Vicinity Of Cages Research Articles

Benthic metabolism and nitrogen transformations affected by fish cage farming in the tropical Nha Phu estuary (Vietnam)

Effects of organic-waste loading from fish farming on benthic metabolism and nitrogen (N) cycling were studied in the tropical Nha Phu Estuary, Vietnam. The loading of fish excreta and feed waste enhanced benthic oxygen (O2) uptake two times and total carbon dioxide (TCO2) release three times, compared with the reference station. NH4+ was the major form of released N, comprising 94–100% of dissolved inorganic N (DIN) flux below and near fish cages. Only 3% and 1% of organic carbon (OC) and organic N (ON) deposited from the fish farm was degraded in the sediment, whereas the rest was dispersed to adjacent areas via tidal currents or buried into the sediment. Coupled nitrification–denitrification were almost 0 under fish cages but increased at distances greater than 10 m from fish cages. Consequently, biologically available N was not removed permanently near fish cages as the excess N deposited under cages were mineralised and released as DIN. The nutrient efflux could therefore potentially be a source for pelagic primary production in the vicinity of cages. However, the water currents and low water residence time may have distributed and diluted the nutrient effect of cages to the entire estuary and the adjacent ocean.

Physiological responses of the seagrass Posidonia oceanica as indicators of fish farm impact

The development of aquaculture along the Mediterranean coastline degrades the marine environment, in particular Posidonia oceanica meadows, which, in extreme cases, show high mortality. Here we studied the effects of organic matter and nutrient input from the effluents of three fish farms, located along the Mediterranean coast, on P. oceanica physiology. For this purpose, we measured physiological variables such as total nitrogen (N) content, free amino acid (FAA) concentration and composition, N stable isotope ratio ( δ 15N), total phosphorus (P) content and total non-structural carbohydrate (TNC) content in plant tissues and epiphytes affected by organic discharges (highly impacted stations: HI, and less impacted stations: LI) and compared these results with those obtained in references sites (control stations: C). For all the descriptors analyzed in P. oceanica epiphytes, the values recorded in the vicinity of cages were, in general, much higher than those in C. Leaves did not respond consistently in any case. Total N content and δ 15N in epiphytes together with the total P content in rhizomes and epiphytes were the physiological descriptors that showed the most consistent responses to fish farm effluents. On the basis of these observations, we conclude that fish farm activities strongly affect the physiological parameters of nearby P. oceanica meadows. We propose that changes in these physiological parameters may be useful indicators of marine environmental degradation in studies that monitor the effects of fish farming.

Impact of fish farms on maerl beds in strongly tidal areas

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 326:1-9 (2006) - doi:10.3354/meps326001 Impact of fish farms on maerl beds in strongly tidal areas Jason Hall-Spencer1,*, Nicola White2, Ewan Gillespie3, Katie Gillham4, Andy Foggo1 1Plymouth Marine Institute, University of Plymouth, Drake Circus, Plymouth PL4 8AA, UK 2Haskoning UL Ltd, Elizabeth House, Emperor Way, Exeter EX1 3QS, UK 3Scottish Environment Protection Agency, Dingwall IV7 9X8, UK 4Scottish Natural Heritage, Westercraigs, Inverness IV3 8NW, UK *Email: jhall-spencer@plymouth.ac.uk ABSTRACT: In Scotland, Atlantic salmon Salmo salar cages are being moved out of areas with slow water movements, to disperse wastes and reduce impacts on benthic communities. This first study of the effects of fish farms on maerl beds (red algal coralline gravels of high conservation importance) demonstrated major impacts on the benthos, even in strongly tidal areas. SCUBA surveys of 3 fish farms located over maerl revealed a build-up of waste organic matter and 10 to 100-fold higher abundances of scavenging fauna (e.g. Necora puber, Pagurus bernhardus) than on 6 reference maerl beds. Visible waste was noted up to 100 m from cage edges, and all 3 farms caused significant reductions in live maerl cover, upon which this habitat depends. Near-cage infaunal samples showed significant reductions in biodiversity, with small Crustacea (ostracods, isopods, tanaids and cumaceans) being particularly impoverished in the vicinity of cages, and significant increases in the abundance of species tolerant of organic enrichment (e.g. Capitella spp. complex, Ophryotrocha hartmanni). Relocation of fish farms to areas with strong currents is unlikely to prevent detrimental effects to the structure and organisation of the benthos, and ‘fallowing’ (whereby sites are left unstocked for a period of time to allow benthic recovery) is inadvisable where slow-growing biogenic habitats such as maerl are concerned, as this may expand the area impacted. KEY WORDS: Salmon farming · Maerl · Organic enrichment · Benthos · Scotland Full text in pdf format NextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 326. Online publication date: November 17, 2006 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2006 Inter-Research.

