Scale- and Context-Dependent Selection of Recreational Harvest Estimation Methods: The Australasian Experience

Fisheries managers are becoming increasingly aware of the need to quantify all forms of harvest, including that by recreational fishers. This need has been driven by both a growing recognition of the potential impact that noncommercial fishers can have on exploited resources and the requirement to allocate catch limits between different sectors of the wider fishing community in many jurisdictions. Marine recreational fishers are rarely required to report any of their activity, and some form of survey technique is usually required to estimate levels of recreational catch and effort. In this review, we describe and discuss studies that have attempted to estimate the nature and extent of recreational harvests of marine fishes in New Zealand and Australia over the past 20 years. We compare studies by method to show how circumstances dictate their application and to highlight recent developments that other researchers may find of use. Although there has been some convergence of approach, we suggest that context is an important consideration, and many of the techniques discussed here have been adapted to suit local conditions and to address recognized sources of bias. Much of this experience, along with novel improvements to existing approaches, have been reported only in "gray" literature because of an emphasis on providing estimates for immediate management purposes. This paper brings much of that work together for the first time, and we discuss how others might benefit from our experience.

The complete validated mitochondrial genome of the silver gemfish Rexea solandri (Cuvier, 1832) (Perciformes, Gempylidae)

The silver gemfish Rexea solandri is an important economic resource but vulnerable to overfishing in Australian waters. The complete mitochondrial genome sequence is described from 1.6 million reads obtained via next generation sequencing. The total length of the mitogenome is 16,350 bp comprising 2 rRNA, 13 protein-coding genes, 22 tRNA and 2 non-coding regions. The mitogenome sequence was validated against sequences of PCR fragments and BLAST queries of Genbank. Gene order was equivalent to that found in marine fishes.

Developments in controlled green-water larval culture technologies for estuarine fishes in Queensland, Australia and elsewhere

Since 1989, researchers with the Department of Primary Industries and Fisheries (DPI&F) in Queensland, Australia, have successfully used controlled low-water exchange green-water cultures to rear the larvae of estuarine fishes and crustaceans through to metamorphosis. High survivals and excellent fry condition have been achieved for several commercially important endemic species produced for various projects. They include barramundi or sea bass, Lates calcarifer, Australian bass, Macquaria novemaculeata, dusky flathead, Platycephalus fuscus, sand whiting, Sillago ciliata, red sea bream or snapper, Pagrus auratus, banana prawn, Fenneropenaeus merguiensis, and others. The consistent success of our standardised and relatively simple approach at different localities has led to it being incorporated into general fingerling production practices at several establishments in Australia. Although post-metamorphosis rearing methods have differed for each species investigated, due to various biological and behavioural traits and project requirements, these larval rearing methods have been successful with few species-specific modifications. Initially modelled on the Taiwanese approach to rearing Penaeids in aerated low-water exchange cultures, the approach similarly appears to rely on a beneficial assemblage of micro-organisms. Conceptually, these micro-organisms may include a mixture of the air-borne primary invaders of pure phytoplankton cultures when exposed to outdoor conditions. Whilst this would vary with different sites, our experiences with these methods have consistently been favourable. Mass microalgal cultures with eco-physiological youth are used to regularly augment larval fish cultures so that rearing conditions simulate an exponential growth-phase microalgal bloom. Moderate to heavy aeration prevents settlement of particulate matter and encourages aerobic bacterial decomposition of wastes. The green-water larval rearing approach described herein has demonstrated high practical utility in research and commercial applications, and has greatly simplified marine finfish hatchery operations whilst generally lifting production capacities for metamorphosed fry in Australia. Its potential uses in areas of aquaculture other than larviculture are also discussed.

A comparison of the electrosensory morphology of a euryhaline and a marine stingray

The electrosensory system is found in all chondrichthyan fishes and is used for several biological functions, most notably prey detection. Variation in the physical parameters of a habitat type, i.e. water conductivity, may influence the morphology of the electrosensory system. Thus, the electrosensory systems of freshwater rays are considerably different from those of fully marine species; however, little research has so far examined the morphology and distribution of these systems in euryhaline elasmobranchs. The present study investigates and compares the morphology and distribution of electrosensory organs in two sympatric stingray species: the (euryhaline) estuary stingray, Dasyatis fluviorum, and the (marine) blue-spotted maskray, Neotrygon kuhlii. Both species possess a significantly higher number of ventral electrosensory pores than previously assessed elasmobranchs. This correlates with a diet consisting of benthic infaunal and epifaunal prey, where the electrosensory pore distribution patterns are likely to be a function of both ecology and phylogeny. The gross morphology of the electrosensory system in D. fluviorum is more similar to that of other marine elasmobranch species, rather than that of freshwater species. Both D. fluviorum and N. kuhlii possess 'macro-ampullae' with branching canals leading to several alveoli. The size of the pores and the length of the canals in D. fluviorum are smaller than in N. kuhlii, which is likely to be an adaptation to habitats with lower conductivity. This study indicates that the morphology of the electrosensmy system in.a euryhaline elasmobranch species seems very similar to that of their fully marine counterparts. However, some morphological differences are present between these two sympatric species, which are thought to be linked to their habitat type. (C) 2013 Elsevier GmbH. All rights reserved.

