David J. Welch

C2O Fisheries · www.c2ofisheries.net.au

Traditionally, small island communities around the world have had a strong association with their marine resources, depending on small-scale fisheries for food security, livelihoods, cultural practices and economic and rural development. This reliance on marine resources stems from having access to large ocean areas and therefore small islands are...

Patterns of age and growth of a sedentary damsel fish Acanthochromis polyacanthus were tested over a latitudinal range of approximately 10 degrees (1200 km) on the Great Barrier Reef (GBR), Australia. Within latitudes, these patterns were also compared on reefs in distance strata (inner, mid, and outer) across a continental shelf that ranged in wid...

Patterns of age and growth of a sedentary damsel fish Acanthochromis polyacanthus were tested over a latitudinal range of approximately 10 degrees (1,200 km) on the Great Barrier Reef, Australia. Within latitudes these patterns were also compared on reefs across a continental shelf that ranged in width from 52 to 128 km. Although variation in lengt...

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...

The region of eastern Australia covers a vast coastline that supports many different fisheries of cultural, economic and social importance. This vast area covers a large range in climate and climate variability and this chapter provides a synthesis of these through case studies of some of the most important fishery species. Reflecting the status of...

Sharks, rays, and chimaeras (Class Chondrichthyes; herein ‘sharks’) are the earliest extant jawed vertebrates and exhibit some of the greatest functional diversity of all vertebrates. Ecologically, they influence energy transfer vertically through trophic levels and sometimes trophic cascades via direct consumption and predation risk. Through movem...

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...

Fishing pressure is a significant driver of the demography of exploited fish populations. Here, we examine temporal patterns in the demography of king threadfin ( Polydactylus macrochir ), a large, protandrous teleost, in Queensland’s south-eastern Gulf of Carpentaria, Australia, between two periods: 1986–1990 (Period 1) and 2007–2009 (Period 2). S...

Global climate change is increasingly considered one of the major threats to tropical coastal fisheries, potentially undermining important revenue and food security provided by coral reef ecosystems. While there has been significant and increasing work on understanding specific effects of climate change on coral reef fishes, few studies have consid...

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...

No universally accepted code of practice or conduct exists for the practice and management of recreational fisheries (Cowx and Arlinghaus 2008). In Australia, a national code of practice for recreational and sport fishing was identified as a need in the 1994 National Recreational Fishing Policy. In 1995, state government, recreational fishers and p...

Coral grouper (genus Plectropomus), or coral trout, are members of the grouper family (Epinephelidae) and are one of the largest and most conspicuous predatory fishes on Indo-Pacific coral reefs. They are highly-prized food fishes that are targeted by subsistence, artisanal, commercial and recreational fisheries throughout their geographic range. P...

Climate change impacts on marine fisheries are being observed in tropical regions, including northern Australia and the Pacific. In the Torres Strait, Islanders have a long association with their sea country that holds significant cultural, social and economic importance. Future impacts of climate change on marine fisheries stocks and supporting ha...

The Global Strategy for the Conservation of Sharks and Rays (2015–2025), summarized here, is the product of an intensive 18-month strategic planning process incorporating extensive data analysis and synthesis, including a set of background documents, several technical workshops, and ongoing consultation and review. This process involved a team of e...

ABSTRACT: Physical barriers can have profound impacts on dispersal in marine species. Here, we investigate population structure and levels of relatedness among individuals of the coral reef associated fish, the dogtooth tuna Gymnosarda unicolor , collected from 15 sites across the Indo-West Pacific region. We screened 92 individuals for genetic var...

A plain-language summary of the eleven past, present and emerging themes in which genetic technology can assist in the maintenance of productive and sustainable harvesting.

We describe the isolation and development of 13 polymorphic microsatellite loci for the reef-associated dogtooth tuna Gymnosarda unicolor (Perciformes: Scombridae). The loci were tested on 20 individuals from a single population at Flinders Reef, located off the east coast of Australia. No evidence of linkage disequilibrium was detected between any...

Significant changes have occurred in the well-established partnership between fisheries managers and geneticists over the last 50 years. It is therefore timely to review and recalibrate the ways in which genetic technologies can assist the fishing industry to maintain productive and sustainable harvests. Our objective is to contribute to the mutual...

Climate change is considered to be a major environmental threat and there is a national priority to better establish the likely effects of climate change on Australia’s fisheries. Positive and negative impacts of climate change on marine fisheries are already being observed in tropical regions, including the GBR and Pacific. In the Torres Strait re...

Using mitochondrial DNA for species identification and population studies assumes that the genome is maternally inherited, circular, located in the cytoplasm and lacks recombination. This study explores the mitochondrial genomes of three anomalous mackerel. Complete mitochondrial genome sequencing plus nuclear microsatellite genotyping of these fis...

