Thor Saunders

Northern Territory Department of Primary Industry and Resources,Darwin, Australia

Failure to consider population structure when managing harvested fishes increases the risk of stock depletion, yet empirical estimates of population structure are often lacking for important fishery species. In this study, we characterise genetic variation in single nucleotide polymorphisms (SNPs) to assess population structure for three harvested...

Australia’s fisheries have experience in responding individually to specific shocks to stock levels (for example, marine heatwaves, floods) and markets (for example, global financial crisis, food safety access barriers). The COVID-19 pandemic was, however, novel in triggering a series of systemic shocks and disruptions to the activities and operati...

Trait‐based models of ecological communities and ecosystem functioning often fail to account for intraspecific variation in functional traits, assuming that intraspecific variability is negligible compared with interspecific variability. However, this assumption remains poorly tested across vertebrate animals where past studies routinely describe s...

Fisheries and natural water resources across the world are under increasing pressure from human activity, including fishing and irrigated agriculture. There is an urgent need for information on the climatic/hydrologic drivers of fishery productivity that can be readily applied to management. We use a generalized linear mixed model framework of catc...

Mercury distribution and bioaccumulation in aquatic ecosystems of tropical Australia is poorly characterised. Barramundi (Lates calcarifer), a widespread high-order predator in both fresh and coastal marine waters of the region, fulfils requirements for a bio-indicator of mercury contamination. In a study of the Mary River system of the Northern Te...

Understanding population structure is important for predicting the outcomes of anthropogenic development, harvest, and environmental change on the abundance of fisheries species. Logically, the use of several data sources is best for delineating population structure, but combining across data types adds extra challenges as results can be incongruen...

We describe a first estimate of the potential to increase production from Australia’s commercial fisheries based on the difference between current catches and maximum sustainable yield (MSY). MSY is not being advocated as a target reference point but enables a level of consistency across species and/or jurisdictions with different reference points....

The relationship between growth and sexual maturation is central to understanding the dynamics of animal populations which exhibit indeterminate growth. In sequential hermaphrodites, which undergo post-maturation sex change, the size and age at which sex change occurs directly affects reproductive output and hence population productivity. However,...

With recent advances in sequencing technology, genomic data are changing how important conservation management decisions are made. Applications such as Close‐Kin Mark‐Recapture demand large amounts of data to estimate population size and structure, and their full potential can only be realised through ongoing improvements in genotyping strategies....

The Black jewfish (Protonibea diacanthus) is a large-bodied species of croaker that is highly prized for its table qualities. Black jewfish are aggregative in behaviour, making them a key focus of all stakeholders in the Northern Territory. They have been heavily overfished across their tropical Indo-West Pacific distribution with northern Australi...

Natural river floodplains are among the Earth's most biologically diverse and productive ecosystems but face a range of critical threats due to human disturbance. Understanding the ecological processes that support biodiversity and productivity in floodplain rivers is essential for their future protection and rehabilitation. Fish assemblage structu...

In gape-limited predators, gape size restricts the maximum prey size a predator is capable to ingest. However, studies investigating the energetic consequences of this relationship remain scarce. In this study, we tested the hypothesis that gape-size variability influences individual body condition (a common proxy for fitness) in one of the largest...

Diadromy is a form of migration where aquatic organisms undergo regular movements between fresh and marine waters for the purposes of feeding and reproduction. Despite having arisen in independent lineages of fish, gastropod molluscs and crustaceans, the evolutionary drivers of diadromous migration remain contentious. We test a key aspect of the ‘p...

Species traits are a new data currency to enhance our understanding of ecological patterns and processes. Trait‐based studies of fishes are numerous in comparison with other animal groups, reflecting the diversity of fish forms and functions they provide to aquatic ecosystems. We conduct a retrospective examination of literature to identify knowled...

A fundamental characteristic of calcified structures commonly used for direct age estimation in animals is that new material is accreted cumulatively and preserved across ontogeny, thus allowing growth marks to be reliably observed and counted. Direct age estimation in crustaceans has been problematic due to molting of calcified structures across o...

The grass emperor Lethrinus laticaudis is a conspicuous element of the commercial and recreational catch from nearshore reef systems across northern Australia. The nearshore reef systems across northern Australia are exposed to increasing levels of fishing pressure from commercial and recreational fishers. To inform ongoing management of this speci...

Understanding the drivers of dispersal among populations is a central topic in marine ecology and fundamental for spatially explicit management of marine resources. The extensive coast of Northwestern Australia provides an emerging frontier for implementing new genomic tools to comparatively identify patterns of dispersal across diverse and extreme...

As pressure on coastal marine resources is increasing globally, the need to quantitatively assess vulnerable fish stocks is crucial in order to avoid the ecological consequences of stock depletions. Species of Sciaenidae (croakers, drums) are important components of tropical and temperate fisheries and are especially vulnerable to exploitation. The...

Involving Indigenous community members to assist with the monitoring of harvested populations can greatly assist with the sustainable use of these resources. The benefits of training Indigenous community members in western scientific methods include: increased capability development, increased employment opportunities and more cost effective monito...

Modeling fisheries populations is one of the many components of management aimed at achieving sustainable exploitation. Definition of the spatial extent of stocks, in particular, is a founding principle of this assessment process. The concept of stocks as natural management units is based on demographically cohesive groups of individuals of a speci...

The integrated use of a number of techniques that cover multiple aspects of a fish species' life history have been shown to provide the best basis for potential management of that species. Parasites provide information on aspects of short- to long-term aspects of a fish's biology, depending on the parasite species in question. In this study, the pa...

