Enhancement of mulloway (Argyrosomus hololepidotus) in intermittently opening lagoons
Final report
Determination of ageing in kingfish (Seriola Ialandi) in NSW
Final report
Enhancement and farming of scallops in NSW using hatchery produced seedstock
Final report
This is a report on the second stage of a two part program investigating hatchery production, farming and seeding of the commercial scallop, Pecten fumatus. A total of more than four million scallop spat were produced for farming trials and over 250 000 scallops ranging in size from 20-60 mm were released into Jervis Bay.
Hatchery techniques were broadened to include procedures for the production of triploid P. fumatus. In general, the survival of triploid scallops was considerably lower than that of normal (diploid) scallops, particularly, immediately after treatment and during early larval rearing. No differences were observed between triploid and diploid spat, however, juvenile triploid scallops tended to be larger and heavier with significantly larger muscle tissues. The significant reduction in embryo development percentages (>80%), the relatively low percentage triploidy achieved initially (41%) followed by consistent reductions in percentage triploidy, mean that further research is required before it would be applied to the commercial sector.
Although our previous research had, for the first time, demonstrated reliable large scale rearing of P. fumatus larvae was possible, several major constraints to hatchery production were noted. Previously, larvae were either retained in the hatchery until they were large enough to be transferred to land based upweller systems, or larvae were settled on mesh in collector bags and transferred directly to the field. A new technique was developed in which larvae were settled on mesh screens held in the hatchery for about a fortnight before being placed in mesh bags at known densities and moved to the field for culture. This technique allows control of spat stocking density, and has produced threefold increases in spat yields over previous bag settlement techniques while significantly reducing maintenance costs.
KEYWORDS: Commercial scallop, hatchery production, farming, reseeding.
An assessment of the impact of offshore recreational fishing in NSW waters on the management of commercial fisheries
Final report
Conflict between the recreational and commercial sectors has long been a fisheries management problem. This conflict has been escalating in recent years as both sectors attempt to maximise catches. Consequently, there is increasing pressure being applied to fisheries managers to make appropriate allocation decisions regarding fishing opportunities for the various commercial and recreational user-groups. Accurate estimates of the magnitude of the recreational catch and fishing effort are required before any equitable allocation of resources among the commercial and recreational sectors can be made. Further, the acceptance of any management strategies by the general public and the various user-groups also requires that the calculations that underpin allocation decisions can be demonstrated to be sound and justified.
We have combined on-site surveys at large access sites with data obtained from a recreational boat movement logbook study to estimate the number of daytime recreational trailer boat fishing trips, and the number of daytime recreational cruiser and gameboat fishing trips, for all large sites that provide access for these types of boats to the marine waters of NSW. This same combination of on-site methods has also been used to estimate the day-time harvest of recreational trailer boat anglers, for all large sites that provide trailer boat access to the marine waters of NSW. We estimated that in excess of217,500 trailer boat trips were made from large access sites throughout the state during the first survey year (September 1993 to August 1994 inclusive) and more than 214,800 trips occurred during the second survey year (September 1994 to August 1995 inclusive). We estimated that in excess of 24,500 cruiser and gameboat trips were made from large access sites throughout the state during the first survey year (September 1993 to August 1994 inclusive) and more than 25,000 trips occurred during the second survey year (September 1994 to August 1995 inclusive).
