Key Target Species Research Articles

Bacterial structures and their associated ARGs in Shanghai subway air, China

The air in the metro or subway system, which is a major form of public transportation in many metropolises, contributes to the transmission of pathogenic microorganisms. In this study, 18 aerosol samples were collected from two typical Shanghai subway stations (A and B) in the summer, transition, and winter seasons. Bacterial communities and their associated antibiotic resistance genes (ARGs) were analyzed using shotgun metagenomic sequencing. Metagenomic analysis approaches and random forest classification were used to compare and screen the distribution of key target species and ARGs. Bacteria were the predominant microbial kingdom with a relative abundance of 88.28%. In total, 5303 bacterial species were identified in subway stations A and B. The top three abundant bacterial species were unclassified_Pseudomonas, Ewingella_americana, and Halalkalicoccus_subterraneus. Microbial diversity analysis revealed that the microbial communities significantly varied between the three seasons (P < 0.05). Additionally, factors, such as temperature, relative humidity, and fine particulate matter (PM2.5) significantly influenced bacterial community structure (P < 0.05). The random forest algorithm was used to screen indicators in bacterial communities. Some of these bacterial communities, which were primarily derived from environmental sources, may pose health risks. In total, 312 ARGs subtypes related to 20 ARGs classes were identified in subway stations A and B. Random forest classification results revealed 20 indicative types of ARGs, including those involved in metabolizing aminoglycoside, beta-lactam, multidrug, and rifamycin-type antibiotics. This study provides novel insights into microbial communities and ARGs in typical subway micro-environments and their dissemination in subway environments.

DNA analyses of large pangolin scale seizures: Species identification validation and case studies

Pangolins are the most trafficked mammal in the world, and all eight species are listed under CITES Appendix I. DNA-based wildlife forensic techniques are recognized as an important component of investigating a pangolin seizure. In particular, determining the species of pangolin in a seizure will 1) confirm the presence of pangolin to establish the legality of any trade, and 2) ensure appropriate laws are applied to their fullest extent in a prosecution. Furthermore, valuable intelligence data, such as determining the geographic provenance of samples, can be produced through analysis of pangolin seizures. Despite the immense scale of the pangolin trade, standardized wildlife forensic techniques for testing pangolin seizures are in their infancy. To address this, here, we present a standardized genetic marker suitable for species identification of all eight pangolin species, and outline practical strategies for sampling large-volume pangolin scale seizures. We assessed the repeatability, reproducibility, robustness, sensitivity and phylogenetic resolution of this species identification test. Critically, the assay was tested in four wildlife forensic laboratories involved in testing pangolins. Additionally, we demonstrated the test’s utility to conduct geographic provenance analysis of Phataginus tricuspis samples. We analysed five large-volume pangolin scale seizures in Malaysia, which elucidated key target species, poaching hotspots, and trafficking routes. Phataginus tricuspis was the most commonly identified species (88.8%) from the seizure samples, and 84.3% of these P. tricuspis individuals were likely sourced from western central Africa. We expect the implementation of the techniques presented in this paper will improve enforcement of pangolin trafficking crimes.

Supporting Spatial Management of Data-Poor, Small-Scale Fisheries With a Bayesian Approach

Marine conservation areas are an important tool for the sustainable management of multispecies, small-scale fisheries. Effective spatial management requires a proper understanding of the spatial distribution of target species and the identification of its environmental drivers. Small-scale fisheries, however, often face scarcity and low-quality of data. In these situations, approaches for the prioritization of conservation areas need to deal with scattered, biased, and short-term information and ideally should quantify data- and model-specific uncertainties for a better understanding of the risks related to management interventions. We used a Bayesian hierarchical species distribution modeling approach on annual landing data of the heavily exploited, small-scale, and data-poor fishery of Chwaka Bay (Zanzibar) in the Western Indian Ocean to understand the distribution of the key target species and identify potential areas for conservation. Few commonalities were found in the set of important habitat and environmental drivers among species, but temperature, depth, and seagrass cover affected the spatial distribution of three of the six analyzed species. A comparison of our results with information from ecological studies suggests that our approach predicts the distribution of the analyzed species reasonably well. Furthermore, the two main common areas of high relative abundance identified in our study have been previously suggested by the local fisher as important areas for spatial conservation. By using short-term, catch per unit of effort data in a Bayesian hierarchical framework, we quantify the associated uncertainties while accounting for spatial dependencies. More importantly, the use of accessible and interpretable tools, such as the here created spatial maps, can frame a better understanding of spatio-temporal management for local fishers. Our approach, thus, supports the operability of spatial management in small-scale fisheries suffering from a general lack of long-term fisheries information and fisheries independent data.

