Recruitment and commercial seed procurement of the blue mussel Mytilus edulis in Maine

A thorough understanding of recruitment in the blue mussel is necessary if the new industry is to maximize seed procurement without impinging upon other fisheries. Larval appearance is a relatively precise event in Maine, cued to early summer water temperature of 10–12 C and, apparently, full moon spawning events. Mussel larvae are more abundant on the flood tides indicating inshore and estuarine retention, although this retention relates to the morphometry and relative energy of the system. Webb Cove, a wide embayment with maximum sample station current velocity of 0.2 m/s, showed a random ebb tide vs. flood tide larval distribution; the narrow, long Damariscotta River estuary with 0.35 m/s current velocity showed a two‐fold flood tide larval enhancement and the Jordan River with 1.5 m/s current velocities showed up to a 14‐fold flood tide enhancement of mussel larvae and bysally drifting juveniles. Thus certain Maine estuaries may act as larval traps, providing areas of concentrated settlement and seed abundance. Primary setting normally begins with a large initial pulse in June followed by one or more secondary pulses throughout the summer. Secondary settlement (reattachment of bysally drifting juveniles) occurs at lower levels throughout the year, especially in late July and early August. Maximum attachment of larvae and juveniles occurs during periods of maximum current velocity. Extensive eelgrass beds at the mouths of some estuaries (i.e., Jordan River) may be the sites of extensive primary and secondary setting. Great Eastern Mussel Farms, the industry component, guided by these studies, is testing the deployment of live and shell mussel cultch to develop and optimize a new seed procurement system

Copepods of the genus Oithona from Cananéia region (Lat. 25º07'S, Long. 47º56' W)

Some ecological aspects of two congeneric species of Cyclopoid copepods, Oithona Ovalis and O. oligohalina have been studied for the first time in the estuarine region of Cananeia. The spatial distribution and seasonal variation of both species of Oithona are studied in relation to salinity, temperature and dissolved, oxygen. The results obtained are compared to previous work done in the area and to similar studies undertaken elsewhere.Alguns aspectos ecologicos de duas espécies congenéricas de copépodos ciclopoides, Oithona ovalis e O. oligohalina são estudados pela primeira vez na região estuarina de Cananéia. A distribuição espacial e variaçao sazonal destas especies sao estudadas em relaçao â salinidade, temperatura e oxigénio dissolvido. Os resultados obtidos sao comparados com trabalhos preliminares feitos nesta área e estudos similares em outras regiões. As principais conclusões obtidas são as seguintes: 1 - O. ovalis ocorre em uma faixa de salinidade de 12,67‰ a 27,16‰ e O. oligahalina em 3,45 a 16,48‰. 2 - A presença de duas espécies congenericas estreitamente relacionadas cuja distribuição se recobre parcialmente em uma estreita faixa de salinidade sugere que o género Oithona sofreu especiação dentro do estuário. 3 - A salinidade tem um papel importante na ocorrência e distribuição destas espécies desde que a temperatura nunca alcançou valores limitantes para estas espécies