Plankton studies in Buzzards Bay, Massachusetts, USA. V. ichthyoplankton, 1987 to 1993

Abstract

Monthly sampling for ichthyoplankton was conducted at 8 stations in Buzzards Bay, Massachusetts, from October 1987 to September 1993 using a 48 cm diameter plankton net with 0.102 mm mesh. From October 1992 to September 1993, an additional 75 cm diameter net with 0.202 mm mesh was also towed to compare mesh selectivity. Stations included two with heavy anthropogenic impact, the urbanized inner harbor of New Bedford, Massachusetts, and over New Bedford's offshore sewage outfall, as well as other nearshore shallow and offshore deep stations in comparatively pristine areas of the bay. Fish larvae from 32 genera were identified. Fish eggs were counted but not identified. There was a pronounced summer peak in larval abundance dominated by cunner Tautogolabrus adspersus, anchovy Anchoa sp. and tautog Tautoga onitis. A smaller winter/early spring peak was dominated by sand lance Ammodytes sp. This pattern was evident for all 6 years of the study. The assemblage of fish larvae found in Buzzards Bay differed from that in Cape Cod Bay, lending support to the concept of Cape Cod as a faunal boundary. The 2 differently sized nets used during the last year of the study did not catch significantly different numbers of fish larvae per m3, but length frequency distributions of 4 abundant species of larvae révealed that the smaller mesh net caught significantly smaller Anchoa sp. The larger mesh net collected significantly more species of fish larvae. A comparison of annual mean catches of 4 species did not reveal significant changes in abundance over 6 yr.