Carlos Alberto Borzone

Population structure and reproductive biology of Metamysidopsis neritica (Crustacea: Mysidacea) in a sand beach in south Brazil

Misidaceos sao crustaceos comuns no sublitoral de todo o mundo. Neste estudo as caracteristicas populacionais e a biologia reprodutiva de Metamysidopsis neritica Bond-Buckup & Tavares, 1992 foram estudadas na zona de arrebetacao de uma praia no sul brasileiro (Atami). Os misidaceoa foram coletados mensalmente no periodo de agosto/1999 a julho/2000 (total de 29490 exemplares). Os individuos foram classificados em seis categorias populacionais. A maior abundância ocorreu em maio (8665) e em agosto (6415), e a menor, em setembro (336) e dezembro (368). Foram identificadas tres principais geracoes, nomeadas de geracao do verao, do outono e do inverno. A com maior longevidade foi a do inverno (quatro a cinco meses). A duracao da geracao do outono foi de quatro meses e a do verao variou de tres a quatro meses. Femeas ovigeras foram amostradas durante todo o ano, sendo a maior proporcao obtida em julho. O numero de ovos e de larvas variou de um a 16. Foi observada uma fraca relacao entre o comprimento das femeas e: o numero de ovos, o volume dos ovos e o numero de larvas com e sem olhos. O volume dos ovos aumentou na estacao mais fria, sendo os menores valores registrados no verao. Os resultados sugerem uma possivel relacao direta entre o volume dos ovos e a logevidade das geracoes.

Human impact on the benthic macrofauna of two beach environments with different morphodynamic characteristics in southern Brazil

Pollution, exploitation of resources, erosion and recreational activities produce the most common impacts that somehow alter the natural balance of beach ecosystems. The aim of this study was to compare the richness and abundance of the benthic macrofauna of two sectors, one non-urbanized and the other urbanized, on each of two morphodynamically different beaches. Sectors of each beach were analyzed taking into account morphodynamic, anthropogenic (recreational activities) and ecological aspects. Morphodynamically, one of the beaches presented sediment formed of fine sand with a gentle slope and morphodynamism with dissipative characteristics. The other was of sediment formed of medium sand with a steep profile and of intermediate to reflective morphodynamic characteristics. On both beaches during the summer, the urbanized sector was frequented by a greater number of users than the non-urbanized sector. On the beach with dissipative morphodynamism, negative relationships were observed between user abundance and the species Bledius bonariensis, Donax hanleyanus, Thoracophelia furcifera, Excirolana armata, Phoxocephalopsis sp. and Tholozodium rhombofrontalis. On the beach with intermediate to reflective morphodynamics, low abundances of Atlantorchestoidea brasiliensis and Excirolana braziliensis were recorded in the urbanized sector. Thus the results of this study suggest the use of certain species as indicators of human impacts on beach ecosystems.

Spatial distribution of the Ocypode quadrata (Crustacea: Ocypodidae) along estuarine environments in the Paranaguá Bay Complex, southern Brazil

O presente estudo avalia a distribuicao espacial de Ocypode quadrata Fabricius, 1787 em treze praias estuarinas distribuidas ao longo dos dois principais eixos do complexo estuarino da Baia de Paranagua, sul do Brasil. Em cada praia, a densidade de tocas do caranguejo em tres niveis distribuidos em torno da marca da preamar foi estimada durante os periodos de verao e de inverno. Todas as praias apresentaram uma declividade bem acentuada (2,6 a 8,3o de inclinacao) e a composicao do sedimento variando, em direcao ao interior do estuario, de areia fina bem selecionada a areia grossa muito pobremente selecionada. A salinidade da agua variou entre 31 (proximo a desembocadura da baia) e 14 nas praias estuarinas mais internas. As densidades de tocas de O. quadrata nas praias estuarinas foram similares as registradas para as praias oceânicas. Entretanto, a ausencia de tocas nas quatro praias estuarinas mais internas sugere que a salinidade junto com a penetrabilidade do sedimento possam ser fatores que inibam a ocorrencia desse caranguejo nas regioes superiores do estuario. Entre as outras praias, a densidade de tocas mostrou uma marcada sazonalidade; os baixos valores observados durante o inverno estao provavelmente relacionados a um atraso na atividade dos caranguejos devido as baixas temperaturas durante o comeco das manhas de inverno. A ausencia de um claro padrao de zonacao foi relacionada a particular morfologia das praias estuarinas.