Partially protected areas as a management tool on inshore reefs

Partially Protected Areas (PPAs) are a widely-used management tool, yet comparatively little is known about their effectiveness compared to more commonly studied No-Take Marine Reserves (NTMRs). Here, we examine the efficacy of two kinds of PPAs (with and without spearfishing) within the Great Barrier Reef Marine Park (GBRMP) that are subject to a range of fishing limitations, and assess their utility as a marine park zoning and fisheries management tool. Fish abundance, size, and habitat composition were compared inside PPAs and NTMRs on inshore reefs of the central GBR. Fish abundances were lower inside PPAs relative to adjacent NTMRs for primary fishing targets, with no detectable effects for secondary targets and non-targets, or for species richness. Fish assemblages differed amongst zones, but these variations were minor compared to regional variations in species composition. Partially Protected Areas supported 46%–69% of the relative abundance of total primary targets compared to adjacent NTMRs, with no evident increase in abundance in zones where spearfishing was prohibited. There were no reductions in the size of two key target species: coral trout (Plectropomus spp.) and stripey snapper (Lutjanus carponotatus) inside PPAs, and only stripey snapper had significant reductions in abundance inside PPAs compared to NTMRS. Habitat and biophysical characteristics (especially topographic complexity) were strong drivers of fish abundance, but the relative influence of zone was greater for target species compared to non-targets. This study provides novel data on PPAs and highlights their utility as a spatial management tool in contributing to conservation and fisheries management goals.

Red Sea fish market assessments indicate high species diversity and potential overexploitation

In many parts of the world, particularly remote and underdeveloped regions, reports of fisheries catch, effort, and landing data are limited. In order to implement effective fishing regulations to protect natural stocks, understanding fishing pressure, key target species, catch composition, and value of each species is vital. In regions where published data is limited, and the sampling of numerous small boats and landing sites is not feasible, fish market surveys represent an opportunity to obtain key fisheries data. This study therefore aims to obtain species-specific prices and market composition for fish landed in the central Red Sea by surveying local fish markets. We conducted 11 surveys at two major Red Sea fish markets to ascertain key fisheries metrics using market data as a proxy for catch data. Results indicate that a high proportion of the market composition is generated by 46 species from six family-level groups, Serranidae, Labridae, scarine labrids, Carangidae, Lethrinidae, and Lutjanidae, contributing to 87 % of the total market biomass. Species-specific values ranged from 4.50 USD/kg to 26.44 USD/kg, with market surveys highlighting the economic value of three local serranid species: Plectropomus pessuliferus marisrubri, Plectropomus areolatus and Variola louti, all valued at more than 25 USD/kg, and a labrid: Cheilinus undulatus, valued at 26.44 USD/kg. The Serranidae family represents 47 % of the total biomass and 55 % of the potential revenue in the market, while also indicating potentially overfished reefs due to the high occurrence of smaller species and undersized individuals of higher priced serranid species. Many of the high-valued serranids were below the size at sexual maturity. Target species exhibited small body size and decreasing abundance, potentially indicating a “shrinking baseline” scenario occurring in the Saudi Arabian artisanal coral reef fishery. These results indicate that introducing effective fisheries legislation and management is necessary for the longevity and sustainability of the reef-based fishery in the Saudi Arabian Red Sea. Implementing catch quotas, size limits, and seasonal restrictions are potential mechanisms that could be used to facilitate positive change within this vulnerable fishery.

