Excavating sponges that are destructive to farmed pearl oysters in Western and Northern Australia

Species of the family Clionaidae (Porifera: Demospongiae) that excavate shell of the silver‐lip pearl oyster, Pinctada maxima, in north Western and Northern Australia are described. Two species belong to the genus Cliona and one species to the closely related genus Pione. Cliona orientalis has only recently been reported from Australia in living and dead coral on the Great Barrier Reef, and this is the first report of this species from north Western and Northern Australia. Cliona dissimilis is reported from Australia for the first time. Pione velans was first described from Shark Bay, Western Australia and this study extends its distribution from Albany, south Western Australia to Port Bremer in the Northern Territory. The most common species found was C. dissimilis. Pione velans and C. orientalis were also present, although the latter species was rare. Cliona dissimilis and P. velans were found to be sexually reproductive in some shells with specimens of C. dissimilis with oocytes in May and P. velans in September 1999. Egg development was synchronous, indicating that the sponges were oviparous and would broadcast gametes in a spawning event.     

Experimental sponge fishery in Egypt during recovery from sponge disease

• 1. A survey was undertaken (1995) on the Mediterranean coast of Egypt that investigated four sponge fishing grounds. These fishing banks suffered from sponge disease between 1987 and 1990, causing a mass mortality of commercial sponges in the eastern and central Mediterranean.
• 2. Adult commercial sponges (length >10 cm) were harvested by divers in the infralittoral zone (depth range 17–36 m). The substratum at most of the sampling stations was hard, consisting mainly of plaques, rocks and heavy stones, sometimes covered by Posidonia oceanica.
• 3. Two commercial sponge species were detected, Hippospongia communis and Spongia cfr zimocca; the former was more prevalent and abundant. Light penetration in the area surveyed was high. The two commercial sponge species detected seemed to be well adapted to these conditions, as indicated by the colour of their external membranes, which were almost black due to enhanced pigment formation. The absence of Spongia officinalis, in the area surveyed may also be related to light penetration, since S. officinalis is a more sciaphilous species.
• 4. The shape of H. communis was almost spherical, and the average dimensions (length, width, height, circumference) increased with increasing depth of the fishing grounds. At shallower depths (<30 m), adult H. communis occurred in lower densities, whereas young commercial sponges were abundant. No signs of sponge disease were found.
• 5. It is concluded that the recovery of the four sponge fishing grounds was in progress, and that the repopulation of commercial sponges in the infralittoral zone showed a gradient from deeper to shallower waters. It is recommended to prohibit destructive fishing methods in the deeper waters in order to protect the population and its ability to regenerate.

Copyright © 2005 John Wiley & Sons, Ltd.     

Optimising harvest strategies in a multi‐species bivalve fishery

Abstract Optimising harvests from fishery resources requires appropriate data. In this study, fishery‐independent survey and size‐at‐first maturity (L₅₀) data were used to assess the suitability of current minimum legal sizes (MLS) and total allowable commercial catches (TACC) in the South Australian, mixed‐species, mud‐cockle (Katelysia spp.) fishery. Estimates of L₅₀ suggested the MLS was conservative in one fishing zone (Coffin Bay), but appropriate elsewhere. Harvestable‐biomass estimates (HB) demonstrated that TACCs were excessive in the Port River (41% of HB), suitable in Coffin Bay (10% of HB) and precautionary in the West Coast (1.5% of HB) fishing zones. Consequently, the MLS was decreased by 5 mm shell length in Coffin Bay and the TACCs for the Port River (reduced by 80%) and West Coast (increased by 40%) amended. This study demonstrated that harvest strategies in mixed‐species fisheries can be optimised by explicitly considering data on species composition, abundance and population biology.     