Effects of organic matter input from a fish farming facility on a Posidonia oceanica meadow

In the Mediterranean, the development of aquaculture along the coasts appears as a source of disturbance to the littoral ecosystems, and in particular to Posidonia oceanica seagrass meadows. Although the impact of fish farms in Northern Europe has been studied over the last few years, the data are more scarce in the Mediterranean. Thus, a number of physico-chemical and biological parameters have been examined here in order to evaluate the impact of a fish farm in a littoral bay of Corsica. The following values that were recorded in the vicinity of the fish farm are much higher than those at the reference station: organic content of the sediment (24–21 versus 2%), nitrogen concentrations (ammonium: 19.5–8.4 versus 1.8 μM) and phosphorous levels in the pore water (orthophosphates: 5.2–1.3 versus 1.7 μM). The seagrass meadow vitality also seems to be affected in the vicinity of cages, with densities that drop from 466 (reference station) to 108 shoots m −2 (20 m from cages). Total primary production also varies from 1070.6 to 87.9 g m −2 year −1. The main impact factors seem to be the input of organic matter originating from the cages and the high epiphyte biomass caused by the nutrient enrichment. The high level of organic matter and the presence of mud seem to alter the physico-chemical characteristics of the bottom sediment; moreover, the plant/epiphyte competition seems to lead to a leaf fragility and, more importantly, to a decrease in available light.

Detection of Pneumocystis carinii DNA by filtration of air.

The high incidence of pneumonia caused by Pneumocystis carinii in immunosuppressed patients makes it the most important parasite in non-tropical geographical regions. It has recently been shown to be a fungus, but several aspects of this organism are still poorly understood. A major question of clinical relevance is the nature of transmission and, thereby, the related problem of prevention. The mode of P. carinii transmission is thought to be air, but this is based on circumstantial evidence, the transmissive stage has not been identified. We attempted to capture P. carinii by filtration of air in the vicinity of cages containing P. carinii infected Wistar rats. Using nested polymerase chain reaction amplification of the thymidylate synthase gene to demonstrate P. carinii we were able to demonstrate P. carinii DNA on such filters. This strongly supports the suggested mechanism of transmission of Pneumocystis by means of airborne spores and suggests an approach to their isolation and characterization.

Rearing of coregonid fishes (Coregonidae) in illuminated lake cages: II. Environmental conditions during fish rearing

Observations of changes taking place in the environmental conditions during the rearing of coregonid fish ( Coregonus lavaretus L. and Coregonus peled Gmel.) in illuminated lake cages revealed that physical factors (water temperature, oxygen, transperency) were similar in the vicinity of cages and in other parts of the lake. The abundance of zooplankton near the cages increased at night 1.4-fold, in relation to the daytime value, because organisms were attracted by the light. Relatively high amounts of food for fishes kept in the cages occurred only during about 4 months of the year. The numbers of rotifers around cages was 1.2 times higher than in the cages, whereas those of Copepods and Cladocera were 1.4-fold higher. Along with the plankton, several fish species gathered around illuminated cages: viz. bleak ( Alburnus alburnus L.), perch ( Perca fluviatilis L.), roach ( Rutilus rutilus L.) and other small fishes. They fed in the same way as the fishes in the cages and thus constituted a factor limiting plankton numbers in cages.