Life-history characteristics of six tropical Lethrinus species sampled from the Great Barrier Reef World Heritage Area were compared. Two species groups were identified based on fork length (LF ): large species with maximum LF > 640 mm (longface emperor Lethrinus olivaceus, yellowlip emperor Lethrinus xanthochilus and spangled emperor Lethrinus neb...

A plain-language summary of the eleven past, present and emerging themes in which genetic technology can assist in the maintenance of productive and sustainable harvesting.

Climate change is considered to be a major environmental threat and there is a national priority to better establish the likely effects of climate change on Australia’s fisheries. Positive and negative impacts of climate change on marine fisheries are already being observed in tropical regions, including the GBR and Pacific. In the Torres Strait re...

Precaudal vertebral counts were used to distinguish between 237 morphologically similar Carcharhinus limbatus and Carcharhinus tilstoni and were congruent with differences in reproductive ecology between the species. In addition to differing lengths at maturity and adult body size, the two species had asynchronous parturition, were born at differen...

Understanding the life history of exploited fish species is not only critical in developing stock assessments and productivity models, but has a dual function in the delineation of connectivity and geographical population structure. In this study, patterns in growth and length and age at sex change of Polydactylus macrochir, an ecologically and eco...

Temporal and spatial patterns in parasite assemblages were examined to evaluate the degree of movement and connectivity of post-recruitment life-history stages of a large, non-diadromous tropical estuarine teleost, king threadfin Polydactylus macrochir, collected from 18 locations across northern Australia. Ten parasites types (juvenile stages of t...

Life history characteristics were used to determine the stock structure of the polynemid Eleutheronema tetradactylum across northern Australia. Growth, estimated from back-calculated length-at-age from sagittal otoliths, and length at sex change were estimated from samples collected from 12 different locations across western, northern and eastern A...

Interspecies hybridisation in nature is a well-studied phenomenon, but it has not been analysed using genetic markers in the class Chondrichthyes (sharks, rays and chimeras). Two black-tip whaler shark species (Australian, Carcharhinus tilstoni; Common, C. limbatus) have overlapping distributions in Australia, distinct mitochondrial DNA sequence (N...

Proper management of marine fisheries requires an understanding of the spatial and temporal dynamics of marine populations, which can be obtained from genetic data. While numerous fisheries species have been surveyed for spatial genetic patterns, temporally sampled genetic data is not available for many species. We present a phylogeographic survey...

Interspecies hybridisation in nature is a well-studied phenomenon, but has not been detected in the class Chondrichthyes (sharks, rays and chimeras). Two black-tip whaler shark species (Australian, Carcharhinus tilstoni; Common, C. limbatus) have overlapping distributions in Australia, distinct mitochondrial DNA sequence (ND4, COI, control region)...

This study used mtDNA sequence and microsatellite markers to elucidate the population structure of Scomberomorus semifasciatus collected from 12 widespread sampling locations in Australia. Samples (n = 544) were genotyped with nine microsatellite loci, and 353 were sequenced for the control (384 bp) and ATPase (800 bp) mtDNA gene regions. Combined...

Biodiversity of sharks in the tropical Indo-Pacific is high, but species-specific information to assist sustainable resource exploitation is scarce. The null hypothesis of population genetic homogeneity was tested for scalloped hammerhead shark (Sphyrna lewini, n=237) and the milk shark (Rhizoprionodon acutus, n=207) from northern and eastern Austr...

The diversity of geographic scales at which marine organisms display genetic variation mirrors the biophysical and ecological complexity of dispersal by pelagic larvae. Yet little is known about the effect of larval ecology on genetic population patterns, partly because detailed data of larval ecology do not yet exist for most taxa. One species for...

Tropical Australian shark fisheries target two morphologically indistinguishable blacktip sharks, the Australian blacktip (Carcharhinus tilstoni) and the common blacktip (C. limbatus). Their relative contributions to northern and eastern Australian coastal fisheries are unclear because of species identification difficulties. The two species differ...

The parasite fauna of the blue threadfin Eleutheronema tetradactylum, collected from 14 sites across northern Australia, was examined to evaluate the degree of movement and subsequent stock structure of the fish. Univariate and multivariate analysis of nine 'permanent' parasite species [the nematodes Anisakis (type I) and Terranova (type II), the c...

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...

Small-scale and artisanal fisheries for sharks exist in most inshore, tropical regions of the world. Although often important in terms of food security, their low value and inherent complexity provides an imposing hurdle to sustainable management. An observer survey of a small-scale commercial gill-net fishery operating within the Great Barrier Ree...

Understanding spatial patterns in demographic parameters of exploited fish species is of critical importance to effective fisheries management. In the present study, patterns in demography of a large, protandrous, estuarine teleost, king threadfin, Polydactylus macrochir, were compared among three estuaries on the eastern coast of Queensland, Austr...

Fish growth is commonly estimated from length-at-age data obtained from otoliths. There are several techniques for estimating length-at-age from otoliths including 1) direct observed counts of annual increments; 2) age adjustment based on a categorization of otolith margins; 3) age adjustment based on known periods of spawning and annuli formation;...