Population dynamics and secondary production of Euzonus furciferus Ehlers (Polychaeta, Opheliidae) in an exposed sandy beach of Southern Brazil

The distribution, population dynamics and secondary production of the polychaete Euzonus furciferus was studied in Atami Beach (Southern Brazil), from February 1992 to March 1993. Euzonus furciferus Ehlers, 1897 is the only deposit feeder species of the upper intertidal region. The organisms were present in the sandy beach all over the year, concentrated in a narrow band, and reaching maximal densities of 3,029 individuals m-2. Peaks of abundance occurred in September 1992, with a mean of 681.8 individuals m-2. Recruitment occurred in winter, with a peak in July. Mean annual biomass was estimated in 0.218 gAFDW m-2, with a total annual production of 0.466 gAFDW m-2 y-1, giving a P/B ratio of 2.13 y-1. Similar values were found for a filter-feeder polychaete inhabiting the same beach, suggesting that general food disposability of each particular environment is more important for production than the trophic strategic employed by those organisms exploring this environment.

Reprodução de Mellita quinquiesperforata (Leske) (Echinodermata, Echinoidea) em dois ecossistemas praiais contrastantes

O ciclo reprodutivo do equinoide irregular Mellita quinquiesperforata (Leske, 1778) foi estudado em populacoes de duas praias com diferentes condicoes morfodinâmicas na costa paranaense, de fevereiro de 1992 a julho de 1994. A gametogenese foi descrita pela analise histologica das gonadas e pela variacao do indice gonadal. Foram encontradas diferencas com relacao a extensao do periodo de estocagem de nutrientes e do periodo de liberacao dos gametas nas populacoes. Ambas exibiram um marcado periodo reprodutivo na primavera e no verao e uma epoca de estocagem de nutrientes no outono e no inverno. Na praia intermediaria-dissipativa a liberacao de gametas ocorreu num periodo menor do que na reflectiva, porem a fase de acumulo de reservas nutritivas foi mais extensa na primeira. O indice gonadal apresentou variacoes entre os sexos e foi influenciado pelas caracteristicas populacionais. As diferentes estrategias na alocacao dos recursos entre manutencao e esforco reprodutivo (tamanho do ovocito) confirmam a elevada plasticidade adaptativa desenvolvida pela especie para habitar ambientes praiais contrastantes

Aspectos da reprodução e dinâmica populacional de Chione pubera (Bory Saint-Vicent) (Bivalvia, Veneridae) no sul do Brasil

Material collected with a 2-meter wide beam trawl during eight surveys conducted from December 1995 to February 1997 was used for a first preliminary description of the reproduction and population dynamics of the edible venerid bivalve Chione pubera (Bory Saint-Vicent, 1827). Greatest catches were found between 30 to 35 meters depth, on fine sandy bottoms with a mud content lower than 10%. Dry weight meat condition index showed highest values during autumn and lowest values from winter to summer months. Histological analysis of gonadal tissue showed a continuous reproduction, with peaks of maturation on autumn and spring, Spawning was related with the increase of water temperature, that occurs twice a year in the region as a consequence of a particular hydrological characteristic of the inner continental shelf. Size frequency distribution showed a unique principal mode with slow if any displacement through time, indicating a long lived species.