Drivers of density for the exploited giant clam Tridacna maxima: a meta‐analysis

Giant clam populations have been over‐exploited throughout their range over the past decades for their meat and shells. Tridacna maxima, commonly known as the ‘small giant clam’, has remained relatively untargeted by fishers in areas where larger species occur (e.g. Tridacna squamosa), and high densities of the species are still observed on some isolated and enclosed reefs of the Central Pacific. However, it is unclear whether reported discrepancies in densities worldwide reflect differences in fishing pressure only or a combination of differences in exploitation levels and environmental forcing. We reviewed T. maxima surveys throughout its range to (i) identify patterns of density at global scale, site scale (e.g. island) and intrasite scale; (ii) discuss the influence of sampling method on density estimates; and (iii) identify the primary drivers of giant clam density along gradients of human pressure and natural forcing. We found 59 studies that reported density estimates for 172 sites across 26 countries in the Indo‐Pacific and Red Sea. At intrasite scale, densities were strongly dependent on sampling protocols and surveyed habitats. At site scale, we found close links between T. maxima density and human population per reef area, suggesting that isolated reefs where exploitation only recently started may be more vulnerable to stock collapse in the future. Density patterns were also found to vary significantly depending on reef type (e.g. atoll, island, continental coastline). We discuss how natural processes and fishing pressure may control population dynamics and densities among sites, and make recommendations for future research.     

Extraction of Chitin from the Shell Wastes of Two Shrimp Species Fenneropenaeus semisulcatus and Fenneropenaeus indicus using Microorganisms

Traditionally, chitin is extracted from crustacean shells using chemical methods involving the use of strong acids and alkali. In this study, chitin was extracted from the shrimp shell waste using microbes isolated from the fermented milk and bread. The chitin yield from the shells of Fenneropenaeus semisulcatus was 14.054% and 16.062%, respectively, for shell:bacterial broth ratios of 1:15 and 1:25; whereas, the yield of chitin from the shells of Fenneropenaeus indicus was 14.93% and 13.871%, respectively, at 1:15 and 1:25 broth ratios. The Fourier transform infrared spectra obtained from the chitin samples showed characteristic chitin peaks in both shell to bacterial broth ratio. The X-ray diffraction analysis revealed peaks between 10–15 and 25–30 degrees in the chitin recovered from both species, though some variations between species were observed. In conclusion, results of the present study indicate that application of microorganisms for the extraction of chitin from the shrimp shell waste could be an alternative for the traditional chemical methods.     

Sponge‐fishing,disease and farming in the Mediterranean Sea

1. Some Mediterranean sponge species belonging to the genera Spongia and Hippospongia, have been harvested for commercial purposes since ancient times. Recently, a widespread epidemic has greatly reduced the density of sponge populations which has had serious repercussions in the commercial field. 2. The synergetic action of harvesting and disease has taken a number of populations to the brink of extinction. Sponge‐population densities are steadily decreasing and their recovery after the disease event is incomplete and has taken a long time. 3. There is a simple solution to the problem: sponge‐farming. Trials have been underway since the beginning of the century and recently, Cuba, the Philippines and Micronesia Islands have started commercial sponge‐farming. 4. Sponges are naturally able to remove dissolved organic matter, organic particles and bacteria from the water‐column and this ability could be exploited in an integrated mariculture system. Floating cages for fish production result in the release of a lot of organic wastes that can be used as a source of food for surrounding intensive commercial sponge communities. Such an integrated system could result in effective eutrophication control, commercial sponge production and a consequent reduction of fishing effort on already heavily‐stressed natural sponge populations. Copyright © 1999 John Wiley & Sons, Ltd.     

Shell shape and meat condition in selectively bred Sydney rock oysters,Saccostrea glomerata (Gould, 1850): The influence of grow‐out methods

The Australian edible oyster industry has been severely impacted by disease and declining yields since the 1970s. Selective breeding of Saccostrea glomerata is one measure addressing these problems by producing fast‐growing, disease‐resistant oysters. Farmers report that selected oysters have different growth characteristics than their wild counterparts using conventional grow‐out methods. This study investigated how different grow‐out methods influence commercially valuable oyster characteristics including shell length, shape, surface growth deformities and meat condition. In June 2015, selectively bred S. glomerata spat were deployed in two estuaries (Hawkesbury River and Georges River) in NSW, Australia, using three grow‐out methods (fixed trays, Stanway cylinders and floating baskets). In November 2015, oysters were transferred among grow‐out methods to test for the effects of changing grow‐out methods on oyster growth patterns. Oysters transferred from baskets to cylinders and from trays to cylinders had, on average, deeper and wider shells, a higher meat condition and fewer shell surface deformities than oysters in other grow‐out method combinations. However, these oysters were smaller than oysters not grown in cylinders. While there were some differences in growth patterns between the estuaries, overall it was the grow‐out methods that most influenced oyster characteristics. This was attributed to differences in the amount and magnitude of movement oysters experienced in the grow‐out methods, as recorded by motion sensors. This study demonstrates how grow‐out methods can be managed to achieve desired growth trajectories and therefore improve marketability among selective bred S. glomerata.     

