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In an attempt to improve the selectivity of Australian fish trawls targeting tiger flathead, Platycephalus richardsoni (≥28 cm total length), the utility of four-seam codends with shortened lastridge ropes and comprising 71-mm meshes turned 90° (T90) hung at the narrowest and widest coherent circumferences was compared against a traditional 91-mm diamond-mesh (T0) codend. Significant effects of codend configuration were limited to an increase in the catches of another commercially important species, latchet, Pterygotrigla polyommata, by both T90 codends, and greater escape of some small tiger flathead from the wide 71-mm T90 codend than from the 91-mm T0 codend. Notwithstanding a need to investigate slightly larger T90 mesh sizes for the fishery, the data imply that unlike most codend configurations, circumference does not negatively affect selection in the stated designs and might not require future regulation. [ABSTRACT FROM AUTHOR]

Identifying the species response to changing environments can contribute towards proactive and adaptable resource management and, although obtaining observations can be logistically challenging for aquatic species, can be postulated through monitoring.A network of acoustic tracking receivers (n = 93) across south‐eastern Australia was used to identify the effects of environmental conditions on the activity of the yellowtail kingfish (Seriola lalandi, n = 63), an economically important species with a crucial role in pelagic ecosystems. Activity (measured via tri‐axial acceleration) provides an insight into the energetic expenditure of animals, which is linked to movement, behaviour, and physiological processes.Kingfish activity was strongly influenced by sea surface temperature and hour of day, with smaller effects from distance to nearest landmass and bathymetry. Activity also decreased during higher tides and periods of greater moon fraction. Findings show that the energetic responses of kingfish are sensitive to long‐ and short‐term changes, which can regulate behaviours and physiological processes. Changes in kingfish activity and movement (residency and space use) were further investigated at a seasonal aggregation in a small temperate estuary (approx. 120 km2; Coffin Bay, South Australia), where individuals remained during the austral spring and summer (September–April), with a complete exodus in winter. Fifty per cent of tagged fish returned to this estuary in three consecutive years, indicating its importance for aggregating kingfish.While residing in Coffin Bay, kingfish activity varied between interconnected areas, with temperature, hour of day, tide height, and moon fraction again identified as important explanatory variables. These findings have implications for the energetic budgets of large pelagic fish in subtropical and temperate regions, which are facing rapidly changing climates.These results are important for understanding and accounting for the potential responses and physiological impacts of future climatic conditions on migratory pelagic species. [ABSTRACT FROM AUTHOR]

The effects of reducing bar spaces in a generic Nordmore grid used in an Australian penaeid-trawl fishery were investigated within an objective of maximising bycatch reduction while maintaining target catches. Compared to a conventional Nordmore grid with 20 mm bar spaces, those with 16 and 18 mm bar spaces maintained the retained weights of school prawns, Metapenaeus macleayi, and with no effects on size selectivity, but caught incrementally lower weights of total fish, which for the 16 mm grid was significant (mean reduced by ~26%). The results imply that Nordmore grid bar spaces can be reduced to a size approaching the width of the largest penaeids with no commercial impacts., Introduction Concerns about penaeid-trawl discard mortality, and especially juveniles of important fish stocks, have led to various resolution strategies (Hall and Mainprize, 2005). Excluding closures, the most common approach has [...]