Age Structure Of The Commercial Catch Of Northern Territory Narrow-barred Spanish Mackerel
Funder
Fisheries Research and Development Corporation
Funding Amount
$18,662.00
Summary
Objectives: 1. Provide an estimated age structure for catches in the NT troll mackerel fishery for the 1991 to 1993 fishing seasons, for extension of population assessment to include an age-structured population model 2. Verify the growth relationships currently in use for stock assessment, or provide the information from which a new relationship might be developed
Investigation Of The Biology Of Tiger Prawns In The Western Gulf Of Carpentaria
Funder
Fisheries Research and Development Corporation
Summary
Objectives: 1. Detailed study of the 2 commercial tiger prawn species (Penaeus esculentus and P. semisculcatus) in Groote Eylandt region of northern prawn fishery: 2. population dynamics; spawning times & places; delimit nursery areas contribute to commercial stocks; recruitment
Developing Techniques To Estimate The Age Of Bigeye Tuna And Broadbill Swordfish Off Eastern Australia: A Pilot Project
Funder
Fisheries Research and Development Corporation
Funding Amount
$26,793.90
Summary
The BET and BBL swordfish fishery is expanding rapidly off the east coast of Australia and is now a significant fishery. The warning 'trigger', set by AFMA, of 800t of BBL caught this year has been exceeded. There is now an urgent need to gain an understanding of the stock structure of this fishery. There are now grave concerns, both within the Pacific and the Indian Ocean, on the possibility of over exploitation of these species.
Very little is known scientifically on these species (W ....The BET and BBL swordfish fishery is expanding rapidly off the east coast of Australia and is now a significant fishery. The warning 'trigger', set by AFMA, of 800t of BBL caught this year has been exceeded. There is now an urgent need to gain an understanding of the stock structure of this fishery. There are now grave concerns, both within the Pacific and the Indian Ocean, on the possibility of over exploitation of these species.
Very little is known scientifically on these species (Whitelaw and Unnithan. 1997). Critically there is no verifiable information on the size at maturity and age-structure of populations of BET and BBL in the western Pacific.
Stock assessments require knowledge of size at maturity, size at age, growth rate and estimates of the variability in these parameters within the stock.
For management plans to be devised and implemented it is necessary to expand our biological knowledge. A first step in a structured stock assessment of a fishery is to determine whether ages of individuals can be estimated from their bony parts (otoliths and spines). There is a need to develop verifiable age estimation techniques for stock assessment studies.
Refs; Whitelaw, A.W. and Unnithan, V.K. 1997. Synopsis of the distribution, biology and fisheries of the bigeye tuna, with a bibliography. CSIRO Marine Laboratories Report 228. 62pp. Objectives: 1. To collect hard parts (otoliths and spines) from broadbill swordfish and otoliths from bigeye tuna (much of this has been completed). 2. Assess a range of standard age estimation techniques using otoliths, vertebrate and spines of BET and BBL. This will be carried out in collaboration with SPC and NMFS. 3. Compare age estimates derived using these techniques with those of the SPC and NMFS using other techniques. 4. Using marked (strontium chloride) BET otoliths from previous SPC/CSIRO tagging studies, as well as tag release/recapture growth data from other tagging programs, attempt to validate our age estimation methods and techniques. 5. Make recommendations to Eastern Tuna MAC on the feasibility of an extended ageing project to provide biological information to stock assessment studies. Read moreRead less
Spawning And Reproductive Characteristics Of Bight Redfish And Deepwater Flathead In The Great Australian Bight Trawl Fishery
Funder
Fisheries Research and Development Corporation
Funding Amount
$89,975.00
Summary
Bight redfish (Centroberyx gerrardi) and deepwater flathead (Neoplatycephalus conatus) are the two principle commercial species captured along the continental shelf of the Commonwealth managed Great Australian Bight Trawl Fishery worth an estimated $7 million per annum.
Current assessments, based on available data, indicate that Bight redfish fishing mortality is rising and likely to reduce the biomass to below the trigger biological reference point. The outcomes of stock assessments ....Bight redfish (Centroberyx gerrardi) and deepwater flathead (Neoplatycephalus conatus) are the two principle commercial species captured along the continental shelf of the Commonwealth managed Great Australian Bight Trawl Fishery worth an estimated $7 million per annum.
