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1. It directly addresses a NT RAC priority in the 2019 call for funding applications relating to improving sustainable yield estimates to inform stock assessment programs for undefined target species and protected species in the Offshore Net and Line Fishery. The project will support sustainable fishing practices for important commercial fisheries in the NT and the development of new commercial opportunities within these fisheries: The impacts of fishery activities on these species, either through bycatch or targeted harvest, are difficult to assess in the absence of information on population connectivity and stock structure.

2. The project will develop capacity for fisheries research and monitoring in NT waters. Genetics methods are widely applied to fisheries research and monitoring and training of an early career fisheries scientist in the application and interpretation of genetic data will be a key outcome of this project.

3. The project will provide key information to support the transition of these species from bycatch to a harvested byproduct species, including an evaluation of leading-edge genetic techniques in fisheries assessment and monitoring.

Objectives

1. To develop population connectivity model for Whitecheek and Milk Shark

2. To develop capacity for research and monitoring of shark species within the Northern Territory

3. To evaluate the utility of genetic techniques in fisheries monitoring

Final report

ISBN: 978-1-922684-78-3 (Print), 978-1-922684-79-0 (Web)

Authors: Sam Banks Amy Kirke Fernanda Alves Grant Johnson and David Crook

Final Report • 2024-10-01 • 1.08 MB

2020-036-DLD.pdf

Summary

Charles Darwin University and the Northern Territory (NT) Department of Industry, Tourism and Trade (DITT) Fisheries Division used genetic data to investigate the population structure of two small tropical shark species (Milk Shark [Rhizoprionodon acutus] and Australian Blackspot Shark [Carcharhinus coatesi]), which are caught as bycatch from commercial fisheries in the NT.

The aim of this study was to gain information on the genetic stock structure to inform the future management of these two species in the NT. This project was conducted in parallel with a PhD project investigating the biology and ecology of both species for applications to fisheries management. There is motivation by the NT Government to develop these two shark species into a commercial product. This project used genetic analysis to understand the patterns of connectivity of populations of these two shark species in NT waters and adjacent regions, including northern Western Australia and Papua New Guinea.

These two shark species that are captured as bycatch in the NT Demersal Fishery have the potential to be developed into a byproduct to add value to that fishery. A sustainable commercial harvest of these two species could greatly reduce the waste from fisheries, where they are currently abundant and caught in relatively large numbers. We address current knowledge gaps in biological information about populations of R. acutus and C. coatesi to inform the potential development of a byproduct fishery for these two species in the NT.

Genetic data from R. acutus and C. coatesi strongly suggest that each species exists as a single, highly connected population in the NT. Genetic differentiation among the sampling locations for each species was low, and genetic clustering analyses provided strong support for a single population of each species in the region. Sharks of both species captured within a single location (within 50 km of one another) were more genetically related than those further apart; however, this does not constitute evidence for multiple, spatially discrete populations of either species in NT waters. Preliminary applications of effective population size estimators were used, but further work is needed to determine if these can be used to indicate trends in abundance.

The immediate implications of our research are for fisheries scientists and managers. Our results indicate that these two shark species can be monitored and managed in the NT under the assumption that each species occurs as a single population in this region. Parasite and vertebral chemistry data collected as part of a PhD project conducted in parallel with this project suggest that, for C. coatesi, individuals may be resident within certain regions (eastern versus western NT waters) but the genetic data collected here suggest that, on a generational timescale, both species occur as highly-connected populations across in the NT region.

Our research has potential implications for commercial fishers, particularly from the NT Demersal Fishery. The information from our research will flow through to the industry by contributing to the information required to develop a byproduct fishery for the two species, by utilising bycatch and increasing economic return.

PROJECT NUMBER • 2019-212

PROJECT STATUS:

COMPLETED

Compilation of information for the US Marine Mammal Protection Act Comparability Finding process

Recent changes to legislation in the United States (US) requires that nations importing seafood must demonstrate that they have a regulatory program for reducing marine mammal bycatch that is comparable in effectiveness to the US standards under the ‘Fish and Fish Product Import...

ORGANISATION:

Alice Ilona Mackay

TAGS

Resource Rehabilitation

PROJECT NUMBER • 2019-013

PROJECT STATUS:

COMPLETED

Modelling environmental changes and effects on wild-caught species in Queensland

This project studied environmental factors which may be influencing the recruitment, catchability or productivity of Snapper, Pearl Perch, and Spanner Crab stocks in Queensland. Two environmental variables: GSLA and Chl-a were found to have strong associations with either abundance or catchability...

ORGANISATION:

University of Queensland (UQ)

TAGS

SPECIES

PROJECT NUMBER • 2017-094

PROJECT STATUS:

COMPLETED

NCCP: Review of Carp control via commercial exploitation

The present study, undertaken by Charles Sturt University, was developed to investigate the potential for commercial, or subsidised, fishery exploitation to effectively control carp populations in Australia. Using published literature examples of fish (and other) vertebrate pest-removal...

ORGANISATION:

La Trobe University Mildura Campus

TAGS

SPECIES

PROJECT NUMBER • 2018-034

PROJECT STATUS:

COMPLETED

Effects of climate change and habitat degradation on Coral Trout

Fishes are at considerable risk from changing environmental conditions because they are, for most part, unable to regulate their body temperature. Exposure to high temperatures may therefore compromise critical biological functions, resulting in reduced performance, fitness and ultimately survival....

ORGANISATION:

James Cook University (JCU)

TAGS

SPECIES

PROJECT NUMBER • 2019-103

PROJECT STATUS:

COMPLETED

Strategic Planning Workshop for Yellowtail Kingfish Stock Assessment in South-Eastern Australia

The project facilitated cross-jurisdictional and cross-sectoral discussions on aspects of the Eastern Australia biological stock of Yellowtail Kingfish. Several knowledge gaps relating to biological and life-history parameters, as well as reliable data on the recreational fishery across all...

ORGANISATION:

Department of Primary Industries and Regional Development (NSW)

TAGS

Tagging

Stock Assessment

Resource Rehabilitation

Recreational Fishing

Rac Vic

SPECIES

Yellowtail Kingfish

PROJECT NUMBER • 2018-067

PROJECT STATUS:

COMPLETED

Socio-economic characterisation of a small scale commercial fishery: opportunities to improve viability and profitability in the Tasmanian Scalefish Fishery

ORGANISATION:

University of Tasmania (UTAS)

TAGS

SPECIES

PROJECT NUMBER • 2016-009

PROJECT STATUS:

COMPLETED

Aquatic Animal Health and Biosecurity Subprogram: Perkinsus olseni in abalone - development of fit-for-purpose tools to support its management

The project was able to successfully propagate a new P. olseni isolate from Queensland and successfully cultured the isolates from Spain, Japan, New Zealand, and South Australia as well as P. chesapeaki, which was used as a negative control. We were unable to culture the Western Australian (WA)...

ORGANISATION:

Department of Primary Industries and Regional Development (DPIRD) WA

TAGS

SPECIES