Macroinvertebrate sampling techniques for streams in semi-arid regions : comparison of the Surber method and a unit-effort traveling kick method /

Bibliography: p. 20-21.

Measuring the capacitance per unit length of biconical structures of arbitrary cross section /

"Contract No. AF33(616)-3220 Project No. 6(7-4600) Task 40572 Wright Air Development Center"

Effects of marine reserve protection on the mud crap Scylla serrata in a sex-biased fishery in subtropical Australia

The impact of sex-biased fishing and marine reserve protection on the mud crab Scylla serrata was examined by comparing the catch rates (catch-per-unit-effort, CPUE), mean size, sex ratios and movement of crabs in 2 coastal marine reserves (1.9 and 5.7 km(2)) and 4 fished non-reserve sites in subtropical Australia. Five years after closure, both marine reserves supported higher catch rates and a larger mean size of S. serrata than non-reserve sites. Males dominated catches of S. serrata in both marine reserves, where CPUE was at least twice as high within the reserves compared to non-reserve sites. Male crabs were also 10% larger in the reserves compared to adjacent fished areas, and of the total male catch, over 70% were equal to or greater than legal size compared to less than 50% outside the reserves. The sex ratio of S. serrata was skewed towards females in all nonreserve sites, which was most likely a result of the ban on taking female S. serrata in Moreton Bay. As only male crabs of >= 15 cm CW made up the S. serrata fishery in Moreton Bay, sex ratios of mature male and female crabs were examined, revealing a strong skew (2:1) towards mature males in both marine reserves. Of the 472 S. serrata captured in this study, 338 were tagged in the reserves in order to document movement of the crabs between the reserve and non-reserve sites. Of the 37 recaptured crabs, 73% were recorded inside the reserves, with some spillover (i.e. cross-boundary movement) of crabs recorded in fished areas. This study demonstrates the effectiveness of small (< 6 km(2)) marine reserves for sex-biased exploited fisheries species.

Effect of rainfall as a component of climate change on estuarine fish production in Queensland, Australia

The speculation that climate change may impact on sustainable fish production suggests a need to understand how these effects influence fish catch on a broad scale. With a gross annual value of A$ 2.2 billion, the fishing industry is a significant primary industry in Australia. Many commercially important fish species use estuarine habitats such as mangroves, tidal flats and seagrass beds as nurseries or breeding grounds and have lifecycles correlated to rainfall and temperature patterns. Correlation of catches of mullet (e.g. Mugil cephalus) and barramundi (Lates calcarifer) with rainfall suggests that fisheries may be sensitive to effects of climate change. This work reviews key commercial fish and crustacean species and their link to estuaries and climate parameters. A conceptual model demonstrates ecological and biophysical links of estuarine habitats that influences capture fisheries production. The difficulty involved in explaining the effect of climate change on fisheries arising from the lack of ecological knowledge may be overcome by relating climate parameters with long-term fish catch data. Catch per unit effort (CPUE), rainfall, the Southern Oscillation Index (SOI) and catch time series for specific combinations of climate seasons and regions have been explored and surplus production models applied to Queensland's commercial fish catch data with the program CLIMPROD. Results indicate that up to 30% of Queensland's total fish catch and up to 80% of the barramundi catch variation for specific regions can be explained by rainfall often with a lagged response to rainfall events. Our approach allows an evaluation of the economic consequences of climate parameters on estuarine fisheries. thus highlighting the need to develop forecast models and manage estuaries for future climate chan e impact by adjusting the quota for climate change sensitive species. Different modelling approaches are discussed with respect to their forecast ability. (c) 2006 Elsevier Ltd. All rights reserved.

Segregation of Palaemonid Shrimp Along an Everglades Estuarine Gradient: Do Multiple Species Have Similar Trophic Function?

Variation in physical gradients and production along estuaries can alter species compositions. Spatiotemporal variation in abundance and distribution of palaemonid shrimp species was investigated in relation to seasonal freshwater inputs and salinity in the Shark River Estuary, Everglades National Park, Florida, USA. Using trapping techniques, multiple sites were sampled repeatedly extending from the headwaters to the Gulf of Mexico. Stable isotope analyses were also performed on a subset of samples. Five palaemonid species occurred in the samples: Palaemonetes paludosus (Gibbes, 1850), Palaemonetes pugio (Holthuis, 1949), Palaemonetes intermedius (Holthuis, 1949), Palaemon floridanus (Chace, 1942), and Leander paulensis(Ortmann, 1897). Overall, shrimp catches in traps doubled in the dry season. Catches in the upper estuary were dominated by P.paludosus, particularly in the wet season, while catch per unit effort at the most downstream and highest salinity sites were dominated by P. floridanus. At mid-estuary, several species co-occurred. δ15n analyses revealed that most species filled similar roles in the community, with the exception of P. paludosus, which shifted from enrichment in the dry season to depletion in the wet season as it expanded downstream in the estuary. Palaemonid δ13C values varied between sites and seasons, with shrimp in upstream sites being more depleted. These data suggest that changes in salinity regimes resulting from Everglades restoration efforts may result in species replacement, with potential implications for trophic dynamics.

