The southern sea garfish is the popular garfish species caught by anglers in Port Phillip Bay and other Victorian bay and coastal waters. Recent estimates of total Victorian recreational catches are around 22 tonnes per year, compared to commercial catches of around 80 tonnes.
During May, DPI Fisheries Victoria held a garfish stock assessment workshop at the Marine and Freshwater Fisheries Research Institute (MAFFRI) in Queenscliff. Fisheries Managers and MAFFRI researchers met with representatives of VRFish and experienced garfish anglers and heard from commercial fishers, to review fisheries trends and assess the current state of southern sea garfish stocks in Victoria.
In both the recreational and commercial bay and inlet fisheries, garfish are regarded as a secondary target species compared with more sought-after finfish such as snapper and King George whiting. Competition for garfish among fishers is therefore not great and the main management objective is to ensure that fishing remains sustainable. This recognises the natural variability in garfish numbers mainly resulting from year-to-year environmental fluctuations. Given the pressures on fish habitats in Victorian bays and inlets, a second management consideration is the identification of habitats that are critical to garfish reproduction and growth.
Southern sea garfish occur from southern Western Australia to New South Wales. While there is genetic evidence of separate stocks across southern Australia, there is also evidence that garfish are capable of travelling distances of hundreds of kilometres. They commonly occur in inshore marine waters less than 20 m deep, particularly over seagrass, and they are also seen several kilometres offshore in open coastal waters.
Adult and juvenile gars school together. During the day they are usually close to the bottom where they feed on algae and other life attached to seagrass and seaweed. At night they feed near the surface on small crustaceans. Spawning occurs mainly between October and March with each female attaching multiple batches averaging 760 large eggs to seagrass and algae. At this time, adult females school up in shallow water while males are more dispersed offshore.
Growth is rapid for the first three years with lengths averaging 17cm after one year and 27cm after three years, with sexual maturity reached at 18 months. Females grow to larger sizes than males and most gars over 30cm are females. Garfish caught and kept by anglers are mainly two-year-olds in Port Phillip Bay and one-year-olds or two-year-olds in Corner Inlet. Very few gars live to six years, indicating a high natural mortality rate. There is little direct evidence of natural predators, but pelagic species such as Australian salmon, pike and calamary – as well as sea birds – are thought to contribute to this high mortality rate.
Annual spawning success and subsequent survival of sea garfish through larval and juvenile stages is highly variable and can lead to large differences in the strength of successive year classes. This in turn affects recruitment to fisheries and can have a big impact on catches from year to year.
National and Victorian surveys of recreational fishing indicate that Port Phillip Bay is the main source of garfish caught by anglers (70–80% of the annual state total), with smaller catches taken from Western Port Bay and the Gippsland Lakes. Recent estimates put the total annual Victorian recreational catch at 22-25 tonnes. Creel surveys show that most recreational catches are taken during the October – March period by anglers using size 6-8 long shank hooks, baited with pipi, prawn or fish, under floats. Unlike many other species, around 20-30% of garfish are caught by shore-based anglers fishing from piers, rocks and breakwaters. Small quantities of gars are also taken by dip-netting in shallow waters on ocean beaches and in estuaries in western Victoria.
Most of the annual commercial catch of gars is taken during winter and comes from Corner Inlet (60%) and Port Phillip Bay (30%), mainly from areas of healthy seagrass beds. Smaller catches – along with some river garfish – are taken in the Gippsland Lakes.
Most commercial catches are taken by haul seining, one of the netting methods banned in Western Port Bay from December 2007, hence the discontinuation of catches there. In 2007/08 the total Victorian commercial catch was 72 tonnes with a wholesale market value of about $0.5 million. Eighteen of the 66 licensed operators accounted for 90% of the total catch. Recent declines in commercial fishing effort and garfish catches are not surprising given that the number of licensed bay and inlet commercial fishers has been reduced from more than 260 in 1985/86 to fewer than 80 today. However garfish catch rates – while variable from year to year – have shown no longer term declining trend. Short term downturns in commercial garfish catches and catch rates often occur at the same time as upturns in catches of the more valuable King George whiting when they are more abundant.
The limited available fishery and scientific information indicate that the southern sea garfish stocks in Victorian waters are in reasonably good shape. There are, however, several factors that make it hard to be more definitive about this assessment. In addition to the environment-driven variability in annual reproductive success and year class strength, there is poor understanding of garfish movements between bays, inlets and open coastal waters and how this might affect localised abundance and availability. Interpreting commercial garfish catch and effort data as an indicator of garfish abundance is also confounded by the tendency for targeted fishing effort to switch away from or back to garfish depending on the abundance of the more highly valued King George whiting. Continual changes to the distribution and abundance of seagrass beds in Port Phillip Bay and Corner Inlet – and the unknown factors behind these changes – further confuse the situation.
Collection of fishery and scientific information on garfish is likely to be limited for as long as this species remains a by-catch or secondary target species, making it difficult to draw more concrete conclusions about the stocks by relying on current fishery monitoring approaches. However, the workshop discussed some improvements that may be feasible, including recruiting anglers who specialise in gar fishing – from piers/shore as well as boats – to MAFFRI’s angler diary program. Closer analysis of targeted commercial gar fishing operations may also help. Given the more urgent need for improving assessment capabilities for some other species (eg snapper and black bream), there’s a clear need to use current monitoring resources more effectively if more detailed information on garfish is to become available.
It’s clear that there’s a lot we don’t know about garfish. What is the relationship between those fish found in the bays and inlets and those found out to sea in ocean waters? What happens to the vast numbers of juvenile gars seen in the bays at times – do they die quickly and in large numbers or do many move out into coastal and offshore waters? Are the shallow bays and inlets the source of all garfish in Victorian and adjacent waters? What is clear is the critical importance of the shallow seagrass beds and weedy reef areas in sheltered inshore marine waters. If we needed another good reason for ensuring the protection of these habitats, we can add safeguarding the garfish stocks.Reads: 10569