We also conducted over 10,600 interviews with trailer boat angling parties during the two year period of the survey and found the retained catch of this marine recreational fishery to be extremely diverse. We recorded 210 taxa in the harvest statewide. Despite this diverse harvest, relatively few species accounted for the bulk of the recreational harvest, by weight and by number offish. The top ten species always accounted for more than 68% by number, and 59% by weight, of the recreational trailer boat harvest. This pattern of harvesting was consistent among regions and between survey years. The main species, by weight, during the first survey year were eastern blue-spotted flathead (229.3 tonnes), snapper (184.2 tonnes), silver trevally (103.5 tonnes), blue morwong (90.9 tonnes), yellowfin tuna (73. l tonnes), skipjack tuna (56.8 tonnes), kingfish (53.0 tonnes), silver sweep (47.5 tonnes), slimy mackerel (40.1 tonnes), and albacore (38.7 tonnes). The main species, by weight, during the second survey year were eastern blue-spotted flathead (207. 5 tonnes), snapper (18 7 .6 tonnes), silver trevally (112.3 tonnes), yellowfin tuna (59.1 tonnes), blue morwong (54.9 tonnes), silver sweep (43.2 tonnes), skipjack tuna (39.0 tonnes), kingfish (35.8 tonnes), albacore (35.1 tonnes), and sergeant baker (32.0 tonnes). Overall, recreational trailer boat harvests in excess of one tonne statewide were recorded for 55 taxa during the first survey year, and 54 taxa during the second survey year. Latitudinal differences in recreational harvest were evident for some species. For example, during both survey years the harvest of snapper was greatest in the northern region, intermediate in the central region and lowest in the southern region of the state.
We compared the estimates of daytime recreational harvest taken by trailer boat anglers in coastal waters to the declared commercial landings taken from NSW coastal waters. The recreational harvest was greater, or about the same as, the commercial catch for some species, such as eastern blue-spotted flathead, dolphin fish, cobia, blackspot pigfish, maori wrasse, dusky flathead and red scorpioncod. Conversely, the commercial catch was greater than the recreational daytime harvest for many other species such as snapper, mulloway, john dory, kingfish, blue morwong, nannygai , red gurnard, and silver trevally. We have documented great latitudinal changes in the harvesting patterns of many important species by both the recreational and commercial fisheries, which results in regional changes of harvest allocation between the sectors for these species. Examples include eastern blue-spotted flathead, snapper, tiger flathead, and silver trevally.
Sampling estuarine fish species for stock assessments
Final report
Estuarine fishes in NSW are exploited by commercial and recreational fishers and are subject to significant pressure from habitat degradation. The NSW commercial estuarine finfish fishery is highly complex as it is based on multi-species and many fishers using variety of methods. Furthermore, there is very little biological information on which to assess the status of these stocks. Four key species were identified for investigation: yellowfm bream (Acanthopagrns australis), sand whiting (Sillago ciliatd), dusky flathead (Platycephalus fuscus), and luderick (Girella tricnspidata).
Sampling of young (recently settled) juvenile fishes was used to assess recruitment variability in estuarine fishes. Quantitative sampling across several estuaries identified latitudinal gradients in the timing of recruitment of sand whiting, bream and luderick to estuarine habitats. The relative abundance of young fish varied greatly among sites within an estuary as well as between estuaries. Future sampling of juvenile fishes to obtain indices of recruitment would need to be done over extended periods of time and across many locations within an estuary and estuaries and would therefore be relatively costly.
Keywords: Estuarine fish, stock assessment, recruitment, size and age structure, log book, Sparidae, Sillaginidae, Platycephalidae, Girellidae
Restoration of estuarine fisheries habitat
Final report
NSW inland commercial fisheries analysis
Final report
The inland commercial fishery in New South Wales had a _mean annual catch of 344t over the past three decades, and is currently worth $1. 7 million per annum (1995/96 value). The commercial fishery commenced in the late 19th Century, and although production figures are available from 1883 onwards, coverage for years earlier than 1947 was very limited, with an unknown fraction of the total catch reported. The major species currently exploited by the fishery are golden perch, carp, Murray cod and freshwater yabby, while prior to 1980 redfin perch, silver perch and freshwater catfish were also significant components of the catch.
From the commencement of the commercial fishery there were resource conflicts between commercial fishers, traditional rights of the indigenous fishers, recreational fishers and a continual problem with widespread illegal fishing activities. The geographical extent of the fishery was gradually reduced to the current boundaries, which allow commercial fishing for finfish in approximately 5% of the linear measure of the inland waters of NSW.
There has been a long-established need for reliable data for the fishery, and while fishers have officially reported catches since 1947, the data have been poorly managed, and no comprehensive analysis has previously been attempted.