Variabilidade da infauna adjacente a estruturas rochosas na plataforma rasa do litoral do Paraná, Brasil

Ocean rocky formations are known as islands. When islands become completely submerged, they are called stone slabs. Like reefs, these formations alter the flux of water produced by the waves, which in turn interacts with the adjacent sediment, altering the sediment and its undulation marks. The alterations caused by the interaction between the waves and emerged or submerged rigid structures can potentially alter the composition and the distributional patterns of the infauna of the adjacent, unconsolidated substrate. In order to evaluate the strength of these alterations, we sampled the infauna and the sediment adjacent to two ocean structures, one emerged and one submerged. Collecting was performed in winter and summer, while discriminating between the faces of the structures, the distances from them, and the troughs and crests of ripple marks. The granulometric characteristics of the sediments and the dimensions of the undulation marks differed in regards to the orientation of and the distance from the structures. Infaunal associations showed differences that can be explained by the sedimentation patterns. However, there were no differences in sediment characteristics and composition of the infauna when troughs and crests were compared. The waves interacted most intensely with the submerged structure, where the sediment showed larger grains next to the undulation marks, what resulted in a more pronounced differentiation of the infauna.

Distribuição dos Myscidacea (Crustácea) em duas praias arenosas com diferente morfodinamismo

The order Mysidacea comprises small and very common crustaceans that inhabit most coastal ecosystem. The present contribution describes the composition, abundance and distribution of mysids in two sandy beaches representing the extreme conditions of the morphodynamics spectrum. Six species of mysids were found at the studied beaches. Metamysidopsis neritica Bond-Buckup & Tavares, 1992 was the most abundant species with more than 97% of the total individuals collected at the two beaches. At the dissipative beach was dominant in the swash and surf zone, with the greater abundance in the inner surf zone. At the reflective beach, this species was extremely abundant in the surf zone and backward the breaker. Bowmaniella brasiliensis Bacescu, 1968 occurred in low density at the surf zone of the dissipative beach, with the greater abundance in the outer surf zone, and it was practically absent in the nearshore zone. We suggest that mysids zonation in sandy beaches may be first developed as a response to food availability patterns imposed by the nearshore circulation systems, and in the second place as a result of competitive exclusion. The suggestion of partitioning of food and spatial resources shown by the mysid species is surprising in view of the apparent physical harshness and low spatial heterogeneity that seem to characterise the beach environment.

The contribution of microphytobenthos for scallop Euvola ziczac (Bivalvia:Pectinidae) feeding in a shallow area of the south-eastern Brazilian continental shelf

The general composition and abundance of microalgae in sediment, water column and stomach contents of scallops were studied at two Euvola ziczac beds on the south-eastern inner Brazilian continental shelf. These areas, which support an extensive demersal fishery, are hydrologically dominated by Tropical and Subantarctic Waters and exhibit a summer water intrusion of South Atlantic Central Water (SACW). The same genera of benthic diatoms, mainly 30 μm and dinoflagellates) was composed of distinct taxa and presented a high seasonal variation in abundance. The prevalence of microphytobenthos in the scallop diet suggests the importance of this community to the sustainability of this valuable demersal fishery resource.

The collapse of the scallop Euvola ziczac (Linnaeus, 1758) (Bivalvia: Pectinidae) fishery in Brazil: changes in distribution and relative abundance after 23 years of exploitation

In Brazil, an industrial trawling fishery directed to Euvola ziczac started in 1973 and collapsed after 1980, when scallop landings reached 8,800 t. Since 1995 E. ziczac landings have not surpassed a few hundred kilograms. Based on surveys carried out in 1974-1975 and in 1995-1996, this work assesses temporal changes occurred in scallop distribution and relative abundance patterns and analyzes the current stock situation under the present management regimes applied to the local demersal trawling fishery. In the 1970s E. ziczac was concentrated in a main bed extending from southern Sao Paulo to northern Santa Catarina States and between 30 and 50 m depth. This pattern changed dramatically during the 1990s, when only two very small and low-density concentrations were found in the region. Cumulative effects of reducing areas and density within the remnant concentrations produced a reduction in the stock biomass of 98%. Management of the local double rig trawler fishery has always focused on its first main target, the shrimps Farfantepenaeus paulensis and F. brasiliensis. Additional measures have not been implemented, even after substantial part of the fleet has directed its effort to alternative shelf and slope resources. The collapse of the Brazilian scallop fishery provides a striking example of irreversible damage caused by uncontrolled fishing redirection allocated to other resources, demonstrating the need of changes in the Brazilian demersal fishery management model.