IT HAS been another big year for the Queensland Department of Primary Industries' Northern Fisheries Centre (NFC) in Cairns, with the opening of a new research facility, the production and stocking of nearly 250,000 barra fingerlings and the continued research into breeding mangrove jacks in captivity.
Construction of the $8.2 million addition to the Fisheries Research Centre in Cairns was completed in 2002, with the official opening on December 13 by the Minister for Primary Industries, Mr Henry Palaszczuk. The project included a new 1650sqm research and development facility, relocation of existing breeding and research tanks and refurbishment of the existing building. The upgraded Northern Fisheries Centre is now one of the most advanced fisheries research facilities in Australia.
This season's barramundi breeding at the NFC has involved three spawnings, with the first producing 103,133 fingerlings, the second 90,000 fingerlings, and the final spawning yielding another 50,000 for release in late March. Stocking has been conducted at 10 different locations in estuaries, rivers and impoundments between Mackay and Cooktown.
To promote greater survival rates, all fingerlings released this season have been 50mm and larger. Current research supports greater survival rates for larger fingerlings, and initial research conducted in the Johnstone River (in Innisfail) has shown a particularly high survival rate for fingerlings released in the 300mm size range. This prompted the Cairns Fish Stocking Society (formerly the Mulgrave Fish Stocking Society) to release a batch of 3000, 300mm fingerlings into Trinity Inlet in mid-December 2002. All barra were individually tagged on release, which was a mammoth all-day task for NFC staff and members of the fish stocking group.
The hard work has already been paying dividends, with the first recapture recorded a week after the release. Another young angler reported the capture of seven tagged barra in late January, in the upper reaches of the Inlet, but unfortunately he didn't record enough details to be really helpful to researchers.
Anglers are reminded that if they capture any tagged fish, to record the serial number, fish length, time, date and location of the capture and pass it on via the phone number shown on the tag. Releasing the fish again is also a great help to researchers, as many tagged fish have been recaptured on multiple occasions, offering extremely valuable data for researchers about the long-term movements of fish.
Anglers don’t have to give away the location of their secret snag, but enough information so researchers can determine the movement of the fish since capture. For example, ‘the upper reaches of Chinaman Creek’ is far more useful than just ‘Trinity Inlet’. All anglers who report a capture of a tagged fish receive a certificate for their efforts and, wherever possible, feedback on the history of that particular fish.
While research is showing that bigger fingerlings have better survival rates, the major problem to date has been obtaining these bigger fish. At 300mm, barra are ideal for the restaurant market as plate-size fish, so stocking groups have to pay near to commercial prices for these fingerlings. I think I know which fate the barra would prefer!
Mangrove jack have continued to be a challenge for the NFC, with the first spawning attempt failing when the broodstock didn't want to play the game. Although the female jacks swelled up, indicating they were ready to spawn, they didn't release and consequently the males weren't interested.
A second attempt was aborted because of salinity levels being too high in the Townsville area, where the jack spawning program is based. Another attempt was made in late January, using a different hormone to induce spawning to the one used in the first round. This attempt has resulted in a successful spawning, with researchers waiting anxiously to see whether the larvae survive in the new rearing conditions.
The major bottlenecks with the successful breeding of mangrove jack still seem to be obtaining consistent spawning and then larval rearing once the spawning has taken place. Breeding jacks in captivity is as simple as many anglers would think!
Once released, the hatchery-bred jacks are proving very adaptable, with fish released into a closed impoundment during initial research being recaptured by researchers at up to 400mm long. The jack fingerlings released into Tinaroo Dam continue to thrive, with legal length recaptures recorded in less than three years after release. Of the total of 4478 jacks released into Tinaroo there have been 13 confirmed recaptures by recreational anglers, as well as seven recaptures by researchers using electro-fishing equipment.
NFC stocking has contributed to about one third of the stocking conducted in North Queensland, with the remainder of fingerlings being produced by commercial hatcheries. With more and more money being funnelled into fish stocking from revenue raised from the Stocked Impoundment Permit Scheme, this can only help to improve the fishing for anglers in the North.
1) Warren Lindsay, from Redland Bay, with a 108cm barra. This fish is one of the huge number of stocked barra caught this season in Tinaroo.Reads: 725