Banded Morwong Ecosystem Interactions

Ecosystem and Habitat Interactions

By-product in the Banded Morwong Fishery is low, which is due in part to the large mesh sizes used for Banded Morwong fishing (~140 mm mesh size). In the Ecological Risk Assessment (ERA) published by Bell et al. (2016), no species achieved a ranking of high vulnerability within the Banded Morwong Fishery due to the minimal gillnet effort on the west coast, the shallow nature of fishing operations relative to depths inhabited to by-catch species, low selectivity of smaller by-product and by-catch species given the large mesh sizes imposed in the fishery, and high post-release survival of many of the key by-product and bycatch species.

During the 2021/22 quota year, Banded Morwong comprised 85% (up 11% compared to the previous quota year) of all fish caught during targeted Banded Morwong fishing trips, with Bastard Trumpeter and Bluethroat Wrasse constituting the most commonly caught by-product species (4% and 3% of the total catch for 2021/22, respectively).

Mortality of Banded Morwong and other scalefish species due to predation and fishery interactions with Australian and New Zealand fur seals is largely unknown and represents another source of uncertainty in the assessment. Seals could cause substantial mortality to Banded Morwong, and are known to damage fishing gear and influence fisher behaviour, all of which is likely to impact catches and catch rates. This is believed to be caused predominantly by individual ‘rogue’ seals which learn to target Banded Morwong gillnet fishing. The proportion of shots in which fishers reported a seal interaction increased in 2021/22 relative to 2020/21, with seal interactions being reported for around 36% of all shots. However, it has been historically unclear how consistently fishers interpret and report a seal interaction, or the effect seal predation has on catches (i.e., how many fish are lost). Additionally, effects on fisher behaviour are poorly understood. A number of fishers have indicated that they are setting a proportion of their nets as a decoy to reduce catch losses through seal interactions. The remainder of their gear is set elsewhere, but the effect of additional nets on seal interactions, or on fisher catch metrics (e.g., effort), is poorly understood.