Seabed habitat mapping in the Kent Group of islands and its role in Marine protected area planning

• 1. Mapping of seabed habitats is increasingly being used to identify the distribution and structure of marine ecosystems and as surrogate measures of biodiversity for marine protected area (MPA) planning. In this study, the distribution of seabed habitats to the 3 nmi limit around the Kent Group of islands, south‐eastern Australia were mapped using video ground‐truthed single‐beam acoustics at the mesoscale level (10 m to 1 km) as part of an MPA planning process.
• 2. Six distinct seabed habitat types (continuous reef, patchy reef, sand, hard sand, sparse sponge, and seagrass) were identified based primarily on visual differences in the first and second echo and a further four (low, medium and high profile reef, and sand hills) on variations in seabed profile identified in the echogram. Extensive acoustic and video transects allowed an estimate of the broad‐scale spatial distribution of seabed habitats defined at several hierarchical levels and provided information on the cover of the dominant benthic species or assemblages.
• 3. The island group supports a range of consolidated habitats, including rocky reefs of varying profile dominated by the macroalgae Phyllospora comosa and Ecklonia radiata in depths down to around 45 m, adjacent to deeper sponge‐dominated reefs containing encrusting, erect and branching forms. Unconsolidated habitats occurred broadly through the island group, with the offshore region dominated by hard sand (sand with scallop shells and/or shell grit) and sparse sponge‐habitats (sand interspersed with low cover of sponge‐dominated assemblages). The sheltered coves were dominated by sand and seagrass habitats consisting of beds of the seagrasses Halophila australis, Zostera tasmanica and Posidonia australis, with variations in species composition, patchiness and percentage cover evident within and between coves.
• 4. In February 2004 the Kent Group MPA was announced, covering all waters out to the 3 nmi limit containing two areas defined as a Sanctuary Zone (‘no take’) and a Habitat Protection Zone (‘restricted take’). Overall, seabed habitat mapping generated a capability to define the boundary and size of potential MPA zones within the Kent Group of islands and was an essential component of the planning process to improve the likelihood that the MPA was comprehensive, adequate and representative (CAR).
• 5. The need to define habitats at multiple scales within a hierarchical classification scheme that are meaningful in terms of biodiversity and CAR principles and identifiable using mapping techniques is discussed.

Copyright © 2004 John Wiley & Sons, Ltd.     

Comparing estimates of number of breeders Nb based on microsatellites and single nucleotide polymorphism of three groups of brown trout (Salmo trutta L.)

Microsatellites (10 MSs) and single nucleotide polymorphism (3871 SNPs) were analysed in three closely related, single‐cohort groups of brown trout, Salmo trutta L. Autumn (W/0+) and subsequent year (W/1+) samples of brown trout of the same stream were retrieved using electric fishing, and one sample of artificially reared brown trout (H/1+), bred from wild parents, was collected from a hatchery. The number of breeders, N_b, was estimated based on each total sample set and from subsets of loci by means of the software LDNe, and by means of Colony2, NeEstimator and ONeSAMP softwares. MS‐based estimates were consequently higher than those based on SNPs. ML‐Relate and Colony2 software was used to estimate putative full‐sib pairs, and there was considerable variation between methods. For monitoring species and populations, both methods are recommended, but to compare N_b across samples and years, the same markers of MSs or SNPs must be used as estimates varied across markers within sample.     

The predation of trumpet shell, Charonia sp., on eight different marine invertebrate species

In this study, predation of the trumpet shell, Charonia sp., on different invertebrate prey species, e.g. starfish, Asterina pectinifera and Asterias amurensis, abalone Haliotis discus hannai, clam Anadara broughtonii and Tapes phillipiarum, and sea urchin Hemicentrotus pulcherrimus and Anthocidaris crassispina, was measured in a laboratory experiment. Each prey species was placed in a tank with a trumpet shell; prey species were not combined. Each combination of prey and trumpet shell was replicated three times. Trumpet shells did not prey on economically important shellfishes, including Anadara broughtonii, Tapes phillipiarum and Haliotis discus hannai. Sea stars were most preferred by the trumpet shell. The following preference gradient from most to least preferred was found: sea stars > sea cucumber > sea urchin. In selected situations, trumpet shells may be a means of biological control of predators of economically important shellfish.     

