Applicability of Perinereis aibuhitensis Grube for Fish Waste Removal from Fish Cages in Sanggou Bay,P.R.China

The present study investigated the applicability of integrated polychaete-fish culture for fish waste removal to offset negative impact induced by organic benthic enrichment.A field study demonstrated that deposition rate was significantly higher underneath the fish farm than that in control area.The material settling under the farm was characterized by a high amount of fish feces(45%) and uneaten feed(27%).Both feeding rate(FR) and apparent digestibility rate(ADR) increased with decreasing body weight,as was indicated by significantly a higher rate observed for the groups containing smaller individuals in a lab study.The nutrient in fresh deposited material(De) was higher than that in sediments collected under the farm(Se),resulting in lower feces production but higher apparent digestibility rate for the De group as feeding rate was similar.Consequently,higher nutrient removal efficiency was observed in the De group.A mass balance approach indicated that approximately 400–500 individuals m^(-2) is required for removing all waste materials deposited underneath the fish farm,whereas abundance can be lower(about 300–350 individuals m^(-2)) when only the fish waste needs to be removed.The results showed that a significant amount of waste had been accumulated in the fish cages in Sanggou Bay.The integration of fish with P.aibuhitensis seems promising for preventing organic pollution in the sediment and therefore is an effective strategy for mitigating negative effect of fish farms.Thus such integration can become a new IMTA(integrated multi-trophic aquaculture) model in Sanggou Bay.

Photo-Identification Methods Reveal Seasonal and Long-Term Site-Fidelity of Risso’s Dolphins (<i>Grampus griseus</i>) in Shallow Waters (Cardigan Bay, Wales)

A photo-identification study on Risso’s dolphins was carried out off BardseyIslandinWales(July to September, 1997-2007). Their local abundance was estimated using two different analytical techniques: (1) mark-recapture of well-marked dolphins using a ‘closed-population’ model;and (2) a census technique based on the total number of identified individual dolphins sighted over the study period. The mark-recapture estimates of 121 (left sides;64 - 178 95% CI;CV 0.24) and 145 dolphins (right sides;78 - 213 95% CI;CV 0.24) closely matched the census technique estimates (population size of 90 - 151). It was found that the dolphins showed a degree of long-term and seasonal site-fidelity. A first long-distance match was made for Risso’s dolphins (319 km) betweenBardseyIslandandCornwall, confirming they can be wide-ranging animals. This study demonstrates that the combination of systematic and opportunistic photo-ID studies has complementary value as a population assessment tool in generating the first local abundance estimate for Risso’s dolphins inUKwaters. From the conservation perspective, these studies confirm the regular presence of Risso’s dolphins in these waters and the presence of calves shows breeding.BardseyIslandmay be part of a network of localities that are important habitats to this species where it may take advantage of prey abundance in shallow waters. As such, results of this study may provide assistance to include the Risso’s dolphin in future regional conservation strategies including the envisaged marine protected areas.