Reproductive biology of the red throat emperor Lethrinus miniatus (Pisces : Lethrinidae) from the southern Great Barrier Reef, Australia

The reproductive biology of the red throat emperor, Lethrinus miniatus (Schneider, 1801) was examined in the southern Great Barrier Reef (GBR), Australia. The species was found to display the characteristics of an incomplete metagynous hermaphrodite based on histological evidence and size frequency information. Over 95% of functional males possessed a remnant lumen, but there was no evidence of oocytes in the testes of males. A single transitional fish was sampled which had both ovarian and testicular tissue present in its gonad. Size frequency data showed that females dominated the smaller size classes with the majority of fish < 40 cm being females. Lethrinus miniatus had an extended spawning season from July-November, although spawning was more pronounced during the spring. Spawning was initiated earlier at lower latitudes. There was no particular size or age when sex change occurred since females older than 20 and males as young as 2-yrs old were sampled.

The Biosynthesis of Sesquiterpene Isocyanides and Isothiocyanates in the Marine Sponge Acanthella cavernosa (Dendy); Evidence for Dietary Transfer to the Dorid Nudibranch Phyllidiella pustulosa

The tropical marine sponge Acanthella cavernosa (Dendy) converts potassium [14C] cyanide to axisonitrile-3 (1); this precursor is also used for the synthesis of axisothiocyanate-3 (2) suggesting that isocyanides are precursors to isothiocyanates in A. cavernosa. Likewise, potassium [14C] thiocyanate is used for the synthesis of axisothiocyanate-3; unexpectedly this precursor also labelled axisonitrile-3. These results demonstrate either an interconversion between cyanide and thiocyanate prior to secondary metabolite formation or that the secondary metabolites can themselves be interconverted. Specimens of the dorid nudibranch Phyllidiellu pustulosa, preadapted to a diet of A. cavernosa, fed on 14C-labelled sponges and were subsequently found to contain the radioactive terpenes (1) and (2). Specimens of P. pustulosa, which had not expressed a dietary preference for A. cavernosa in the field, did not generally feed in aquarium tests with 14C-labelled sponges and, therefore, provided non-radioactive extracts. Since control experiments demonstrated the inability of P. pustulosa to synthesise the metabolites de novo, we therefore conclude that P. pustulosa acquires secondary metabolites by dietary transfer from A. cavernosa.

Quantitative assessment of total and Gram-positive aerobic bacteria in fresh and ambient-temperature-stored sub-tropical marine fish

The current study was undertaken to enumerate Gram-positive bacteria in fresh sub-tropical marine fish and determine the effect of ambient storage (25°C) on the Gram-positive bacterial count. Total and Gram-positive bacteria were enumerated in the muscles, gills and gut of fresh and stored Pseudocaranx dentex, Pagrus auratus and Mugil cephalus on tryptone soya agar (TSA) and TSA with 0.25% phenylethyl alcohol (PEA), respectively. Initial studies indicated that PEA significantly reduced total aerobic bacterial count (TABC) whereas control Gram-positive bacteria were not affected by 0.25% PEA. TABC significantly increased in all fish body parts, whereas Gram-positive aerobic bacterial count (GABC) significantly increased only in the muscles and gills during ambient storage for 15 h. The TABC of the fish species increased from 4.00, 6.13 and 4.58 log cfu g-1, respectively in the muscles, gills, and gut to 6.31, 7.31 and 7.23 log cfu g-1 by the end of storage. GABC increased from 2.00, 3.52 and 2.20 log cfu g-1 to 4.70, 5.85 and 3.36 log cfu g-1. Within each species, TABC were significantly higher in the gills compared to that of muscles and gut; however, no significant differences were found in GABC between muscles and gills. This study demonstrated the potential importance of Gram-positive bacteria in sub-tropical marine fish and their spoilage.