Effects and effectiveness of lethal shark hazard management: The Shark Meshing (Bather Protection) Program, NSW, Australia

Abstract ‘Shark attack’ presents a considerable social‐environmental challenge. Each year a small number of people are injured or killed by shark bite. Concurrently, sharks and other marine life are subject to unprecedented anthropogenic pressures. Shark hazard management varies globally, but lethal strategies are common, with negative consequences for species and environments. Of particular concern are the effects for threatened species. Lethal strategies have recently come under criticism, based on the negative effects for marine life, effectiveness for human safety and inconsistency with contemporary values. Moves to improve both safety and conservation can be hindered by polarized debate. We present a case study of the world's longest‐running lethal shark hazard management program, the Shark Meshing (Bather Protection) Program, New South Wales, Australia. We take an interdisciplinary approach to bring into conversation factors that contribute to safety and conservation outcomes. To date, most research focuses on one or other of these areas. We seek to synthesize the factors that are not previously considered in relation to each other. Our aims were to: (a) identify and critique the diverse factors that determine the outcomes of the program; (b) assess the negative effects of the program for sharks and other marine life; and (c) assess the effectiveness of the program for reducing threat of shark interactions. We find that: (a) multiple social and environmental factors contribute to program outcomes; (b) total shark numbers and populations of key target species – white shark (Carcharodon carcharias), tiger shark (Galeocerdo cuvier) and bull shark (Carcharhinus leucas) – have declined over the program's 80 years, as have a number of non‐target species; (c) incidence of shark bite has declined since the program's introduction, but two external points warrant attention. First, key factors influencing the shark bite incidence are frequently overlooked, namely changing cultures of beach‐ and ocean‐use, advances in beach patrol, and emergency and medical response. Second, the proportion of bites leading to fatality has decreased significantly in recent decades. Beach patrol and emergency response contribute to human safety and well‐being without the negative consequences of lethal strategies. As such, they offer a focus for future shark hazard management and research. A free Plain Language Summary can be found within the Supporting Information of this article.

Development of HyBeacon® probes for the forensic detection of Panthera, rhinoceros, and pangolin species

The Illegal Wildlife Trade (IWT) represents a multi-billion dollar black-market industry whereby wild species are illegally taken from their natural environment and sold. A common question asked by wildlife forensic scientists pertains to species and/or genus identity, which currently requires multi-step processing. Our work details the development of three HyBeacon® probes, used for the presumptive detection of rhinoceros, pangolin and key target species in the Panthera genus. The approach can be performed in a single tube using melt curve analysis and provide rapid assessment of sample identity. Using synthetic DNA of representative species, early data suggest the approach is sensitive enough to achieve species identification with <10 cells. Future development and assay validation can allow the rapid screening of multiple seized items before confirmatory DNA sequencing.

Retrospective application of transposon-directed insertion-site sequencing to investigate niche-specific virulence of Salmonella Typhimurium in cattle

BackgroundSalmonella enterica subspecies enterica is an animal and zoonotic pathogen of global importance. Cattle are a significant reservoir of human non-typhoidal salmonellosis and can suffer enteric and systemic disease owing to the ability of Salmonella to survive within the bovine lymphatic system and intestines. Contamination of food can occur due to the incorporation of contaminated peripheral lymph nodes or by direct contamination of carcasses with gut contents. It is essential to understand the mechanisms used by Salmonella to enter and persist within the bovine lymphatic system and how they differ from those required for intestinal colonization to minimize zoonotic infections.ResultsTransposon-directed insertion site sequencing (TraDIS) was applied to pools of mutants recovered from mesenteric lymph nodes (MLNs) draining the distal ileum of calves after oral inoculation with a library of 8550 random S. Typhimurium mini-Tn5Km2 mutants in pools of 475 mutants per calf. A total of 8315 mutants representing 2852 different genes were detected in MLNs and their in vivo fitness was calculated. Using the same improved algorithm for analysis of transposon-flanking sequences, the identity and phenotype of mutants recovered from the distal ileal mucosa of the same calves was also defined, enabling comparison with previously published data and of mutant phenotypes across the tissues. Phenotypes observed for the majority of mutants were highly significantly correlated in the two tissues. However, 32 genes were identified in which transposon insertions consistently resulted in differential fitness in the ileal wall and MLNs, suggesting niche-specific roles for these genes in pathogenesis. Defined null mutations affecting ptsN and spvC were confirmed to result in tissue-specific phenotypes in calves, thus validating the TraDIS dataset.ConclusionsThis validation of the role of thousands of Salmonella genes and identification of genes with niche-specific roles in a key target species will inform the design of control strategies for bovine salmonellosis and zoonotic infections, for which efficacious and cross-protective vaccines are currently lacking.

