Artificial Habitats for Fisheries Enhancement in the Australian Region

This paper outlines developments over about 20 years in the construction of and ecological research on artificial reefs, fish aggregation devices (FAD's), and other artificial habitats designed to enhance fish populations and fisheries in the Australian region (including New Zealand and Papua New Guinea). Work was initially carried out on multicomponent reefs using a variety of waste materials, as well as some specially constructed concrete and steel structures. Later studies concentrated on single-component reefs, again mainly using waste materials. Although no definitive conclusions were reached on the relative effectiveness of the different materials used, waste motor vehicle tires and derelict ships were generally judged to be the best all-around materials for single-component reef construction in sheltered estuarine and offshore marine environments, respectively, in this region. FAD's comprising polyvinylchloride pipe sparbuoys (or in some areas polyurethane foam floats) attached to railroad car wheel anchors by polyethylene rope and chain, and supporting attractor drapes of synthetic mesh webbing, also provedtobegenerallysuccessfulin thisarea. Overall conclusions for the Australian region include the predominant use of waste materials in artificial reef construction, which has been primarily aimed at recreational fisheries enhancement; the successful use of FAD's for both recreational and commercial fisheries enhancement; the need for further and better planned research into and monitoring of the effectiveness of both of these enhancement methods; and the need for future research into the effectiveness of unfished "artificial habitat reserves" in enhancing fisheries production from surrounding fished areas.

Contribución de las comunidades bentónicas en la dieta del róbalo (Eleginops maclovinus) en la Ría Deseado (Santa Cruz, Argentina)

Se analiza el aporte de la comunidad bentónica de la ría Deseado a la dieta del róbalo (Eleginops maclovinus), para contribuir al conocimiento de la trama alimentaria costera en la Patagonia austral. Entre la primavera 2005 y otoño 2006 se estudiaron las comunidades bentónicas submareales en áreas de pesca de E. maclovinus y paralelamente, se analizaron los contenidos alimentarios estomacales de róbalos provenientes de la pesca deportiva. La comunidad bentónica de planicies areno-fangosas fue dominada por poliquetos, representados principalmente por las familias Onuphidae, Orbiniidae y Maldanidae. Los crustáceos constituyeron el segundo grupo en importancia y estuvieron representados principalmente por los anfípodos gamáridos Heterophoxus sp. y Ampelisca sp. La comunidad submareal de fondos de rodados estuvo dominada por poliquetos de las familias Nereididae, Cirratulidae y Polynoidae, y los moluscos Perumytilus purpuratus y Margarites violacea. E. maclovinus presentó una dieta bentónica de tipo oportunista y generalista, con una tendencia hacia la ingesta de anfípodos gamáridos y algas clorofíceas. Durante la marea baja, la mayor contribución a su dieta la realizó la comunidad de planicies areno-fangosas submareales. Durante la marea alta, E. maclovinus se alimentó también en el intermareal rocoso, donde preda preferentemente las clorofíceas Enteromorpha spp. ENGLISH: The role of the benthic communities at Ría Deseado in the diet of the Patagonian blenny (Eleginops maclovinus) was analyzed in order to increase the understanding of the coastal food web in southern Patagonia. Subtidal benthic communities were surveyed between spring 2005 and autumn 2006 in areas of E. maclovinus sport fishing. Simultaneously, the stomach contents of patagonian blenny specimens caught during sport fishing were analyzed. The benthic community over flat sandy-muddy bottoms was dominated by polychaetes, mainly from the families Onuphidae, Orbiniidae and Maldanidae, followed by crustaceans, which were mainly represented by the gammarid amphipods Heterophoxus sp. and Ampelisca sp. The subtidal benthic community over pebbly bottoms was dominated by polychaetes from the families Nereididae, Cirratulidae and Polynoidae and the mollusks Perumytilus purpuratus and Margarites violacea. The diet of E. maclovinus was benthic opportunist and generalist, with a preference to feed on gammarid amphipods and chlorophycea algae. During low tide, the main dietary contribution came from the subtidal community over flat sandy-muddy bottoms whereas, during high tide, E. maclovinus also preyed on rocky intertidal species, mainly the Chlorophycea Enteromorpha spp.

