Hawkesbury-Nepean Bass Anglers
Bass are one of the premier sport fish of the NSW eastern drainage rivers as such they are classified a recreational species in NSW, hence cannot be commercially harvested (van der Walt et al. 2004). They are catadromous, migrating downstream during winter months during flood periods to spawn in brackish water estuaries (Harris 1986). This migration can be inhibited where dams and weirs are constructed (Harris 1988).
Bass are also long-lived, up to 22 years (Harris 1985a) and are euryphagic carnivores making their populations resilient in their fluctuating environment (Harris 1985b).
The Hawkesbury River is important in that it is large freshwater eastern drainage system encircling Australia’s largest population centre, Sydney.
This report examines the data collected from Hawkesbury-Nepean Bass Angler Association’s events with respect to the status of bass in the Hawkesbury Nepean River. This is also compared to other rivers in central NSW.
Effort
The Hawkesbury-Nepean Bass Anglers hold two events, the Hawkesbury-Nepean Bass Interclub Challenge as well as their regular point score events. The interclub events have averaged 40 participants and the average number oin point score events has been 13.5 anglers.
The number of events monitored has increased from one per year for the early years to 10 point score and three interclub events in 2005. The monitoring represents 1092 angler days , 7028 hours reported fishing and 4330 fish caught.
The average number of anglers fishing per day for all events was 21. The average fishing effort per event-day was 6 hours per angler day over the series.
Table 1. List of effort as number of anglers and fishing effort as hours per day for Hastings Basscatch events monitored
There were seven species of fish reported; bass were dominant in the catches. Of the 4264 fish that were identified to species 4072 were bass (95.5%). There were 71 bream caught (1.67%) and 62 estuary perch (1.45%) and flathead, 38, tailor, 11, herring, 8, and mullet, 1. The number of bass caught per year ranged from 9 in 1996 to a maximum of 841 in 2004, the year with the second most angler days, 138.
The proportion of bass has ranged from 88.5% in 2005 to 100% in the three earliest years. The diversity appears to have increased in recent years, this may be an artifact of reporting or it may be due to the drought increasing salinity of the river and hence adding saltwater species in the catch.
Figure 1. Species composition as number of fish at Hawkesbury-Nepean Bass events by year.
Figure 2. Species composition as percentage of catch at at Hawkesbury-Nepean Bass events.
Catch rates of bass have been moderate in the at Hawkesbury-Nepean Bass events. Overall the daily catch rate has averaged 5 fish per hour, and 0.64 bass per hour where hours were recorded. While there appears to be a slight increase in the catch rates per day the catch rates per hour are have no trend. Where there were events over a series of months the lack of trends through months is also clear.
Figure 3. Daily catch rates of Australian Bass for Hawkesbury Nepean Bass anglers fishing events in the Hawksbury-Nepean river complex.
Figure 4. Hourly catch rates of Australian Bass for Hawkesbury Nepean Bass anglers fishing events in the Hawkesbury-Nepean river complex.
Other events are also held on the Hawkesbury, when the catch rates from all Hawkesbury events are combined there appears to be a decline in catch rates since the late 1980s. This may be due to many factors including population declines due to anthropogenic or environmental reasons or a factor of the different events themselves or reporting by anglers. In comparison to bass catch rates held on other eastern drainage rivers in central NSW (Regions 8 & 9) the Hawkesbury had the highest catch rates in the early period of monitoring though the decline has brought it to similar catch rates as the Myall and Patterson rivers. The Williams River has now the highest catch rates in these central NSW rivers.
Figure 5. Mean CPUE (fish per hour) for bass for all events at eastern drainage rivers in central NSW.
The mean size of Australian bass at the Hawkesbury Nepean Bass events average 222 mm and ranged between 211 (2002) and 240 (2001). The largest fish recorded was 473mm in 1999. Mean sizes were lowest during years when significant numbers of the smallest fish were evident in the length frequencies.
The mean sizes of bass on the Hawkesbury Nepean Bass events are similar to the averages of other central NSW rivers except that of the Myall which has relatively large bass (though the catch rates are lower).
Figure 6. Maximum, minimum and mean sizes of bass caught at Hastings Basscatch events.
Estuary perch averaged 259 mm with 371 mm the largest estuary perch caught.
Figure 7. Maximum, minimum and mean sizes of bass caught at Hastings Basscatch events.
Figure 8. Mean size of bass from all monitored events in central NSW rivers.
Figure 9. Length frequencies of bass from Hawkesbury-Nepean Bass Angler events
There appears to have been a recruitment event in 2001 that progresses through the size categories in subsequent years.
Summary
The nominal catch rates of bass in Hawkesbury Nepean Bass events are moderate and annual averages appear stable. Though the catch rates for all tournaments monitored in the Hawkesbury have declined since the late 1980s. There appears to have been some recruitment in 2001. Though the proportion of natural recruitment to stocking is unclear. Recruitment has been low since this year, perhaps due to the current drought conditions. The size range of and size distribution suggests there is moderate mortality on the stock as shown by the consistent right hand slope on the length frequencies.
Table 2. Stocking history of Australian bass in the Hastings River
References
• Harris JH (1985a) AGE OF AUSTRALIAN BASS, MACQUARIA NOVEMACULEATA (PERCIFORMES: PERCICHTHYIDAE), IN THE SYDNEY BASIN. In.
• Harris JH (1985b) DIET OF THE AUSTRALIAN BASS, MACQUARIA NOVEMACULEATA (PERCIFORMES: PERCICHTHYIDAE), IN THE SYDNEY BASIN. In.
• Harris JH (1986) Reproduction in the Australian bassMacquaria novemaculata (Perciformes Percichthyidae) in the Sydney Basin. Australian Journal of Marine and Freshwater Research 37, 209-235.
• Harris JH (1988) Demography of Australian Bass, Macquaria novemaculata (Perciformes, Percichthyidae), in the Sydney Basin. Australian Journal of Marine and Freshwater Research 39, 355-69.
• van der Walt B, Faragher RA, Harris J (2004) Comparative angler catches of Australian bass (Macquaria novemaculata) in three major river systems in New South Wales, Australia.
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Angling Research Tournament Monitoring Programme 