Information on the structure of exploited fish populations is critical to their sustainable harvest, allowing appropriate management regimes to be implemented at spatial scales that reflect the population dynamics of a species across it range. This project utilised microsatellite DNA, parasitology and otolith microchemistry techniques to examine po...

Thirty-four microsatellite loci were isolated from three reef fish species; golden snapper Lutjanus johnii, blackspotted croaker Protonibea diacanthus and grass emperor Lethri-nus laticaudis using a next generation sequencing approach. Both IonTorrent single reads and Illumina MiSeq paired-end reads were used, with the latter demonstrating a higher...

Creating large conservation zones in remote areas, with less intense stakeholder overlap and limited environmental information, requires periodic review to ensure zonation mitigates primary threats and fill gaps in representation, while achieving conservation targets. Follow-up reviews can utilise improved methods and data, potentially identifying...

The grass emperor Lethrinus laticaudis is a coral reef fish that has high value to fisheries and is vulnerable to overharvesting. The complete mitochondrial genome was assembled from approximately 5.5 million reads produced by Illumina MiSeq. The 16,758 bp consisted of 13 protein-coding genes, 22 transfer RNA genes and two ribosomal RNA genes (12S...

Australian marine wild-capture fisheries are managed by eight separate jurisdictions. Traditionally, fishery status reports have been produced separately by most of these jurisdictions, assessing the fish stocks they manage, and reporting on the effectiveness of their fisheries management. However, the format, the type of stock status assessments,...

Migration is a fundamental aspect of the life history of many fish and must be well understood for targeted conservation and management. We used acoustic telemetry and otolith ⁸⁷Sr/⁸⁶Sr analysis, in conjunction with annual ageing, to study intraspecific variation in barramundi Lates calcarifer migration in the Northern Territory, Australia. Acousti...

The national reporting framework used in the Status of key Australian fish stocks reports 2014 was developed collaboratively by fisheries scientists from around Australia. This framework uses standardised terminology and reference points for stock status classifications. Following release of the Status of key Australian fish stocks reports 2012, a...

Abstract We describe the complete mitochondrial genome of the golden snapper Lutjanus johnii. It was assembled from approximately 1.4 million reads produced by Ion Torrent next generation sequencing. The complete genome was 16,596 bp in length consisting of 13 protein-coding regions, 22 tRNA, 12S and 16S rRNA as well as two non-coding regions. The...

Abstract We describe the complete mitochondrial genome of the black Jewfish Protonibea diacanthus. It was assembled from approximately 1.6 million reads produced by Ion Torrent next generation sequencing. The complete genome was 16,521 bp in length consisting of 13 protein-coding regions, 22 tRNA, 12S and 16S rRNA as well as two non-coding regions....

In total, 150 stock status assessments were undertaken across the 49 species chapters, with assessments undertaken at the biological stock level, wherever possible. A stock status classification could be determined from 111 of the stocks assessed. The remaining 39 were classified as undefined stocks. The undefined stock classification does not nece...

Abstract  Stable isotopes of δ18O and δ13C in sagittal otolith carbonates were used to determine the stock structure of the polynemid Eleutheronema tetradactylum (Shaw) across tropical northern Australia, where this species is an important component of inshore commercial and recreational fisheries. Stable isotopes from the sagittal otolith carbonat...

Otoliths of king threadfin, Polydactylus macrochir were collected from 2007 to 2009 at nine locations across northern Australia representing most of their distributional range and areas where fisheries are active. Measurement of the stable isotope ratios of δ18O and δ13C in the sagittal otolith carbonate from assemblages of P. macrochir revealed lo...

Many species of sedentary marine invertebrates exhibit large spatial variation in their morphology, which allow them to occupy a broad geographic distribution and range of environmental conditions. However, the detection of differences in morphology amongst variable environments cannot determine whether these differences represent a plastic respons...

Saunders, T., Mayfield, S., and Hogg, A. 2009. Using a simple morphometric marker to identify spatial units for abalone fishery management. – ICES Journal of Marine Science, 66: 305–314. Managing stocks of sedentary marine invertebrates is complicated by the highly structured populations they form. Blacklip abalone (Haliotis rubra) form isolated po...

Many sedentary marine invertebrates have a fine-scale (100s m) population structure that complicates their conservation and management. This is a consequence of the limited information on the boundaries between component populations and the biological variability among them. Blacklip abalone Haliotis rubra form discrete populations, many of which a...

Abalone surveys worldwide measure relative stock abundance. However, important advantages accrue if diver surveys measure absolute numbers or biomass per square metre. Principally, absolute biomass permits quota setting from a single survey using a decision table. Although relative abundance surveys have permanently fixed sampling protocols and loc...

Discarded by-catch in prawn fisheries is likely to affect trophic balance including the population structure and function of both the exploited species and scavengers on discards. The Spencer Gulf prawn fishery consists of 39 trawlers operating about 60 days a year with a management system allowing large differences in spatial effort. Such a system...

The ability to identify and separately manage component populations is becoming increasingly important in guarding against overexploitation of many marine species. Blacklip abalone (Haliotis rubra) form isolated populations with variable life history characteristics as a result of the heterogenous areas they inhabit. Many of these populations are '...

A two-chambered lobster trap was developed that in aquarium trials significantly (p < 0.01) reduced octopus predation on trap-caught spiny lobster. The trap was designed using information gained from an investigation of the behavioural interactions of the maori octopus (Octopus maorum) with traps used in the South Australian commercial lobster (Jas...

Octopus are common bycatch species in many commercial fisheries for southern rock lobster (Jasus edwardsii). In these fisheries, octopus predation on lobsters caught in traps is a significant cause of lobster mortality. In the South Australian commercial fishery for southern rock lobster ∼4% of the total annual catch is killed by the maori octopus...