Production of microalgal concentrates by flocculation and their assessment as aquaculture feeds

A novel technique was developed for the flocculation of marine microalgae commonly used in aquaculture. The process entailed an adjustment of pH of culture to between 10 and 10.6 using NaOH, followed by addition of a non-ionic polymer Magnafloc LT-25 to a final concentration of 0.5 mg L-1. The ensuing flocculate was harvested, and neutralised giving a final concentration factor of between 200- and 800-fold. This process was successfully applied to harvest cells of Chaetoceros calcitrans, C. muelleri, Thalassiosira pseudonana, Attheya septentrionalis, Nitzschia closterium, Skeletonema sp., Tetraselmis suecica and Rhodomonas salina, with efficiencies >=80%. The process was rapid, simple and inexpensive, and relatively cost neutral with increasing volume (cf. concentration by centrifugation). Harvested material was readily disaggregated to single cell suspensions by dilution in seawater and mild agitation. Microscopic examination of the cells showed them to be indistinguishable from corresponding non-flocculated cells. Chlorophyll analysis of concentrates prepared from cultures of Concentrates of T. pseudonana prepared using pH-induced flocculation gave better growth of juvenile Pacific oysters (Crassostrea gigas) than concentrates prepared by ferric flocculation, or centrifuged concentrates using a cream separator or laboratory centrifuge. In follow up experiments, concentrates prepared from 1000 L Chaetoceros muelleri cultures were effective as supplementary diets to improve the growth of juvenile C. gigas and the scallop Pecten fumatus reared under commercial conditions, though not as effective as the corresponding live algae. The experiments demonstrated a proof-of-concept for a commercial application of concentrates prepared by flocculation, especially for use at a remote nursery without on-site mass-algal culture facilities.

Spatio-temporal patterns in maturation of the chokka squid (Loligo vulgaris reynaudii) off the coast of South Africa

Knowledge of the temporal and spatial characteristics of chokka squid (Loligo vulgaris reynaudii) biology in South African waters is limited, so the possibility of there being a geographically fragmented stock was examined by investigating the distribution of maturity patterns for the species, covering all known spawning areas and using both historical and recent data. Gonadosomatic indices (GSI) varied between year-round consistency and apparent seasonal peaks in both summer and winter; there was no clear spatial pattern. Monthly percentage maturity provided further evidence for two peak reproductive periods each year, although mature squid were present throughout. Sex ratios demonstrated great variability between different areas and life history stages. Male-biased sex ratios were only apparent on the inshore spawning grounds and ranged between 1.118:1 and 4.267:1. Size at sexual maturity was also seasonal, squid maturing smaller in winter/spring than in summer/autumn. Also, squid in the east matured smaller than squid in the west. Although the results from the present study do not provide conclusive evidence of distinct geographic populations, squid likely spawn over a significantly larger area of the Agulhas Bank than previously estimated, and squid on the west coast of South Africa may return to spawn on the western portion of the Agulhas Bank. It remains likely, however, that the east and west coast populations are a single stock and that migration of juveniles to the west coast and their subsequent return as sub-adults is an integral but non-essential and variable part of the life history.

Incorporating dugong habitats into the marine protected area design for the Great Barrier Reef Marine Park, Queensland, Australia.

Dugong habitats were considered in the design for the new zoning network for the Great Barrier Reef Marine Park as part of the Representative Areas Program. One of the specific design guidelines developed as part of the biophysical operational principles recommended that 50% of all high priority dugong habitats should be incorporated in the network of no-take areas. The high priority dugong habitat incorporated in no-take protection increased from 1396 to 3476 km2 (or 16.9-42.0% of all identified sites). Although this increase in protection fell short of the recommended 50%, overall the level of protection afforded by the Great Barrier Reef Marine Park Zoning Plan 2003 increased for all the locations identified.

Reproductive biology of mangrove jack (Lutjanus argentimaculatus) in northeastern Queensland, Australia

Lutjanus argentimaculatus is an Indo-Pacific species that inhabits riverine, coastal and offshore reef habitats. An investigation of the reproductive biology of Lutjanus argentimaculatus in northeastern Queensland waters (Australia) was undertaken between 1999 and 2002. Individuals in inshore estuarine and freshwater riverine habitats were mostly immature whereas those captured in offshore reef waters were predominantly mature. Males matured at a smaller size than females, with the length-at-50%-maturity (Lm50) for males estimated to be 470.7 mm fork length (FL) and 531.4 mm FL for females. The spawning season in northeastern Queensland was mostly during the austral spring-summer and peaked in December. The presence of ripe female fish and occurrence of postovulatory follicles in histological sections provided evidence that spawning activity was more pronounced during the full and third quarter moon phases. Lutjanus argentimaculatus were highly fecund with estimates of up to 4 x 106 ova per spawning event. Immature fish concentrated in inshore areas where they were targeted by recreational fishers whereas, in offshore areas, commercial fishers caught predominantly larger, mature fish.