Life history and production of Capitella capitata (Polychaeta: Capitellidae) in Río de la Plata Estuary (Argentina)

A benthic survey was carried out from November 1998 to December 1999 in the tidal flats of Bahía Samborombón (Río de la Plata estuary, Argentina), in order to study the population structure, reproductive aspects, growth and secondary production of Capitella capitata (Fabricius, 1780). Growth was analyzed using ELEFAN routine, and the secondary production was estimated by Hynes and Coleman's method (1968). C. capitata did not present periods of very important recruitments throughout the year; however, the abundance of smallest size classes was higher during summer and autumn. The summer cohort showed a growth rate (K) of 2.05 and a seasonal growth oscillation (C) of 0.6, pointing out that worms grew very slowly during winter months. The life span of this cohort was 13 months. The autumn cohort showed a lower growth rate (K= 1.5) and its growth was lowest during winter. The life span was 15 months for this cohort. C. capitata in Punta Rasa presented an extended reproductive period, with absence of activity during winter months. The type of eggs and larvae suggest that C. capitata has benthic larval development in the study area, destining its reproductive effort to the production of a low number of eggs, and assuring larvae survival through incubation in brooding tubes. The annual mean biomass in Punta Rasa was 0.117 g m-2 (AFDW), with a mean secondary production of 0.23 g m-2 y-1 and a P/B ratio of 1.96 y-1. The relatively low density, biomass production and P/B ratio of C. capitata in Punta Rasa can be considered as reference values for this species inhabiting undisturbed or moderately disturbed areas.

El alga invasora Undaria pinnatifida (Harvey) Suringar en la Ría Deseado (Patagonia austral, Argentina): ciclo del esporofito y factores ambientales determinantes de su distribución

Undaria pinnatifida was registered in Ría Deseado (47º45´S, 65º55´W _ southern Patagonia) by the first time in spring 2005, colonizing the intertidal and shallow subtidal. A seasonal survey in 2006 showed that U. pinnatifida was established in a sheltered zone inside the estuary, along a coastal fringe of 8 km between Punta Cascajo and Cañadón del Puerto. This continuous distribution was only interrupted in the mouth of canyons that flow into Ría Deseado, where the bottom is conformed by mud and sand. The sporophytes were mainly found colonizing the rocky bottom in the lower intertidal, bordering the Macrocystis pyrifera population. The highest density and biomass of sporophytes (12.13 ind. m-2; 254.60 g m-2) were registered during spring, when the population was mainly conformed by individuals of medium sizes. The lowest density and biomass (0.33 ind. m-2; 5.69 g m-2) were registered in autumn. Juvenile sporophytes recruited throughout the year, but presented the highest percentage in the population during autumn and winter. First mature sporophytes appeared in spring and attained their maximum size in summer. After this, the sprophytes decayed and disappeared. Environmental factors such as rocky bottoms availability and water transparency may be the main factors determining the sporophytes distribution in Ría Deseado. The field experiment point out that M. pyrifera population is an important factor controlling the dispersion of U. pinnatifida towards the subtidal. SPANISH: Undaria pinnatifida fue registrada en la Ría Deseado (47º45´ S, 65º55´ W _ Patagonia austral) durante la primavera de 2005, colonizando el intermareal y submareal somero. Los relevamientos estacionales realizados durante el 2006, revelaron que U. pinnatifida se encontró establecida en una zona protegida en el interior de la ría, ocupando una franja costera de aproximadamente 8 km de largo entre Punta Cascajo y el Cañadón del Puerto. Esta distribución casi continua sólo presentó algunas interrupciones en la boca de los cañadones que desembocan en la ría, donde el fondo predominante es de tipo areno-fangoso. Los esporofitos de U. pinnatifida ocuparon preferentemente el fondo rocoso del intermareal inferior, limitando con la población de Macrocystis pyrifera. La densidad y biomasa más altas de esporofitos (12,13 ind. m-2; 254,60 g m-2) fueron registradas en primavera, cuando la población se encontró compuesta principalmente por individuos de tallas intermedias. La densidad y biomasa más bajas (0,33 ind. m-2; 5,69 g m-2) fueron registradas durante el otoño. Los esporofitos juveniles se reclutaron a lo largo de todo el año, pero alcanzaron su mayor proporción en la población durante el otoño y el invierno. Los esporofitos reproductivamente maduros aparecieron durante la primavera y alcanzaron su talla máxima durante el verano, luego del cual comenzaron a deteriorarse y a desaparecer. Factores como la disponibilidad de fondos rocosos y la transparencia de las aguas podrían actuar como los principales factores determinantes de su distribución en la ría. El experimento de campo realizado revela que los bosques de M. pyrifera actúan también como un importante factor de control, limitando la dispersión de U. pinnatifida hacia el submareal.