Influence of teleost abundance on the distribution and abundance of sharks in Florida Bay, USA

Understanding the factors that influence the distribution and abundance of predators, including sharks, is important for predicting the impacts of human changes to the environment. Such studies are particularly important in Florida Bay, USA where there are planned large-scale changes to patterns of freshwater input from the Everglades ecosystem. Studies of many marine predators suggest that links between predator and prey habitat use may vary with spatial scale, but there have been few studies of the role of prey distribution in shaping habitat use and abundance of sharks. We used longline catches of sharks and trawls for potential teleost prey to determine the influence of teleost abundance on shark abundance at the scale of regions and habitats in Florida Bay. We found that shark catch per unit effort (CPUE) was not linked to CPUE ofteleosts at the scale of sampling sites, but shark CPUE was positively correlated with the mean CPUE for teleosts within a region. Although there does not appear to be a strong match between the abundance of teleosts and sharks at small spatial scales, regional shark abundance is likely driven, at least partially, by the availability of prey. Management strategies that influence teleost abundance will have cascading effects to higher trophic levels in Florida Bay.

Gill net selectivity for European hake Merluccius merluccius from southern Portugal: implications for fishery management

A study of European hake Merluccius merluccius gill net selectivity was undertaken off the Algarve (Southern Portugal), between 1999 and 2001. Four nominal mesh sizes (70, 80, 90 and 100 mm) were used in fishing trials and the 'share each length class catch total' (SELECT) method was used to fit gill net selectivity curves. Hake were caught in the same size range by all mesh sizes, between 17 and 65 cm total length. While most fishes were wedged, significant and similar proportions were entangled in all mesh sizes, contributing to the wide size range, and in some cases, bimodal shape of catch size frequency distributions. Insignificant numbers of undersized hake were caught, with most catches consisting of mature female fish. Catch rates decreased sharply with increasing mesh size. The bimodal model gave the best fit for hake that were wedged, with estimated modal lengths of 40.1, 46.7 and 51.0 cm for the 70, 80 and 90 mm nominal mesh sizes, respectively. The high catch per unit effort of the smallest mesh size, with most fish caught being female, together with the fact that the modal length of the fitted selectivity curve is well below the size at maturity for hake in Portuguese waters, suggests that the 80 mm nominal mesh size is more appropriate for ensuring resource sustainability.

Effects of hook and bait on targeted and bycatch fishes in an equatorial atlantic pelagic longline fishery

We examined the effects of different hook style and bait type combinations on the catches of targeted, bycatch, and discarded fishes in equatorial Atlantic waters. In total, 221 longline sets (>305,000 hooks) were deployed from Portuguese pelagic longline vessels (SELECT -PAL Project) during the February–October fishing season. Three different hook styles and two bait types were tested: the traditional J-hook was compared to two circle hooks (one non-offset and one with 10° offset), and squid bait was compared to mackerel. Catch per unit effort (CPU Es) were calculated and compared between the different hook style and bait type combinations, which indicated that the effects of hook style and bait on the CPU Es were species-specific. For example, swordfish CPU Es were higher with J-hooks baited with squid, while for targeted tunas and blue shark only the bait effect was significant, but with opposite effect (i.e., higher catches of tuna with squid bait and higher catches of blue shark with mackerel bait). For the discarded species, at-haulback mortality was also species-specific. Proportions of alive vs dead specimens at time of fishing gear retrieval did not vary significantly by hook style or bait type combinations. The total retained catch was analyzed in value per unit effort (VPU E), and indicated losses in fishery revenue when mackerel was used instead of squid, but not when circle hooks were used instead of J-hooks.

SISTEMA DE INFORMACIÓN GEOGRÁFICA PARA EL ANÁLISIS ESPACIAL DE LA PESQUERÍA ARTESANAL ASENTADA EN LA PENÍNSULA DE ARAYA, ESTADO SUCRE – VENEZUELA

Se desarrolló un Sistema de Información Geográfica (SIG) automatizado para el análisis espacial de las capturas, del esfuerzo pesquero, de la abundancia estimada de especies mediante el índice de Captura por Unidad de Esfuerzo (CPUE) y de su relación con algunos factores ambientales (profundidad, tipo de fondo y temperatura superficial del mar) de la esquería artesanal asentada en la península de Araya, Estado Sucre, República de Venezuela. Este programa automatizado, denominado SIGPAR, fue desarrollado utilizando el lenguaje Microsoft® Visual Basic 6 y la respectiva librería del software SIG Idrisi®, a cuyo menú principal fue agregado un nuevo módulo que facilita la interacción con los usuarios.Palabras claves: Sistema de Información Geográfica (SIG); pesquería artesanal; Península de Araya, Venezuela.AbstractA Geographic Information System (GIS) application software was developed for the spatial analysis of fishing catches, the estimated abundance of species by the Catch per Unit Effort (CPUE) index, and its relationship with various environmental factors (depth, type of bottom, and surface temperature of the sea) of the artisanal fishery based in the Peninsula of Araya, State of Sucre, in Venezuela. This application, named SIGPAR, was developed using Microsoft® Visual Basic 6 and IDRISI®. A menu button was added to the GIS software IDRISI® for convenience of users.Key Words: Geographic Information System (GIS), Artisanal Fisheries, Araya, Venezuela.