A spatial assessment of the risk to a mobile marine mammal from bycatch

Several species of marine mammals are at risk of extinction from being captured as bycatch in commercial fisheries. Various approaches have been developed and implemented to address this bycatch problem, including devices and gear changes, time and area closures and fisheries moratoria. Most of these solutions are difficult to implement effectively, especially for artisanal fisheries in developing countries and remote regions. Re-zoning of the Great Barrier Reef World Heritage Area (GBRWHA) in 2004 closed 33% of the region to extractive activities, including commercial fishing. However, the impact of re-zoning and the associated industry restructuring on a threatened marine mammal, the dugong (Dugong dugon), is difficult to quantify. Accurate information on dugong bycatch in commercial nets is unavailable because of the large geographic extent of the GBRWHA, the remoteness of the region adjacent to the Cape York Peninsula where most dugongs occur and the artisanal nature of the fishery. In the face of this uncertainty, a spatial risk-assessment approach was used to evaluate the re-zoning and associated industry restructuring for their ability to reduce the risk of dugong bycatch from commercial fisheries netting. The new zoning arrangements appreciably reduced the risk of dugong bycatch by reducing the total area where commercial netting is permitted. Netting is currently not permitted in 67% of dugong habitats of high conservation value, a 56% improvement over the former arrangements. Re-zoning and industry restructuring also contributed to a 22% decline in the spatial extent of conducted netting. Spatial risk assessment approaches that evaluate the risk of mobile marine mammals from bycatch are applicable to other situations where there is limited information on the location and intensity of bycatch, including remote regions and developing countries where resources are limited.

Seagrass-Watch: Engaging Torres Strait Islanders in marine habitat monitoring

Involvement in scientifically structured habitat monitoring is a relatively new concept to the peoples of Torres Strait. The approach we used was to focus on awareness, and to build the capacity of groups to participate using Seagrass-Watch as the vehicle to provide education and training in monitoring marine ecosystems. The project successfully delivered quality scientifically rigorous baseline information on the seasonality of seagrasses in the Torres Strait-a first for this region. Eight seagrass species were identified across the monitoring sites. Seagrass cover varied within and between years. Preliminary evidence indicated that drivers for seagrass variability were climate related. Generally, seagrass abundance increased during the north-west monsoon (Kuki), possibly a consequence of elevated nutrients, lower tidal exposure times, less wind, and higher air temperatures. Low seagrass abundance coincided with the presence of greater winds and longer periods of exposure at low tides during the south-east trade wind season (Sager). No seasonal patterns were apparent when frequency of disturbance from high sedimentation and human impacts was high. Seagrass-Watch has been incorporated in to the Thursday Island High School's Marine Studies Unit ensuring continuity of monitoring. The students, teachers, and other interested individuals involved in Seagrass-Watch have mastered the necessary scientific procedures to monitor seagrass meadows, and developed skills in coordinating a monitoring program and skills in mentoring younger students. This has increased the participants' self-esteem and confidence, and given them an insight into how they may participate in the future management of their sea country.

Marine resources, biophysical processes, and environmental management of a tropical shelf seaway: Torres Strait, Australia-Introduction to the special issue

This special issue of Continental Shelf Research contains 20 papers giving research results produced as part of Australia's Torres Strait Co-operative Research Centre (CRC) Program, which was funded over a three-year period during 2003-2006. Marine biophysical, fisheries, socioeconomic-cultural and extension research in the Torres Strait region of northeastern Australia was carried out to meet three aims: 1) support the sustainable development of marine resources and minimize impacts of resource use in Torres Strait; 2) enhance the conservation of the marine environment and the social, cultural and economic well being of all stakeholders, particularly the Torres Strait peoples; and 3) contribute to effective policy formulation and management decision making. Subjects covered, including commercial and traditional fisheries management, impacts of anthropogenic sediment inputs on seagrass meadows and communication of science results to local communities, have broad applications to other similar environments.

Mapping and characterisation of the inter-reefal benthic assemblages of the Torres Strait

A comprehensive survey of the benthic assemblages of the Torres Strait was conducted in order to provide critical baseline information for regional marine planning, assessing the environmental sustainability of fisheries and understanding the ecosystems of the region. Over 150 sites throughout the region were sampled with a modified prawn trawl, towed underwater video, pipe dredge and epibenthic sled. This manuscript provides a broad overview of the activities undertaken and data collected. Two thousand three hundred and seventy-two different nominal species were sampled by the trawl and sled, only 728 by both gears. The towed video was not able to provide the same level of taxonomic resolution of epibenthic taxa, but was particularly useful in areas where the seabed was too rough to be sampled. Data from the trawl, sled and video were combined to characterise the epibenthic assemblages of the region. Data from the towed video was also used to provide a characterisation of the inter-reefal benthic habitats, which was then analysed in combination with physical covariate data to examine relationships between the two. Levels of mud and gravel in the sediments, trawling effort and seabed current stress were the covariates most significantly correlated with the nature of the seabed habitats.