Coastal aquaculture is a globally expanding enterprise. Currently, 1200 salmon farms operate in coastal Norway, yet their capacity to aggregate and subsequently modify wild fish distributions is poorly known. Aggregations of wild fish at 9 farms and 9 control locations were counted on 3 separate days in June to August 2007. On each sampling occasion, 6 counts were made at 5 distinct depth-strata at each farm and control location. Wild fish were 1 to 3 orders of magnitude more abundant at farms than at control sites, depending on the location. Gadoid fish (Pollachius virens, Gadus morhua and Melanogrammus aeglefinus) dominated farm-associated assemblages and were present across a wide range of sizes, from juveniles to large adults. Estimated total farmaggregated wild fish biomass averaged 10.2 metric tonnes (t) per farm across the 9 farms (range: 600 kg to 41.6 t). Applied across the geographical range of Norway's 1200 salmon farms, our estimates indicate that salmon farms attract and aggregate over 12 000 t of wild fish into a total of just 750 ha of coastal waters on any given day in summer. Possible consequences of these persistent, substantial aggregations of wild fishes at farms include a heightened potential for the transfer of pathogens from salmon farms to wild fish and among adjacent salmon farms, and altered availability of wild fish to fisheries. Restrictions on fishing in the immediate surrounds of salmon farms may avoid farms acting as ecological traps, particularly for species with depressed populations such as G. morhua, which are highly attracted to farms.

In Sweden, snu (locally known as snus), was introduced since the year 1637. Presently, Sweden has the highest per capita consumption and sale ®gures of snu in the world, and the habit is becoming increasingly popular. Snus is manufactured into a dry form used in the nasal cavity and a moist form used in the oral cavity. Snus manufactured for oral use is a moist ground tobacco of Dark Kentucky or Virginia species mixed with an aqueous solution of water and other blending ingredients. This form of snu is found in two types: (1) loose and (2) portion-bag-packed. These are the most widely used. The loose moist form (1±2 g a quid) is the most popular type consumed by 73% of the males, followed by the portion-bag-packed form (0.5±1 g a quid), consumed by 13% of the males, while 14% of the males are mixed users. The majority of snus users place the quid in the vestibular area of the upper lip, and the prevalence among persons 15 years of age or older is 15.9% among males and 0.2% among females. The pH of snus has declined from a previous range of 8±9 to a range of 7.8±8.5, moisture content ranges 35±60% and nicotine content is in the order of 5±11 mg/g dry wt tobacco-speci®c N-nitrosamines (TSNAs) in micrograms (N H -nitrosonornicotine: NNN 5±9; 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone: NNK 1±2; N H -nitrosoanatabine: NAT 2±5). In the Sudan, snu, locally known as toombak, was introduced approximately 400 years ago. It is always processed into a loose moist form, and its use is widespread in the country. Tobacco used for manufacture of toombak is of the species Nicotiana rustica, and the fermented ground powder is mixed with an aqueous solution of sodium bicarbonate. The resultant product is moist, with a strong aroma, highly addictive and its use is widespread particularly among males. Its pH range is 8±11, moisture content ranges 6±60% and nicotine content is from 8 to 102 mg/g dry wt, and TSNAs contents in micrograms (NNN 420±1 550; NNK 620±7 870; NAT 20±290). Snus and toombak dippers develop a clinically and histologically characteristic lesion at the site of dipping. Probably due to control of the TSNAs in snus, this type of snu is associated with a lower risk of cancer of the oral cavity (relative risk: RR 5±6-fold), whereas the risk for cancer of the oral cavity among toombak users was high (RR 7.3±73.0-fold). In conclusion, the two snu products signi®cantly dier in many aspects. Most notable dierences are tobacco species, fermentation and ageing, nicotine and TSNAs content, pH, expression of the p53 tumour supressor gene, and keratin types 13, 14, and 19. It was, therefore, the object of the present study to highlight the oral health hazards of toombak, and to compare it with snus regarding the aforementioned dierences. #

In Norway, 29 fjords and 52 rivers have been designated for protection in order to prevent the infection of important populations of wild salmonids with salmon lice of farm origin. We evaluated the effect of this protection on the lice infection pressure for wild salmonids based on lice counts performed on wild-caught sea trout and Arctic charr inside onethird of these protected fjords (known as 'National Salmon Fjords'). Results indicate that these areas may provide a certain extent of protection against lice of farm origin, but their configuration will play a key role in their success. When the size and shape of a protected area are such that fish farms are kept at a minimum distance (calculated here as at least 30 km, but this distance is likely site-dependent), wild fish seem unaffected by the direct lice infection pressure imposed by fish farms. In contrast, the effects of small protected fjords were strongly dependent on the production pattern of the aquaculture industry in the surrounding area, and we found a clear correlation between lice levels on wild salmonids and lice production in nearby salmon farms. To establish more precise management practices, both in National Sal mon Fjords and other fjord systems along the Norwegian coast, the development and validation of accurate distribution and abundance models for the dispersion of planktonic lice larvae is needed; this could also be the basis for an area management system based on 'maximum sustainable lice loads' or 'lice quotas.'

Commercial farming of Atlantic cod (Gadus morhua L.) is now being developed in several countries. The ecological consequences of cod culture are poorly understood, but recent research suggests that Atlantic cod are more prone to escape from net pens than Atlantic salmon. Here, we describe the movements and the spatiotemporal distribution of farmed cod after escape relative to wild cod, both during and outside the natural spawning season. The experimental design included simulating escape incidents of farmed cod tagged with acoustic transmitters and using an array of automatic listening stations to monitor their dispersal and distribution. For comparison, local wild cod were monitored using the same array of receivers. The farmed cod dispersed rapidly after a simulated escape, they randomly distributed over large areas and their distribution overlapped with local wild cod. Moreover, escaped farmed fish were found at local cod spawning areas during the spawning season. The study also indicated that the recapture rate of escaped farmed cod was high compared with that of escaped farmed salmon. Thus, while our results showed that there is a considerable potential for ecosystem effects caused by escaped farmed cod, mitigating actions such as an efficient recapture fishery for escapees may be possible.

BackgroundEcological traps form when artificial structures are added to natural habitats and induce mismatches between habitat preferences and fitness consequences. Their existence in terrestrial systems has been documented, yet little evidence suggests they occur in marine environments. Coastal fish farms are widespread artificial structures in coastal ecosystems and are highly attractive to wild fish.Methodology/Principal FindingsTo investigate if coastal salmon farms act as ecological traps for wild Atlantic cod (Gadus morhua) and saithe (Pollachius virens), we compared proxy measures of fitness between farm-associated fish and control fish caught distant from farms in nine locations throughout coastal Norway, the largest coastal fish farming industry in the world. Farms modified wild fish diets in both quality and quantity, thereby providing farm-associated wild fish with a strong trophic subsidy. This translated to greater somatic (saithe: 1.06–1.12 times; cod: 1.06–1.11 times) and liver condition indices (saithe: 1.4–1.8 times; cod: 2.0–2.8 times) than control fish caught distant from farms. Parasite loads of farm-associated wild fish were modified from control fish, with increased external and decreased internal parasites, however the strong effect of the trophic subsidy overrode any effects of altered loads upon condition.Conclusions and SignificanceProxy measures of fitness provided no evidence that salmon farms function as ecological traps for wild fish. We suggest fish farms may act as population sources for wild fish, provided they are protected from fishing while resident at farms to allow their increased condition to manifest as greater reproductive output.