A comparative analysis of habitat quality between artificial and natural creeks in the Mediterranean killifish Aphanius fasciatus

1. In transitional water ecosystems, habitat loss is one of the major threats to fish biodiversity. This is particularly true in the case of temperate salt marshes. Good quality artificial novel habitats may compensate for the loss of natural habitats, acting as a refuge for fish populations. 2. The aim of this study was to use coloured ornamental traits exhibited by the males of a small lagoon-resident fish, the Mediterranean killifish Aphanius fasciatus (Valenciennes, 1821), to assess habitat quality in both the natural and artificial creeks of the Venice lagoon. 3. The conspicuousness of two secondary sexual traits, the yellow/orange caudal fin pigmentation and the contrast between white and dark vertical bars on body sides, proved to be greater in artificial habitats compared to natural salt marshes, highlighting the refuge function of artificial creeks. 4. The use of secondary sexual traits could be extended to other fish species and to other aquatic habitats as a non-invasive approach. This would allow the identification of good quality habitats in the context of fish population management and conservation

Monitoramento de fitoplâncton e microcistina no reservatório da UHE Americana Monitoring phytoplankton and microcistyn at the Americana reservoir

Este trabalho foi realizado na UHE Americana, pertencente à Companhia Paulista de Força e Luz, e faz parte de um projeto de pesquisa e desenvolvimento realizado em conjunto com a Faculdade de Ciências Agronômicas - UNESP, de Botucatu. As amostragens de água foram realizadas nos meses de fevereiro, abril, junho e outubro de 2004. As características analisadas foram: temperatura da água, pH, oxigênio dissolvido, condutividade, nitrogênio total, nitrito, nitrato, amônia, fósforo total, fosfato, fosfato inorgânico, juntamente com análise qualitativa e quantitativa da comunidade fitoplanctônica e a toxicidade. O reservatório apresentou valores elevados de fósforo total, variando de 18 a 509 µg L-1; fosfato, de 4 a 463 µg L-1; nitrogênio total, de 0,99 a 17,25 mg L-1; e nitrato, de 0,26 a 15,29 mg L-1. Para a comunidade fitoplanctônica foram encontrados 103 táxons em todo o período amostrado; a maior riqueza foi encontrada no ponto P06, e a maior pobreza de táxons, nos pontos localizadas no corpo central do reservatório (P02, P03, P04 e P05). A maior concentração de cianofícea ocorreu em abril de 2004: 5.375.175 ind. L-1. As espécies que apresentaram as maiores densidades foram Microcystis aeruginosa, Anabaena spiroides, Microcystis sp. e Pseudoanabaena mucicola; a maior densidade foi apresentada por Anabaena spiroides, com 4.178.084 ind. L-1. Nos meses de junho e outubro a classe Cryptophyceae teve uma grande contribuição para a densidade total. Apesar da grande densidade de cianobactérias, os valores de toxicidade ficaram abaixo do limite permitido pela Portaria nº 1.469.<br>This work was carried out at the Americana Reservoir, owned by Companhia Paulista de Força e Luz, and was part of a joint R&D project with Faculdade de Ciências Agronômicas - Botucatu - São Paulo - Brazil. Water sampling was collected in February, April, June and October 2004. The following characteristics were analyzed: water temperature, pH, dissolved oxygen, conductivity, total nitrogen, nitrite, nitrate, ammonia, total phosphorus, inorganic phosphate, as well as qualitative and quantitative analysis of phytoplankton and toxicity. The reservoir showed high levels of total phosphorus, ranging from 18 to 509 µg L-1; phosphate, 4 to 463 µg L-1; total nitrogen, 0.99 to 17.25 mg L-1; nitrate, 0.26 to 15.29 mg L-1. For the phytoplankton community, 103 taxa were found during the sampled period, with the greatest richness being found at point P06 and the poorest at the center of the reservoir (P02, P03, P04 and P05). The highest concentration of cyanophyceae was observed on April 2004, 5.375.175 un. L-1. The species presenting higher densities were Microcystis aeruginosa, Anabaena spiroides, Microcystis sp and Pseudoanabaena mucicola, with Anabaena spiroides presenting the highest density of all, 4.178.084 un. L-1. In July and October, the Cryptophyceae class made a large contribution to total density. Despite the great density of Cyanobacteria, toxicity values were below the limit allowed by Ruling number 1.469

Limnological variability and pelagic fish abundance (Stolothrissa tanganicae and Lates stappersii) in Lake Tanganyika

The abundance of two main pelagic fish species in Lake Tanganyika (Stolothrissa tanganicae and Lates stappersii) has always been observed to fluctuate considerably at different time scales. The inverse correlation between the abundance of these species has often been interpreted as the consequence of predator-prey relations (avoidance behaviour by the prey). However, currently the two species often appear spatially segregated in the lake, S. tanganicae dominating in the north while L. stappersii is generally abundant in the south where it feeds mostly on shrimps. A fluctuating abundance of the species is nevertheless observed. As these fish species have a major importance for the fisheries, we investigated the limnological variability in relation to the short-term variability of fish catches. The abundance of S. tanganicae was positively correlated to plankton biomass (r = 0.65), while water transparency (r = 0.56), depth of mixed layer (r = -0.70) and oxygenated water appeared important drivers for the abundance of L. stappersii. Alternating "mixing" and "stable" states of the epilimnion related to seasonal and internal waves variability are probably determinant for the short-term variability in abundance of S. tanganicae and L. stappersii. In the framework of this study, remote sensing has shown a potentially interesting application for fisheries research at Lake Tanganyika. We observed a close correspondence between phytoplankton blooms at the time of trade winds changes and increased catches of S. tanganicae in the south. The anti-correlated abundance of S. tanganicae and L. stappersii probably mainly reflects the underlying fluctuating limnological environment. Fisheries studies need to integrate limnological and planktonic monitoring to better understand large and complex ecosystems such as Lake Tanganyika