Fisheries assessment of Chwaka Bay (Zanzibar) - following a holistic approach

This study investigates the typical East African multispecies fishery of Chwaka Bay (Zanzibar) by assessing growth, mortality, exploitation and stock size of six key target species of the fishery. Analyses are based on monthly length–frequency data collected from January to June and September to December in 2014 from the three main landing sites surrounding the bay. Estimated von Bertalanffy growth parameters using the ELEFAN I routine as implemented in FiSAT II varied among species from 27.6 to 64.4 cm (L∞) and 0.24 to 0.8 per year (K). Current exploitation rates compared to biological reference points calculated from yield-per-recruit analysis for five of the six key species indicate that Siganus sutor, Lethrinus borbonicus and Lethrinus lentjan are harvested beyond maximum sustainable levels (Emax). While juvenile retention rates of these three species are >80% and current Lc-values are lower than Lopt, fishing mortalities for Siganus sutor and Lethrinus borbonicus are highest for specimens above length at first maturity. Two management measures are discussed: (i) an increase in mesh size; and (ii) closure of the destructive dragnet fishery. The first option seems feasible only if the radius of the fishery were increased to capture larger specimens outside the shallow bay area. The second option would leave approximately 550 fishermen unemployed. Reallocating dragnet fishing effort to other gears would lead to a substantial increase in the number of boats, which might create use conflicts over the limited fishing area. The general status of the fishery in Chwaka Bay is considered as representing a ‘full exploitation to over-exploitation scenario’, with no scope for expansion.

Spawning biomass of jack mackerel (Trachurus declivis) off eastern Australia: Critical knowledge for managing a controversial fishery

Jack mackerel (Trachurus declivis) is a key target species of the Australian Small Pelagic Fishery. The fishery was subject to extensive public scrutiny following an attempt to introduce a large factory-trawler in 2012. One of the concerns raised related to the reliability and age of estimates of the spawning biomass of jack mackerel. This study reports on the first dedicated application of the Daily Egg Production Method (DEPM) to jack mackerel. Large numbers of samples of eggs and adults were collected concurrently from the key spawning area off eastern Australia during what has been previously identified as the main spawning period. This study established an effective adult sampling method and provides the first estimates for this species of adult reproductive parameters required for application of the DEPM. Estimates of all DEPM parameters, except batch fecundity, were based on relatively large sample sizes. The spawning biomass of jack mackerel off eastern Australia during January 2014 was estimated to be approximately 157,805 t (95% CI=59,570–358,731 t). Sensitivity analyses indicate this estimate is robust to likely uncertainty in estimates of key parameters. Future research should focus on elucidating the size-fecundity relationship and spatial, temporal and size-related variations in spawning fraction.

Catch, effort and fishing practices in a recreational gillnet fishery: Assessing the impacts and response to management change

