Effects of shellfish farming on the benthic environment

Abstract

The benthic environment under and near three shellfish farms in Tasmania, Australia, which had had a relatively high level of production over many years was investigated. Benthic samples were collected along transects which ran across the farms, generally from 100 m upstream to 100 m downstream. Sediment deposition, redox values, sediment sulphide concentrations, organic carbon content and water turbidity levels near the bottom were significantly different between the farms but not between sites outside the farm, at the boundary and sites within the farm. Video recordings at one farm showed dense coverage of fine filamentous algae and patchy bacterial mats directly under some longlines and this algae is thought to have fallen off the mussel longlines. At another farm dense beds of seagrass were observed in the videos both under trays of oysters and outside the farm. The benthic infauna did not show clear signs of organic enrichment, and neither univariate nor multivariate measures of benthic infauna were significantly different between sites inside and outside the farm, although they were different between farms.It was concluded from these results that shellfish farming is having little impact, and much less than salmon farming, on the benthic environment in Tasmania. Thus extensive monitoring of shellfish farms would appear to be not necessary. D

Influence of filtering and biodeposition by the cultured scallop Chlamys farreri on benthic-pelagic coupling in a eutrophic bay in China

“…7). This is in agreement with other studies (Grant et al 1995, Chamberlain et al 2001, Crawford et al 2003. Although a shift toward anaerobic metabolism at bivalve culture sites may exist, the impact of the build-up of discarded cultured organisms, and fouling algae or ascidians beneath longline culture sites, is more noticeable than any impacts from bivalve biodeposition (Grant et al 1995, Zhou 2000, Stenton-Dozey et al 2001.…”

Effects of intensive scallop mariculture on macrobenthic assemblages in Sishili Bay, the northern Yellow Sea of China

“…Minimal effects were observed in both areas, most likely because of the relatively low TOC concentration. In contrast to the study described by Crawford et al (2003), this study area has suffered from high culture density and should be able to produce enough organic matter to negatively affect the macrobenthos; therefore, the strength of water flow is likely to be the key factor responsible for the negligible impact of scallop culture on this macrobenthic community and is inversely correlated with benthic impacts (Borja et al, 2009). The highest tidal flow was 28.5-30 cm s -1 during the ebb and flood tides, and water flow was typically 14.8 cm s -1 in the summer (Zhang & Dong, 1990;Yanlin Cui, personal communication), disregarding the influence of the wind.…”

Small-scale spatial variability of food partitioning between cultivated oysters and associated suspension-feeding species, as revealed by stable isotopes

“…In many estuarine and coastal ecosystems, commercial farming of shellfish is an important industry (Crawford et al 2003). The carrying capacity of shellfish ecosystems has been investigated with models that assumed these species to feed in the same trophic niche and compete for the same food resources (see review by Prins et al 1998).…”