Tasmanian scalefish fishery: ecological risk assessment

Two recognised ecological risk assessment (ERA) frameworks were used to identify the potential risks of the various fishing activities in the Tasmanian Scalefish Fishery. The first was a qualitative approach suited to fisheries with limited data and is closely aligned with the standard risk assessment approach utilised in occupational health and safety. The second is a semi-quantitative approach that is suited to fisheries for which data relating to catch, discards, post release survival and technical aspects of the fishery are available. For comparative purposes, this latter approach was applied to the gillnet fishery for which such data are available.

The Tasmanian Scalefish Fishery is a complex fishery involving a variety fishing methods. Each gear was therefore addressed separately. In order to perform the ERA, the fishery was segmented into smaller, more manageable components, namely (i) retained species, (ii) nonretained species and (iii) ecosystem impacts. A series of sub-components were defined to describe the fishing and ecological interactions and for each sub-component, hazardous events and their potential impacts were identified.

Risk analysis considers the source of risk, the possible consequences of the risk and how likely it is that the consequences will occur. Consequences and likelihood are assessed against specific objectives, which differ according to the component of the risk assessment. Consequence and likelihood are combined to produce an estimated level of risk associated with the particular hazardous event in question.

The assessment was conducted as a snapshot in time, capturing the risk profile of the fishery in 2012/13. The risk profile may change over time.

While little is known of the specific impacts of many of the fisheries/gears that are utilised within the Tasmanian Scalefish Fishery, it was possible to rule out major risks in many cases based on low levels of effort and small catches. In many cases the target, by-product and by-catch species encountered by these gears/fisheries are widely distributed and fished through a small proportion of their range. Fishing methods that did not have risk rankings of greater than low include automatic squid jig; beach seine, dip net, fish trap, hand collection, purse seine, spear, and trolling. Each of these fisheries were also assessed to have negligible to low negative impacts on protected species, the broader ecosystem or the physical habitats in which they operate.

Fisheries/gears with medium risk rankings include Danish seine, drop line, handline, octopus pot and squid jig. Only the gillnet fishery had high risk rankings. In the majority instances medium to high risks were associated with target and/or by-product species. As both Danish seine and gillnet methods can involve considerable levels of by-catch, impacts on discard species were ranked as medium risk, primarily due to limited information about the nature of the discards and impacts on the populations. Target species for which the medium risk assessments were made include Striped Trumpeter, Bastard Trumpeter, Sand Flathead, Southern Calamari and Pale Octopus, high risk assessments were for Banded Morwong and Blue Warehou. Medium or high levels of risk dictate that some level of specific management and/or monitoring is required. It is significant that the majority of these species are subject to specific management arrangements (including limited access, total allowable catches, trip limits and/or seasonal closures) as well as on-going biological monitoring programs.

Although many of the fishing methods involve interactions with protected species, for the most part these present a very low risk. Exceptions included Danish Seine which was assessed to pose a medium risk to Spotted Handfish, and gillnetting which poses a medium risk to seabirds and a high risk to Maugean Skate. The rankings for the Spotted Handfish and Maugean Skate are based on the fact that these species are listed as endangered, have small population sizes and very restricted distributional ranges.

Apart from Danish seine, none of the methods pose greater than very low risk to benthic biota. For Danish seine activity a medium risk was identified, however, as fishing grounds tend to be very discrete and extensive areas are closed to the method, the ‘foot print‘ of the fishery is small relative to suitable habitat.