Integrating recreational fisheries data into stock assessment: implications for model performance and subsequent harvest strategies

Understanding the impacts of recreational fishing on commercially fished stocks is becoming increasingly relevant for fisheries managers. However, data from recreational fisheries are not commonly included in stock assessments of commercially fished stocks. Simulation models of two assessment methods employed in Australia's Commonwealth fisheries were used to explore how recreational fishery data can be included, and the likely consequences for management. In a data‐poor management strategy for blue eye trevalla, Hyperoglyphe antarctica (Carmichael), temporal trends in recreational catch most affected management outcomes. In a data‐rich age‐structured stock assessment for striped marlin, Kajikia audax (Philippi), estimates of stock status were biased when recreational catches were large or when the recreational fishery targeted different size classes than the commercial fishery and these data were not integrated into the assessment. Including data from recreational fishing can change perceptions of stock status and impact recommendations for harvest strategies and management action. An understanding of recreational fishery dynamics should be prioritised for some species.     

Ranking and classification of fishing areas using fuzzy models and techniques

Abstract Fuzzy‐logic‐based methods and fuzzy logic formalism have been demonstrated as appropriate to address the uncertainty and subjectivity in complex environmental problems. This study investigates the use of three fuzzy logic methods in fisheries analysis, aiming towards the grouping and ranking of fishing subareas, according to their fisheries yield. Initially, a simple fuzzy c‐means clustering model was applied to the fishing subareas examined. A rule‐based Mamdani‐type fuzzy inference system was then developed to allow the direct fishing subarea classification. Finally, a species‐economic value weighted global fuzzy membership model was introduced, serving as an indirect classification and ranking scheme. Global memberships were plotted on simple ternary diagrams, producing representations that serve as tools in fisheries management. All methods examined the performance of the Greek fishing subareas, based on the annual landings series of the 10 most abundant fish species in terms of landed biomass, during the period 1985–1999.     

Recovery potential of smalltooth sawfish,Pristis pectinata,in the United States determined using population viability models

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Morpho‐demographic traits of two maërl‐forming algae in beds with different depths and fishing histories

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Identification of a microsatellite marker that is completely linked to shell colour in small abalone,Haliotis diversicolor

A novel orange shell colour has been discovered in small abalone, Haliotis diversicolor (Reeve, 1846). To facilitate and accelerate a selective breeding programme for orange shell colour, a microsatellite marker that was completely linked to the shell colour gene was identified using a selective DNA pool approach and was verified in 448 individuals. Two DNA pools were constructed by pooling equal amounts of genomic DNA from 74 individuals with dark‐brown shells and 87 individuals with orange shells. Approximately 12 of 308 microsatellite markers that were linked to the shell colour gene were isolated using the selective DNA pooling method. After verification in 32 individuals with dark shells and 32 individuals with orange shells, only the Hdi3‐119 locus remained tightly linked to the shell colour gene. Finally, four families were used to verify the accuracy of the Hdi3‐119 locus. All of the individuals with orange shells in the four families harboured a unique 381‐bp allele in marker Hdi3‐119. This marker could be used for selective breeding of orange small abalone.     

Comparing the utility of fishery‐independent and fishery‐dependent methods in assessing the relative abundance of estuarine fish species in partial protection areas

In partial protection management areas such as Recreational Fishing Havens (RFHs) where commercial fishing is prohibited there are fewer sampling methods available for quantifying the relative abundance of species. Consequently, a framework is needed in such areas to decide whether sampling should be based on: (1) fishery‐independent techniques; (2) fishery‐dependent methods that rely on recreational fishery harvests; or (3) a combination of the two. This study compared fishery‐independent data derived from baited remote underwater video stations (BRUVS) and independent fishing surveys (IFS) with fishery‐dependent data based on recreational angler surveys (AS) to identify the fish species that were best enumerated by each method in two Australian RFHs. Each method captured/detected disparate species and each consistently showed correlations with the relative abundance of particular suites of species. The species that were correlated with and best enumerated by BRUVS were Microcanthus strigatus (Cuvier) and Pelates sexlineatus (Qouy & Gaimard); those correlated with IFS were Gerres subfasciatus Cuvier, Girella tricuspidata (Qouy & Gaimard), Mugil cephalus L. and Pomatomus saltatrix (L.); and those correlated with AS were Platycephalus fuscus Cuvier and Acanthopagrus australis (Owen). By identifying the species that were best quantified by each method, this study facilitates accurate monitoring of key species within RFHs.     