Gillnets are typically considered to be a commercial fishing gear yet their use by recreational fishers is permitted in several developed countries, often with few if any restrictions on the total number of users. Despite this there have been very few attempts to assess the impacts of recreational gillnet fisheries both in terms of harvest and implications for bycatch. Recreational gillnetting has a long history in Tasmania, Australia, and over the past two decades the fishery has been the focus of a number of management measures to improve fishing practices. In this study, the fishing activity of recreational gillnet license-holders was monitored for 12-months using a telephone-diary based panel survey. Catch, effort and fishing practices were compared with previous recreational fishing surveys and the commercial fishery. During 2010 an estimated 6600 recreational license-holders used gillnets, accounting for 25,712 (95%CI 22,142–28,901) net-days of effort and a total catch of 173,922 (95%CI 147,165–202,950) marine organisms, 35.5% of which were discarded. The recreational fishery is comprised of two main sub-fisheries, a mixed reef-fish fishery and a fishery for marine farm escapees. Four species, three representing key target species and one primarily a bycatch species, accounted for just over half of the total gillnet catch by number. The harvested component of the recreational gillnet catch was comparable to or exceeded commercial landings for the key species, highlighting the importance of taking account of the recreational fishery in stock assessments and species management. Despite an increase in the number of gillnet license-holders, recreational gillnet effort in Tasmania has halved since the late 1990s. This decline in effort appears to be linked to the greater regulation of fishing practices as well as reduced availability of two key target species, one of which has been classified as over-fished. Although recreational fishing practices have improved, the impacts on target and non-target species, including the incidental capture of seabirds and survival of bycatch, remain issues for concern.

When ‘fishing down the food chain’ results in improved food security: Evidence from a small pelagic fishery in Solomon Islands

Solomon Islanders are highly dependent on their coastal resources for food and livelihoods. Parts of some islands are now quite densely populated and some groups are being forced to adapt to resource scarcities. One such adaptation is the relatively recent development of nocturnal fisheries for small coastal pelagic fish in Langalanga Lagoon, Malaita Province, in tandem with declining reef fish stocks. The technique involves using lights to attract fish to gill nets and strike-lines deployed from dugout canoes anchored in and around lagoon passages. In the first detailed study of a fishery based on this gear combination in the Pacific, we report a mean catch-per-unit-effort (CPUE) from over 190 light fishing trips of 3.41kg/h/person. This figure is two to five times higher than CPUE’s obtained for reef-associated fisheries in Solomon Islands, including sites with much lower population and market pressures. The main targets of the light fishery were clupeids, along with small carangids, small sphyraenids and small scombrids. Interviews with fishers revealed there were regular seasonal fluctuations in the abundance of the dominant species (Amblygaster sirm, the Spotted Sardinella) but no long-term (i.e. decadal) variation. Langalanga people now rely heavily on this high-yielding fishery for subsistence and cash, and some said they would need to relocate in search of alternate livelihoods if it did not exist. The high fecundity, rapid growth, early maturation and short life span of the key target species indicate that stocks are likely to be much more resilient than those of most reef-associated species. Many aspects of the behaviour and ecology of the key species remain poorly understood. However we argue that this study should encourage more scientists and fishery managers to think beyond reef-centric and larval connectivity-based models of tropical coastal fishery production and food security, and to pay much closer attention to biological oceanographic processes, including nutrient inputs, which fundamentally underpin the productivity of these increasingly important small pelagic fisheries.

Pyrolysis Characteristics and Char Reactivity of Oedogonium sp. and Loy Yang Coal

The proposition of combining the application of algae in wastewater treatment, CO2 fixation, and energy production maximizes the opportunity of algal bioremediation. In this paper, the freshwater macroalga Oedogonium, a key target species for the bioremediation of waste waters, was investigated for its utilization in energy production via gasification or co-gasification with coal. The pyrolysis characteristics of Oedogonium and the effects of pyrolysis conditions on char reactivity were investigated in this paper, and an Australian lignite was also studied for comparison purposes. The pyrolysis process of Oedogonium and coal can be divided into three stages: moisture evaporation, volatile release, and decomposition of the remaining carbonaceous compounds. However, the devolatilization of Loy Yang coal was slower and occurred over a wider temperature range compared to Oedogonium. As the heating rate increased, the pyrolysis curves for both Oedogonium and Loy Yang coal shifted to higher temperatures. To investigate the effects of pyrolysis conditions on char reactivity, a tube reactor was employed to generate char samples under a range of pyrolysis conditions. The produced char samples were characterized using a CHN analyzer and scanning electron microscopy technique. It was found that char samples almost maintain their original shape following pyrolysis at a low heating rate. However, evidence of char swelling was observed in the structure of chars prepared at a high heating rate. Pyrolysis conditions also had a significant influence on the reactivity of the derived chars. Char reactivity for both fuels was enhanced at a higher heating rate and lower pyrolysis temperature. Oedogonium char reactivity was around 2–5 times that of Loy Yang char prepared under the same pyrolysis conditions. However, the differences in reactivity became less significant as the pyrolysis temperature increased. Oedogonium has a higher devolatilization rate and higher char reactivity than Loy Yang lignite. It implies that it is easier to be gasified, and the co-gasification with lignite is advantageous.

