Status of the recreational fisheries in two Australian coastal estuaries following large fish-kill events

Severe flooding occurred during early 2001 over a widespread region of northern New South Wales (NSW), Australia. This flooding was followed by large scale mortalities of invertebrates and finfish in the Richmond and Macleay estuaries. These estuaries were then closed to all forms of recreational and commercial fishing to enhance the recolonisation and recovery of their fish populations. The lower reaches of these estuaries were re-opened to limited fishing after closure periods of 4.5 months (Richmond) and 3.5 months (Macleay). Complemented angler surveys, based on stratified random sampling procedures, were used to assess the subsequent recovery of these important estuarine recreational fisheries. Historical information from the Richmond and Clarence estuarine fisheries and data collected during recent estuarine recreational fishing surveys in other areas of NSW were used as relative benchmarks to compare the post-fish-kill survey data. These comparisons indicated that at the time of the post-fish-kill surveys these fisheries were characterised by normal temporal trends in fishing effort and typical seasonal harvests. Similarly, three indicators of recreational fishing quality were shown to be of similar magnitude to comparable measures from other estuarine fisheries in NSW. All comparisons indicated that the recreational fisheries in the lower Richmond and Macleay estuaries had recovered and were providing good quality recreational fishing opportunities. Luderick (Girella tricuspidata), yellowfin bream (Acanthopagrus australis) and dusky flathead (Platycephalus fuscus) together accounted for 93.9% (Richmond) and 91.7% (Macleay), by weight, of the recreational harvest. Length frequency distribution data for these species taken by boat-based fishers were compared between estuaries. No significant differences between estuaries were detected for luderick or yellowfin bream indicating that legal sized recruits recolonising these estuaries after the fish-kill events were derived from larger meta-populations which spanned a spatial scale of at least 200 km (the distance between the estuaries). These results suggest that for luderick and yellowfin bream the deleterious impacts of localised catastrophes, even on the spatial scale of a large estuary, can be mitigated rapidly by immigration from other areas. In contrast, the length frequency distributions of dusky flathead that were present in the Richmond and Macleay estuaries during the survey period were highly significantly different indicating that they had originated from different source populations. The more localised scale of recolonisation evident for dusky flathead indicates that this species may be less resilient to localised catastrophic events than luderick or yellowfin bream. This study highlights the value of recreational fishing surveys for providing insights about the factors that may influence the recolonisation and recovery of estuarine finfish populations following large fish-kill events.