Ensuring Monitoring and Management of By-catch in Southern Rock Lobster Fisheries is Best Practice

By-catch is an important issue in fisheries worldwide, with the impacts of fishing activities on non-targeted species and the wider marine environment receiving increasing public attention. Issues such as the potential wastage of resources through discarding of unwanted catch, ecological impacts on non-targeted species, and the possibility of negative impacts on Threatened Endangered and Protected Species (TEPS) have led to an expectation that government and other managers will report on the status and impacts on these species. In order to do this effectively, well designed monitoring programs need to be in place. Effective by-catch monitoring programs allow researchers to understand which species are important as by-catch across a fishery, how the quantity of by-catch is changing through time, and any potential risks to by-catch species.

IMAS researchers have led the most in-depth analysis of by-catch across the entire Southern Rock Lobster Fishery (SRLF) to date, involving researchers, stakeholders and managers across South Australia, Victoria and Tasmania. We use information from independent scientific observer programs and scientific research cruises collected over a period of greater than 15 years to:

(i) Explore the important by-catch species in each state and management zone;
(ii) Conduct a critical appraisal of the current monitoring programs by comparing them to international best practice;
(iii) Help inform a risk assessment for all by-catch species through workshops held in each state involving key stakeholders including researchers, fishers, fisheries managers, scientific observers involved in the monitoring programs, scientific experts and ecologists.;
(iv) Explore quantities and trends in by-catch for species deemed to be at moderate risk from fishing activities.

Important by-catch species in terms of frequency, total number and weight varied across the states and management zones but generally included wrasse, leatherjackets, perch, octopus, crabs (hermit, velvet and giant) and sharks (Draughtboard Sharks in Tasmania and Eastern Victoria, and Port Jackson Sharks in Western Victoria and South Australia). Undersized Rock Lobsters, which are also considered by-catch, formed a large component of the overall bycatch particularly in Tasmania.

The current by-catch monitoring program was assessed against international best standards defined under the United States Tier Classification Scheme developed by the National Marine Fisheries Service. We found that each state managed program fell into a Tier 2 classification out of five possible tiers ranging from 0 to 5. This score was reasonable when comparing the programs in other fisheries given the size of the SRLF. However, areas for improvement in the observer programs were identified and recommendations on how to improve the ongoing monitoring program are made in light of our findings.

The risk assessment found that no by-catch species was at high risk from fishery operations of the SRLF. Species that were identified as having a medium potential risk were a subset of those that are kept as by-product either for consumption, sale or bait. Barotrauma was also identified as a risk factor for some finfish species with swim bladders as these species when brought up from depth may suffer injury or be unable to descend and thus more susceptible to predation. Also, missing life history information for a number of species meant that precautionary higher risk scores were assigned to these species until more information is obtained. Rates of encounter with gear of Threatened, Endangered and Protected Species (TEPS) were found to be low, and consequently direct threats from fishery operations likely to be low; however, ongoing monitoring of TEPS interactions is a necessary component of best practice.

A short list of ten species identified as being more susceptible to risk from the SRLF were given further analyses. These ten species included Draughtboard Shark, a number of leatherjacket species, Ocean Perch, Blue-throat Wrasse and Conger Eel. Analysis of these species and groups allowed for estimates of total catch of these species and trends in catch through time. These estimates provide a baseline for ongoing monitoring and the setting of reference points for management action for these species. Based on the findings of this report, it is recommended that:

• Improvements are made to the observer programs including increasing the number of vessels participating, creation of consistent reporting methods, improved species identification
• Information is collected for by-catch species with missing life history parameters to allow increased confidence in future risk assessments
• Species identified in this report as being of primary or secondary importance as by-catch in the SRLF are prioritised for ongoing reporting and monitoring, with a periodic census of all by-catch species (perhaps every 5 years) used to detect any trends in overall by-catch composition
• Due to the considerable noise in by-catch data, longer-term trends are used as management trigger points
• Further research is conducted into reducing the amount of undersized Rock Lobster

You can read the full report on the spatial overlap by Leon et al. (2019) at the link: