Jonathan Mitchell

Queensland Government · Department of Agriculture and Fisheries

Fisher-shark conflict is occurring at Lord Howe Island, Australia due to high levels of Galapagos shark (Carcharhinus galapagensis) depredation (where sharks consume hooked fish) and bycatch. Depredation causes costly loss of target catch and fishing gear and increased mortality of target species, and sharks can be injured or killed when bycaught....

Context Coastal beach environments provide habitats for marine megafauna, including turtles, rays, marine mammals and sharks. However, accessing these variable energy zones has been difficult for researchers by using traditional methods. Aims This study used drone-based aerial surveys to assess spatio-temporal variation of marine megafauna across s...

The black jewfish (Protonibea diacanthus) occurs in tropical coastal waters throughout the central Indo-Pacific. It has long been valued as an important recreational and artisanal fishery species but has become increasingly targeted by commercial fisheries due to demand for its large swim bladder. To better understand how changes in fishing pressur...

Tag-recapture programs to monitor the movements of fish populations are among some of the longest-running citizen-science datasets to date. Here, using half a century of yellowtail kingfish (Seriola lalandi, Carangidae) tag-recapture data collected through citizen-science projects, we report novel insights into population connectivity in Australia...

Background Acoustic telemetry has become a fundamental tool to monitor the movement of aquatic species. Advances in technology, in particular the development of batteries with lives of > 10 years, have increased our ability to track the long-term movement patterns of many species. However, logistics and financial constraints often dictate the locat...

Shark depredation is a complex social-ecological issue that affects a range of fisheries worldwide. Increasing concern about the impacts of shark depredation, and how it intersects with the broader context of fisheries management, has driven recent research in this area, especially in Australia and the United States. This review synthesises these r...

Drones enable the monitoring for sharks in real-time, enhancing the safety of ocean users with minimal impact on marine life. Yet, the effectiveness of drones for detecting sharks (especially potentially dangerous sharks; i.e., white shark, tiger shark, bull shark) has not yet been tested at Queensland beaches. To determine effectiveness, it is nec...

We developed and applied a method to quantify spearfisher effort and catch, shark interac- tions and shark depredation in a boat-based recreational spearfishing competition in the Great Barrier Reef Marine Park in Queensland. Survey questions were designed to collect targeted quantitative data whilst minimising the survey burden of spearfishers. We...

This report presents the results of the Queensland SharkSmart Drone Trial, which ran from Sept 2020 - Oct 2021. The results include the number of shark sightings, the influence of environmental and operational factors on the ability of drones to detect sharks and a comparison of shark sightings vs catch in shark control nets and drumlines. The repo...

The highly migratory Blue Shark, Prionace glauca is a seasonal migrant to waters to the southwest of England, where it can be locally abundant. The Pat Smith database, representing a collaboration between recreational anglers and scientists, currently records 99,511 P. glauca catch and release captures by recreational anglers from 1953 to 2019. The...

Shark depredation, whereby hooked fish are partially or completely consumed before they can be retrieved, occurs globally in commercial and recreational fisheries. Depredation can damage fishing gear, injure sharks, cause additional mortality to targeted fish species and result in economic losses to fishers. Knowledge of the mechanisms behind depre...

Located ~600km offshore from the New South Wales coast, the State and Commonwealth marine parks surrounding Lord Howe Island support the world’s most southerly coral reef, are renowned for their biodiversity, and offer unique opportunities for tourism and recreational activities, including fishing. The Galapagos shark (Carcharhinus galapagensis) is...

Results from analysis of the Southwest of England recreational blue shark fishery from 1998-2019 are presented for the purpose of the 2020 ICCAT request for data on the species. During this period 22287 Blue Sharks were captured during 44776.5 hours fished, giving an overall CPUE of 0.497 fish/hour. CPUE varied between 0.036-0.173 during 1998-2009,...

The volume of the olfactory bulbs relative to the brain has been used previously as a proxy for olfactory capabilities in many vertebrate taxa, including fishes. Although this gross approach has predictive power, a more accurate assessment of the number of afferent olfactory inputs and the convergence of this information at the level of the telence...

Baited video systems have been widely used to assess the relative abundance and diversity of sharks in locations around the world, however they provide limited information on behaviour. We developed and pilot tested a novel experimental approach to investigate whether repeated deployments of baited video systems in the same location could generate...

Shark depredation, whereby a shark consumes an animal caught by fishing gear, can cause higher mortality for target species, injury to sharks and the loss of catch and fishing gear. A critical first step towards potential mitigation is understanding this behaviour and the shark species involved, because the identity of depredating shark species is...

Shark depredation, where a shark partially or completely consumes an animal caught by fishing gear before it can be retrieved to the fishing vessel, occurs in commercial and recreational fisheries worldwide, causing a range of negative biological and economic impacts. Despite this, it remains relatively understudied compared to other fisheries issu...

Shark depredation, where a shark consumes a hooked fish before it can be retrieved to the fishing vessel, can occur in recreational fisheries. This may cause higher mortality rates in target fish species, injuries to sharks from fishing gear and negatively impact the recreational fishing experience. This study quantified spatial variation and frequ...

The effect of environmental variables on blue shark Prionace glauca catch per unit effort (CPUE) in a recreational fishery in the western English Channel, between June and September 1998-2011, was quantified using generalized additive models (GAMs). Sea surface temperature (SST) explained 1·4% of GAM deviance, and highest CPUE occurred at 16·7° C,...

The North Atlantic blue shark (Prionace glauca) population has declined significantly in recent decades, due to increasing fishing pressure driven by demand for fins. This highlights the need for greater understanding of P. glauca biology and ecology, and its interaction with fisheries, to prevent further declines. This research quantified the impa...