Confidence intervals on catch estimates from a recreational fishing survey: a comparison of bootstrap methods

Bootstrap methods are often used for confidence intervals on recreational fish catch estimates, because they are relatively robust and straightforward to implement. Such data are typically highly skewed and zero‐inflated, presenting difficulties for many estimation methods. However, bootstrap performance in many situations is not well understood. Inaccurate confidence intervals can cause management errors, and biased intervals can promote errors in one direction. Although the analyses originate from recreational fisheries data, the conclusions are generally applicable to similarly distributed data from other sources. Using simulation, non‐parametric bootstrap confidence intervals (bootstrap normal, bootstrap percentile, hybrid, bootstrap‐t, BC, and BCa) on catch rate and total catch estimates from a recreational fishing survey were compared. The intervals' coverage (proportion of times the ‘true’ mean fell within the confidence intervals) and relative bias were also compared. The bootstrap‐t, using a resample size of slightly less than n/2, provided confidence intervals with the most correct coverage for both parameters. Intervals were biased, usually substantially, for all other methods, with the commonly used bootstrap percentile among the more biased methods.     

Effects of diets on the growth performance and shell pigmentation of Pacific abalone

This study investigated the effects of natural and artificial diets on growth performance and shell pigmentation of cultured abalone. A 7‐month feeding trial was conducted on 12 000 Pacific abalones (Haliotis discus hannai) with four diets including two extruder‐processed test diets (with & without addition of oleopaprika carotenoids), Pacific dulse (Palmaria mollis) and a combination of Pacific dulse and a test diet. The results showed that the two test diets resulted in higher survival of abalone, but with a lower growth rates when compared with Pacific dulse alone (P < 0.05). The combination diet achieved the highest survival and growth rates. The Pacific dulse resulted in abalone with dark‐brown shells, which are preferred by Asian markets. The test diets led to 52% and 55% of the animals with pink coloured shells and the supplementation of oleopaprika did not affect shell pigmentation. The aqueous acidic extracts from both dark‐brown and pink shells showed blue colour; HPLC‐MS chromatography revealed that the pigments in the extracts were consistent with a biliverdin and a cysteine‐biliverdin. These results are valuable for the development of abalone feed and the control of abalone shell colouration.     

Sponge morphological diversity: a qualitative predictor of species diversity?

1. To the non‐specialist, problems are often associated with the quantification of sponge species diversity, as colour, shape and size can be highly variable within a single species. These variables can lead to an under‐estimation of the contribution of sponges to the biodiversity of the benthos especially during biological surveys. 2. Sponge species diversity (Shannon H′ values), richness (mean number of species) and morphological diversity (Shannon H′ values) were sampled at six sites (6 m depth intervals) on vertical (90°) and inclined surfaces (45°) experiencing different flow regimes at Lough Hyne Marine Nature Reserve (Ireland). Morphological diversity was sampled independently of species diversity. The time taken for the collection of both species and morphological diversity was recorded. 3. Morphological diversity was positively correlated with both sponge species diversity (r²=0.87, p<0.05) and sponge species richness (r²=0.70, p<0.05). Linear regression was found to be significant for both the relationships (p<0.05 for each F‐value). A sigmoidal relationship (r²=0.97, p<0.05) was found between morphological and species richness which proved to be significant (F‐value 40.67, p<0.05). Separate Bray–Curtis dendrograms and correspondence analysis of morphological and species community compositions at the six sites showed very similar clustering and four major clusters were identified. 4. The results of the present study indicate that sampling of sponge morphological diversity, rather than sponge species diversity and richness may be used as a qualitative estimate of sponge species diversity. Sampling of morphological diversity is much less time consuming, both in the field and laboratory, than collecting species diversity data and no specialist knowledge is required. Consideration is given to the use of such relationships in biological surveys and bio‐monitoring. Copyright © 2001 John Wiley & Sons, Ltd.