Barramundi - north east coast monitoring

Biological monitoring update

There are six genetic stocks (Keenan,1994) of barramundi along the Queensland coast. This fact sheet provides results for biological monitoring for the north east coast barramundi stock (see Map).

Since 2007, commercial and recreational fishers, and seafood wholesalers have been assisting with the collection of length, sex and age data of fish being retained from this fishery. To estimate the age of fish, otoliths (ear bones) are removed from the head of fish. The otoliths are set in resin so that thin sections can be cut and examined under a microscope. This technique enables a clearer view of the annual bands for this species. The number of bands indicate the fish's age.

The sustainability of our barramundi fisheries is evaluated regularly with the assistance of the biological data gathered by this program. Catch and effort information from commercial fishing logbooks and surveys of recreational fishers also plays an important role in these assessments.

Monitoring results

Barramundi can be retained by commercial and recreational fishers within the legal size range of 58 cm to 120 cm total length. However, fish over one metre are rarely harvested.

The 2015 results show a higher than usual proportion of seven and nine year-olds in the catch. These are the result of particularly strong year classes spawned in the wet seasons of 2006-2007 and 2008-2009 .

Freshwater flows, warm sea temperature and low evaporation during intense monsoonal seasons favour the breeding success and survival of juvenile barramundi (Robins et al. 2004, Balston 2009). The lack of strong year classes entering the fishery in recent years, is not surprising as the monsoon season in the tropical areas of Queensland has been mild over recent years.

Most barramundi will reach the maximum legal length by 10 years old, although some do grow slower. The oldest barramundi sampled so far from the north east coast stock was 27 years old and was caught in 2013 (Table 1). Of the 6906 north east coast barramundi aged since 2007, only eight have been greater than 20 years old.

Table 1. Fish over 20 years old recorded by the program from 2007-2015.

The age of a barramundi from the north east coast can be estimated using Graph 3. Look up a total length and find the corresponding age on the graph. For example, at 83 cm barramundi are likely to be five years of age, although they can easily range between three to eight years old.