Long-term recovery of trawled marine communities 25 years after the world’s largest adaptive management experiment

Funded Activity Summary

Foreign trawling off NW Australia (1960-1980s) caused extensive impact on benthic and fish communities reflected in a 2-orders of magnitude reduction in sponge bycatch and high value emperor fish stocks giving way to low value lizard fish and threadfin bream. This process was investigated in the largest ever adaptive management experiment on a commercial fishery using a series of closures in the 1980s-early 1990s. This gave rise to the current management arrangements for the Pilbara Trawl Fishery which has protected some previously heavily trawled areas in long term closures. A quarter century on, this situation and the awarding of 4 weeks RV Investigator time in late 2017 provides the opportunity to quantitatively examine >35 years recovery of trawled habitat and to determine whether the climax community of large sponges and the fish communities they supported ever fully recovered. NW Australia is uniquely able to provide long term information for VME habitats that is directly applicable to several trawl fisheries in northern Australia and is potentially the only source of such information internationally for adoption by FAO/MSC. Further, NW Australia is uniquely able to test new methods proposed for Ecological Risk Assessment of seabed impacts and validate their reliability. Lastly, both the Pilbara Trawl and Trap Fisheries are looking towards Fishery Improvement Plans and/or MSC certification and will require the information obtained in this project.

Objectives:
1. The overarching goal of this project is to determine the extent to which trawled communities of the NWS have recovered from high levels of trawling activity prior to the exclusion of foreign fleets (1990) and subsequent to the imposition in the early 1990s of the current tightly controlled spatial management of both trawl and trap fishing effort. By contrasting the diversity, abundance, biomass and size/age composition of the demersal fish community and epibenthic, habitat forming invertebrates across these gradients of historical and recent fishing effort, and by comparing these measures with data collected in the 1980s, we aim to make firm conclusions about the long term rates of recovery of habitats from foreign trawling in the 1960s, 1970s and 1980s and to evaluate how well the current spatial closures, controls on effort and fishing practices are performing from the point of view of sustaining healthy benthic habitats. We will test the prediction that areas where trawling has been dramatically reduced will be characterised by re-establishment of benthic habitats with greater coverage and complexity of larger habitat forming filter feeder communities, and of higher production of key fish (families: Lethrinidae, Lutjanidae), compared to previously and currently trawled habitats. The study will also take into account other environmental parameters which influence both the distribution of benthic and demersal community assemblages and their rates of recovery.

Funded Activity Details

Start Date: 01-11-2017

End Date: 29-09-2019

Funding Scheme: Funding Scheme not available

Funding Amount: $400,000.00

Funder: Fisheries Research and Development Corporation

Research Topics

ANZSRC Field of Research (FoR)

There are no FoR codes available for this funding activity

ANZSRC Socio-Economic Objective (SEO)

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Other Keywords

Bycatch | Fisheries Management | Fishing Gear | Habitat | Marine Park | Risk reduction | Sustainability | Threatened Endangered Protected Species

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