Resource monitoring of the jack mackerel purse seining fishery in south-eastern Australia
Final report
This program has collected data on the development and performance of the fishery, as well as biological data relevant to assessment of the impact of fishing on the exploited population.
The development and operation of the fishing and processing sectors of the fishery are described as are the development and implementation of jack mackerel management in Tasmania.
Biological data presented for jack mackerel include size structure of catch, length-weight relationships, catch age structure and reproductive development Estimates for the Von Bertalanffy parameters L∞, K and t0 are resented. Problems encountered estimating mortality rates are discussed and preliminary estimates given.
The bycatch species redbait, Emmelichthys nitidus, and blue mackerel, Scomber australasicus, make up approximately 5% of the landed catch. Some biological information on these two species is also presented.
The discovery of several adult Peruvian jack mackerel Trachurus murphyi raises questions as to the importance of this species, if any, in the fishery. These samples constitute the most westerly reports of this species distribution.
The importance of inter-annual variability in this fishery is discussed with reference to examples in the short history of the fishery.
Development of inshore ring netting techniques for the capture of squid and jack mackerel
Assessment of optimal trapping techniques to control densities of northern Pacific seastars on marine farm leases
Feasibility study of the application of satellite remote sensing to fisheries investigations
Final report
Assessment of demersal fish resources of the south western sector
The development of an index for the prediction of catches of blacklip and greenlip abalone, and a technique for ageing these species
Final report
The scientific literature has generally accepted that abalone populations are characterised by low levels of settlement and recruitment (Tegner in press), that mortality is relatively low (Doi et al. 1977; Beinssen and Powell 1979; Sainsbury 1982; Shepherd et al. 1982; Fournier and Breen 1983) and uniform throughout life (Shepherd et al. 1982), and correspondingly that the natural productivity of these stocks is low (Tegner in press). In some studies it has been noted that one or more year classes are apparently missing (Forster et al. 1982; Sainsbury 1982) and this has led to the conclusion that abalone recruitment is relatively sporadic and irregular. It has been generally assumed that larval dispersal is relatively widespread (20-50km; Tegner & Butler 1985). No relationship had been observed between the abundance of breeding stock and the abundance of recruitment. On the basis of these observations and laboratory studies, together with genera lly held assumptions, it has been accepted that oceanographic and other environmental factors would be the major determinants of settlement and recruitment density (Fedorenko & Spout 1982; Tegner in press).
It was these widely held views which led to the original rationale for this project, which was to develop an index of settlement or recruitment abundance which could be used to predict broad scale trends in the future abundance of the fishable stock.
In addition, there was also no scientifically proven method of ageing abalone prior to this study, and it was generally accepted that the Australian species of abalone could not be aged. The FIRTA-funded review of Ward (1986) found that this was a major impediment of research into and assessment of abalone stocks in Australia.