Accumulation of Heavy Metals in Franciscanas from Buenos Aires Province, Argentina

Marine mammals accumulate heavy metals in their tissues at different concentrations according to trophic levels and environmental conditions. The franciscana (Pontoporia blainvillei) is a small coastal species inhabiting the marine and estuarine areas of the Southwestern Atlantic Ocean. Its diet includes numerous species of small fish, squid and crustaceans. The aims of this study were to (i) assess the heavy metal concentration and burden distribution in different franciscana age classes and sex, and to (ii) evaluate both the accumulation processes and the transplacental transference of zinc, cadmium, copper and total mercury. Heavy metal concentrations (wet weight) were determined in eighteen dolphins by Atomic Absorption Spectrophotometry (AAS), by the cold vapour technique (mercury) or with air/acetylene flame (cadmium, zinc and copper). Liver showed the highest concentrations of mercury (max. 8.8 mg/g), zinc (max. 29.7 mg/g) and copper (max. 19.0 mg/g), whereas the highest cadmium concentrations (max. 6.7 mg/g) were found in kidney. Adults contained the highest concentrations for all heavy metals, followed by juveniles and calves in decreasing order, suggesting an age-related accumulation. No differences (p<0.05) were found between sexes within each age class. Organ burden distribution followed the same pattern for all metals and age classes: liver tissues contained maximum burdens. Mercury concentrations were higher than those of cadmium in both foetuses and newborns; and neither metal could be detected in the foetus. The analysed data suggested differences in the placental transference between metals, being significant for mercury and almost null in the case of cadmium. We can conclude that franciscana accumulates heavy metals and, due to its coastal distribution, it may be considered as a biomonitor of its environment. SPANISH: Los mamíferos marinos acumulan metales pesados en sus tejidos cuyas concentraciones están en relación con su nivel trófico y las condiciones ambientales. La franciscana (Pontoporia blainvillei) es una especie costera que habita áreas marinas y estuariales en el Atlántico Sudoccidental. Su dieta está constituída por peces, como item alimentario principal, calamares y crustáceos. El objetivo del presente trabajo es estudiar la distribución de metales pesados en diferentes clases de edad y en ambos sexos, evaluando procesos de acumulación y cargas de cadmio, mercurio total, cinc y cobre. Las concentraciones de metales pesados (en peso húmedo) fueron determinadas en dieciocho delfines por Espectrofotometría de Absorción Atómica (EAA), usando la técnica de vapor frío (mercurio) o llama de aire/acetileno (cadmio, cinc y cobre). El hígado presentó las concentraciones más altas de mercurio (máx. 8,8 mg/g), cinc (máx. 29,7 mg/g) y cobre (máx. 19,0 mg/g), mientras que las más altas de cadmio (máx. 6,7 mg/g) fueron encontradas en el riñón. Los adultos presentaron los niveles más altos, presentando los juveniles y cachorros concentraciones menores, lo cual sugirió una acumulación con la edad. No se encontraron diferencias significativas (p < 0,05) entre sexos dentro de cada clase de edad. Las cargas de metales pesados en los órganos presentaron la misma disribución para todos los metales y clases de edad. Los valores más altos fueron encontrados en el hígado, incluyendo los correspondientes a cadmio. Las concentraciones de mercurio y cadmio fueron no detectables en el feto, mientras que las de mercurio fueron superiores a las de cadmio en los cachorros. Los datos encontrados en el feto sugieren una transferencia nula a través de la placenta. Podemos concluir que P.blainvillei acumula metales pesados en sus tejidos y debido a su distribución costera, esta especie puede ser considerada como un biomonitor de su ambiente.