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...

Biased estimates of population parameters for harvested stocks can have severe implications for fishery management strategy choices. Hook-and-line fishing gear is size-selective and therefore collects biased samples from wild populations. Such biases may also vary in space and time. To assess this assertion, we compared line-and spear-caught sample...

The stable isotopes of δ18O and δ13C in sagittal otolith carbonates were used to determine the stock structure of Grey Mackerel, Scomberomorus semifasciatus. Otoliths were collected from Grey Mackerel at ten locations representing much of their distributional and fisheries range across northern Australia from 2005 to 2007. Across this broad range (...

Demographic parameters from seven exploited coral reef lutjanid species were compared as a case study of the implications of intrafamily variation in life histories for multispecies harvest management. Modal lengths varied by 4 cm among four species (Lutjanus fulviflamma, L. vitta, L. carponotatus, L. adetii), which were at least 6 cm smaller than...

Promotion of better procedures for releasing undersize fish, advocacy of catch-and-release angling, and changing minimum legal sizes are increasingly being used as tools for sustainable management of fish stocks. However without knowing the proportion of released fish that survive, the conservation value of any of these measures is uncertain. We de...

Abstract  Common coral trout, Plectropomus leopardus Lacepède, crimson snapper, Lutjanus erythropterus Bloch, saddletail snapper, Lutjanus malabaricus (Bloch & Schneider), red emperor, Lutjanus sebae (Cuvier), redthroat emperor, Lethrinus miniatus (Schneider) and grass emperor, Lethrinus laticaudis Alleyne & Macleay, were tagged to determine the ef...

The scombrid Scomberomorus semifasciatus is an important component of inshore fisheries in tropical Australia. Data on the parasite fauna of 593 fish from areas off northern and eastern Australia were examined for evidence of discrete fish populations. The parasites used were juveniles of Pterobothrium pearsoni, Callitetrarhynchus gracilis, Anisaki...

Marine capture fisheries are an important source of protein globally, with coastal and oceanic fish providing a rich source of essential fatty acids, vitamins, and minerals. Fisheries also support economies and important social structures in many nations, particularly developing nations (Allison et al., 2009). Marine fisheries are under increasing...

Species in the coral trout complex Plectropomus spp. are some of the most desired and exploited in the Indo-Pacific, although data are limited for most species. Demographic parameters of blue-spot coral trout, Plectropomus laevis, were estimated on the basis of specimens collected from five regions of the Great Barrier Reef and Torres Strait, Austr...

The humpback grouper Cromileptes altivelis is listed as Vulnerable on the IUCN Red List because of concerns about unsustainable levels of harvest. Quantitative estimates of life history parameters are scarce, limiting formal assessment of long-term harvest rates and conservation risk and the design of robust management measures. We provide the firs...

Blue threadfin Eleutheronema tetradactylum (Polynemidae) were examined from four areas (Princess Charlotte Bay, Trinity Inlet, Halifax Bay and Upstart Bay) in eastern Queensland covering a distance of c. 950 km of coastline. Parasites were used as biological markers to infer stock structure of E. tetradactylum. Parasites designated as 'temporary' b...

Three data sets were examined to define the level of interaction of reef associated sharks with the commercial Coral Reef Fin Fish Fishery within the Great Barrier Reef (GBR). Data were examined from fishery logbooks, an observer program within the fishery and a fishery-independent survey conducted as part of the Effects of Line Fishing (ELF) Exper...

This report provides preliminary results on 678 reef sharks counted by freedivers participating in The Great Australian Shark Count (GASC) in the Coral Sea and Great Barrier Reef waters between October and December 2007. Data reported here were collected using two different methodologies: Dedicated counts and Opportunistic counts. The most common s...

The Queensland Great Barrier Reef line fishery in Australia is regulated via a range of input and output controls including minimum size limits, daily catch limits and commercial catch quotas. As a result of these measures a substantial proportion of the catch is released or discarded. The fate of these released fish is uncertain, but hook-related...

Discarding in commercially exploited fisheries has received considerable attention in the last decade, though only more recently in Australia. The Reef Line fishery (RLF) of the Great Barrier Reef (GBR) in Australia is a large-scale multi-sector, multi-species, highly regulated hook and line fishery with the potential for high levels of discarding....

Commercially fished holothurians have important functions in nutrient recycling, which increases the benthic productivity of coral reef ecosystems. Thus, removal of these animals through fishing may reduce the overall productivity of affected coral reefs. To investigate the potential for recovery of overfished holothurian ( Holothuria nobilis) stoc...

The narrow-barred Spanish mackerel, Scomberomorus commerson, is an important target species of both commercial and recreational fishers across northern Australia. In Queensland distinct stocks have been identified from the Gulf of Carpentaria, Torres Strait, and the east coast. An assessment of the east coast stock is reported here. Commercial catc...