Differential response of fish assemblages to coral reef-based seaweed farming.

As the global demand for seaweed-derived products drives the expansion of seaweed farming onto shallow coral ecosystems, the effects of farms on fish assemblages remain largely unexplored. Shallow coral reefs provide food and shelter for highly diverse fish assemblages but are increasingly modified by anthropogenic activities. We hypothesized that the introduction of seaweed farms into degraded shallow coral reefs had potential to generate ecological benefits for fish by adding structural complexity and a possible food source. We conducted 210 transects at 14 locations, with sampling stratified across seaweed farms and sites adjacent to and distant from farms. At a seascape scale, locations were classified by their level of exposure to human disturbance. We compared sites where (1) marine protected areas (MPAs) were established, (2) neither MPAs nor blast fishing was present (hence “unprotected”), and (3) blast fishing occurred. We observed 80,186 fish representing 148 species from 38 families. The negative effects of seaweed farms on fish assemblages appeared stronger in the absence of blast fishing and were strongest when MPAs were present, likely reflecting the positive influence of the MPAs on fish within them. Species differentiating fish assemblages with respect to seaweed farming and disturbance were typically small but also included two key target species. The propensity for seaweed farms to increase fish diversity, abundance, and biomass is limited and may reduce MPA benefits. We suggest that careful consideration be given to the placement of seaweed farms relative to MPAs.

Dynamic Conservation of Forest Genetic Resources in 33 European Countries

Dynamic conservation of forest genetic resources (FGR) means maintaining the genetic diversity of trees within an evolutionary process and allowing generation turnover in the forest. We assessed the network of forests areas managed for the dynamic conservation of FGR (conservation units) across Europe (33 countries). On the basis of information available in the European Information System on FGR (EUFGIS Portal), species distribution maps, and environmental stratification of the continent, we developed ecogeographic indicators, a marginality index, and demographic indicators to assess and monitor forest conservation efforts. The pan-European network has 1967 conservation units, 2737 populations of target trees, and 86 species of target trees. We detected a poor coincidence between FGR conservation and other biodiversity conservation objectives within this network. We identified 2 complementary strategies: a species-oriented strategy in which national conservation networks are specifically designed for key target species and a site-oriented strategy in which multiple-target units include so-called secondary species conserved within a few sites. The network is highly unbalanced in terms of species representation, and 7 key target species are conserved in 60% of the conservation units. We performed specific gap analyses for 11 tree species, including assessment of ecogeographic, demographic, and genetic criteria. For each species, we identified gaps, particularly in the marginal parts of their distribution range, and found multiple redundant conservation units in other areas. The Mediterranean forests and to a lesser extent the boreal forests are underrepresented. Monitoring the conservation efficiency of each unit remains challenging; however, <2% of the conserved populations seem to be at risk of extinction. On the basis of our results, we recommend combining species-oriented and site-oriented strategies.

Progress in the development of DNA vaccines against foot-and-mouth disease

DNA vaccines are, in principle, the simplest yet most versatile methods of inducing protective humoral and cellular immune responses. Research involving this type of vaccine against veterinary diseases began in the early 1990s and has since seen the evaluation of more than 30 important viral pathogens, including the economically important foot-and-mouth disease. With the demonstration that DNA vaccines protect against foot-and-mouth disease in sheep and pigs, and the advantages these DNA vaccines have over the conventional formulations, this approach may provide a better solution to the control of this disease. In this review, we provide a comprehensive overview of DNA vaccination strategies for foot-and-mouth disease reported in the literature, in which we highlight the studies that have reported protection in the key target species.