Current assessments, based on available data, indicate that Bight redfish fishing mortality is rising and likely to reduce the biomass to below the trigger biological reference point. The outcomes of stock assessments are highly sensitive to the shape of the maturity ogive and fecundity-length/age relationships. Given the current high uncertainty about the validity of existing Bight redfish and deepwater maturity and fecundity relationships, GABFAG has recommended that these be determined with high priority. More scientifically defensible maturity ogives and fecundity-length and fecundity-age relationships will markedly reduce uncertainty in the stock assessments. Objectives: 1. Determine maturity ogives (against length/age) and sex ratios of spawning Bight redfish and deepwater flathead. 2. Describe gonad maturation cycles and determine the relationship between egg production (fecundity) and length/age in female Bight redfish and deepwater flathead 3. Conduct per recruit analysis to identify harvest strategies which allow optimum Bight redfish and deepwater flathead egg production (and therefore recruitment) 4. Provide Industry, GABMAC and stock assessment scientists with information on GABTF species biology. Read moreRead less
Objectives: 1. Determine optimal conditions for spawning, larval survival & spat settlement of Pacific oyster in Port Stephens 2. Strain numbers & seasonal distribution of Pacific & Sydney Rock oyster larvae 3. Distribution, abundance, age composition in NSW growing areas; seasonal gonad & meat; potential for QX & winter mortality resistance
Ageing Yellowtail (Trachurus Novazealandiae) And Blue Mackerel (Scomber Australasicus) In NSW
Funder
Fisheries Research and Development Corporation
Funding Amount
$68,287.00
Summary
Objectives: 1. To provide estimates of the size and age composition of the commercial and recreational harvest of yellowtail and blue mackerel 2. To provide provide preliminary validations of age estimates in these species 3. To provide estimates of geographic differences in the age composition of commercial and recreational catches
Tagging Of Southern Blue Fin Tuna Off The Coast Of Australia
Funder
Fisheries Research and Development Corporation
Summary
Objectives: 1. Evaluate yield-per-recruit with various harvesting. Update mortality information. Estimate abundance local exploited sub-populations. 2. Quantify information on age-specific migration patterns for simulation model. Technique for ageing SBT. 3. Structure & integrity of schools; exchange of fish among schools
Assessment Of Length And Age Composition Of Commercial Kingfish Landings
Funder
Fisheries Research and Development Corporation
Funding Amount
$142,101.00
Summary
Following a decision in 1990 to impose a minimum legal length of 60 cm (total length) on kingfish and the banning of pelagic traps in 1996, there has been considerable controversy concerning the appropriateness of the current management measures. Gillanders et al. (1997) demonstrated that the current minimum legal size is about 15 cm below the length at which 50% of females are mature. However, the absence of adequate size and age composition data for the commercial landings means it is not po ....Following a decision in 1990 to impose a minimum legal length of 60 cm (total length) on kingfish and the banning of pelagic traps in 1996, there has been considerable controversy concerning the appropriateness of the current management measures. Gillanders et al. (1997) demonstrated that the current minimum legal size is about 15 cm below the length at which 50% of females are mature. However, the absence of adequate size and age composition data for the commercial landings means it is not possible to determine the impact of possible changes in minimum legal size. Yield modelling, combined with information on composition of landings, is an appropriate and important first step in examining the suitability of minimum legal size settings. The nature of the commercial fishery for kingfish presents significant difficulties for the design of unbiased and cost effective sampling of these fisheries. Kingfish are caught in significant quantities in small, localised fishing operations, mainly south of 30° S latitude. There appears to be considerable annual and seasonal variation in the catches by the various sectors, however it is known that when reasonable densities of kingfish are located, very high catches can be taken over short time periods. The dispersed yet intense nature of the fishery has great potential to cause bias in collections aimed at estimating the length and age composition of the total catch of kingfish. A major aim of this proposal is to develop cost effective sampling strategies which will minimise bias in ongoing monitoring of the kingfish fishery. The collection of size and age composition estimates from the commercial catch will enable the evaluation of whether an age structured model would be an appropriate mechanism for assessing the status of the fishery. Variation in the relative strength of year classes can be evaluated in each of the three years and these will provide important information on the dynamics of this stock. Further, these data can be used to provide auxiliary inputs for the fitting of a synthetic model which will utilise catch-effort data that have been collected from the fishery. Objectives: 1. To accurately document the size and age composition of kingfish landed by commercial fishers in NSW. 2. To refine existing estimates of kingfish growth with new information on size at age, with a focus on large fish. 3. To examine the suitability of the current minimum legal length with yield models, utilising the improved information on kingfish growth and information on kingfish size and age composition. 4. To examine the possibility of using age-structured modelling in future assessments of yellowtail kingfish. Read moreRead less
Objectives: 1. Determine whether scallop settlement has occurred on the major beds adjacent to Lakes Entrance 2. Determine the time interval between settlement and recruitment
Description Of The Biology And An Assessment Of The Fishery For Silver Trevally Off NSW
Funder
Fisheries Research and Development Corporation
Funding Amount
$108,390.00
Summary
Because of the increasing significance of silver trevally to a number of fisheries off NSW (including the trawl sector of the SEF, where it is one of 16 species managed by Total Allowable Catch) and the current lack of data on which to assess the impact of fishing on the stock, it is important to undertake research which will lead to an understanding of the current status of the stock.
There is a need to determine the basic biological parameters, including growth rates and spawning bio ....Because of the increasing significance of silver trevally to a number of fisheries off NSW (including the trawl sector of the SEF, where it is one of 16 species managed by Total Allowable Catch) and the current lack of data on which to assess the impact of fishing on the stock, it is important to undertake research which will lead to an understanding of the current status of the stock.
There is a need to determine the basic biological parameters, including growth rates and spawning biology for use in stock assessment modeling.
In order to provide the data necessary to adequately assess the status of the trevally stock, there is a need to document the portion of the stock utilised by the various fishery sectors, and to determine the relative impacts on the stock of each sector. It is also important that a monitoring regime be established which will provide data on which to base advice for the future sustainable management of exploitation of the resource. Objectives: 1. The first objective of this research program is to describe the size and age composition of the catch of silver trevally taken by each of the sectors utilising the resource in waters off NSW.. 2. The reproductive biology of the species will also be investigated, including determination of the size at first maturity, spawning period and fecundity. 3. Techniques to age silver trevally will be refined and applied to samples from both commercial and recreational catches following which a growth rate model for this species in NSW will be developed. 4. All relevant data will be incorporated in an initial stock assessment which will describe the relative impact on the silver trevally stock of the various fishery sectors. 5. Advice will be provided to fishery managers on the status of the stock, and the appropriateness or otherwise of establishing a minimum legal size for silver trevally. Read moreRead less