracking pre-recruitment abundance and habitat change.
Department of Primary Industries and Regional Development (DPIRD) Hillarys
Simon de Lestang
The current method of measuring undersize lobster abundance (PRA) is based on catch data adjusted for multiple biases inherent in commercial monitoring, namely: water depth, water temperature, swell, fisher experience, pot type, escape gaps, pot pulling time, month and location. Biases are exacerbated by recent poor sample sizes, as many fishers choose not to fish in shallow-water areas. Developing a standardized, repeatable survey in shallow areas will provide an improved index of PRA that can be incorporated into the stock modelling: this would improve the overall assessment. Currently fishery-independent survey data collection requires a minimum of two staff to process the catch and record information. Data entry is conducted by a third staff member. To increase cost effectiveness (for this and other lobster surveys), a more efficient data collection system is needed. Initial scoping has identified a number of possible solutions (e.g. app-based entry). This project will expand on this original scoping work to develop a solution. This will also benefit commercial lobster monitoring work conducted by DPIRD as well as a range of other surveys in similar pot based fisheries. This survey will also provide a platform for monitoring inshore WRL habitats. This will establish a baseline against which further research into the relationships between WRL and their near shore habitats can be undertaken. This will assist with detecting and quantifying habitat shifts that may impact the fishery. For example, there is anecdotal evidence that the heatwave temporarily modified some of these near shore habitats, leading to the altered relationship between puerulus and lobster recruitment. Long-term monitoring of juvenile habitats will likely provide a useful indicator of one of the factors affecting recruitment to the fishery.
1. Produce accurate measures of pre-recruit abundance throughout the West Coast Rock Lobster Managed Fishery. Compare with commercial monitoring undersize lobster abundance and puerulus settlement data.
2. Design and construct a more efficient data recording tool to increase the accuracy and speed of data collection.
3. Develop base-line habitat descriptions at all potting locations throughout the shallow water survey.
4. Determine the relationship between sampling rate required to detect different magnitudes of marine habitat change at these survey locations