Exploring gillnet catch efficiency of sardines in the coastal waters of Sri Lanka by means of three statistical techniques: a comparison of linear and nonlinear modelling techniques

The present investigation was undertaken to study the gillnet catch efficiency of sardines in the coastal waters of Sri Lanka using commercial catch and effort data. Commercial catch and effort data of small mesh gillnet fishery were collected in five fisheries districts during the period May 1999–August 2002. Gillnet catch efficiency of sardines was investigated by developing catch rates predictive models using data on commercial fisheries and environmental variables. Three statistical techniques [multiple linear regression, generalized additive model and regression tree model (RTM)] were employed to predict the catch rates of trenched sardine Amblygaster sirm (key target species of small mesh gillnet fishery) and other sardines (Sardinella longiceps, S. gibbosa, S. albella and S. sindensis). The data collection programme was conducted for another six months and the models were tested on new data. RTMs were found to be the strongest in terms of reliability and accuracy of the predictions. The two operational characteristics used here for model formulation (i.e. depth of fishing and number of gillnet pieces used per fishing operation) were more useful as predictor variables than the environmental variables. The study revealed a rapid tendency of increasing the catch rates of A. sirm with increased sea depth up to around 32 m.

Managing environmental impacts of fishing: input controls versus outcome-oriented approaches

Fishery management has focused primarily on limiting the total catch of key target species to sustainable levels, but fishery managers and the public are becoming increasingly concerned with environmental impacts of fishing such as damage to habitat and bycatch of non-target species, particularly marine mammals and seabirds. There are two main approaches to managing environmental impacts of fishing. The first is to prohibit or prescribe use of particular fishing gears and methods in particular areas either year-round or at specific times. The primary alternative is an outcome-oriented approach under which the environmental impacts are regulated directly, either by setting and monitoring limits on impacts by individuals or groups or by taxing impacts. This paper explores the factors that determine relative effectiveness and efficiency of input versus outcome-oriented approaches to managing environmental impacts of fishing. This paper highlights the role of technology in determining the preferable regulatory methods.

Optimising codend configuration in a multispecies demersal trawl fishery

Abstract The relative efficiencies and selectivities of conventional and modified codends were examined in a demersal trawl fishery targeting several species, including eastern king prawns, Penaeus plebejus (Hess), whiting, Sillago spp. and cephalopods. The modifications to codends included: (i) reducing the circumference; (ii) increasing the mesh size in conventional diamond‐mesh designs; and (iii) orientating meshes on the bar so that they were square shaped. The codends were tested against a fine‐meshed control in paired comparisons onboard three commercial trawlers. The conventional codend comprised 41‐mm diamond‐shaped mesh attached to an anterior extension section at a ratio of 150 to 100 meshes and was demonstrated to be non‐selective for the targeted species. Reducing codend circumference to 100 meshes and increasing the size of mesh to 45 mm both improved selection for eastern king prawns, but the lateral mesh openings were estimated to be insufficient to allow juveniles of the other key species to escape. By contrast, codends made from 35‐ and 41‐mm mesh hung on the bar improved the size selection for eastern king prawns and selected stout whiting, Sillago robusta (Stead) (the smallest commercial‐sized fish) across narrow selection ranges and at 50% sizes of retention (L50s) that were closely correlated to the transverse morphology of fish and the maximum mesh opening. With the exception of a reduction in catches of octopus, Octopus spp., by the 41‐square codend, there were no other impacts on commercial catches by the square‐mesh designs. It was concluded that diamond‐mesh codends are inappropriate for use throughout this multispecies fishery and that a modified design comprising at least 35‐mm mesh hung on the bar is required to minimise the fishing mortality of unwanted sizes of the key target species. The results are discussed in terms of the utility of these types of modifications for closely regulating selection in penaeid‐shrimp trawls.