Biomarkers in fish from dioxin-contaminated fjords

The Grenland fjords, southern Norway, have been heavily contaminated by dibenzo-p-dioxins and dibenzofurans (dioxins) over decades through inputs from a magnesium smelter. Despite radically decreased inputs since 1990, there are still high levels of dioxins in both biotic and abiotic components of the fjords. The aim of the study was to establish whether biomarkers' responses in three fish species, Atlantic cod (Gadus morhua L.), sea-trout (anadromous brown trout, Salmo trutta L.) and flounder (Platichthys flesus L.), could be used to discern the effects in the most contaminated ecosystem, Frierfjord, from the effects in the adjacent, less-contaminated ecosystem, Eidangerfjord. Biomarker responses clearly indicated that the three fish species were affected by dioxin exposure. Phase I responses in cod and trout could be used to differentiate exposure in the two fjord ecosystems. Phase II responses (glutathione S-transferase) in cod and trout similarly indicated a higher dioxin exposure in Frierfjord compared with Eidangerfjord. Results for glutathione S-transferase and glutathione reductase indicated different exposure levels in the two fjords, but also showed seasonal variability, and the results highlighted the need for baseline data for these biomarkers.     

Trophically transmitted parasites in wild Atlantic salmon post‐smolts from Norwegian fjords

The community structure of trophically transmitted intestinal helminths of Atlantic salmon Salmo salar post‐smolts was highly variable among four fjords in Norway. There were no severely pathogenic parasite species. Post‐smolts from the southernmost Trondheimsfjord had a higher diversity of freshwater parasite species compared to the three northern fjords (Tanafjord, Altafjord and Malangen). In contrast, the highest diversity and proportion of marine species was found in the three northern fjords. Post‐smolts were generally more infected with marine parasites in the outer rather than inner parts of all of the fjords. The prevalence of the acanthocephalan Echinorynchus gadi (range: 13–42%) and marine trematodes (range: 14–47%) was higher in post‐smolts in outer zones of the northern fjords than in fish from Trondheimsfjord (0 and 6%, respectively). The within‐fjord variability and north‐south geographical gradient in parasite infection patterns reflected differences in marine feeding of the post‐smolts on potential intermediate hosts such as amphipods ( E. gadi ) and fish larvae (trematodes), which were higher in the northern fjords (range: 27–28 and 67–85%, respectively) than in Trondheimsfjord (5 and 19%, respectively). High intensities of marine parasites suggest that some post‐smolts from northern fjords may have a prolonged fjord‐feeding compared to those from Trondheimsfjord. Parasites of both freshwater and marine origin appear to be suitable as bio‐indicators of feeding and migratory pattern of Atlantic salmon post‐smolts and preadults during their seaward migration.     

Biomarkers in fish from dioxin-contaminated fjords

Abstract

The Grenland fjords, southern Norway, have been heavily contaminated by dibenzo-p-dioxins and dibenzofurans (dioxins) over decades through inputs from a magnesium smelter. Despite radically decreased inputs since 1990, there are still high levels of dioxins in both biotic and abiotic components of the fjords. The aim of the study was to establish whether biomarkers’ responses in three fish species, Atlantic cod (Gadus morhua L.), sea-trout (anadromous brown trout, Salmo trutta L.) and flounder (Platichthys flesus L.), could be used to discern the effects in the most contaminated ecosystem, Frierfjord, from the effects in the adjacent, less-contaminated ecosystem, Eidangerfjord. Biomarker responses clearly indicated that the three fish species were affected by dioxin exposure. Phase I responses in cod and trout could be used to differentiate exposure in the two fjord ecosystems. Phase II responses (glutathione S-transferase) in cod and trout similarly indicated a higher dioxin exposure in Frierfjord compared with Eidangerfjord. Results for glutathione S-transferase and glutathione reductase indicated different exposure levels in the two fjords, but also showed seasonal variability, and the results highlighted the need for baseline data for these biomarkers.     

Disentangling structural genomic and behavioural barriers in a sea of connectivity

Genetic divergence among populations arises through natural selection or drift and is counteracted by connectivity and gene flow. In sympatric populations, isolating mechanisms are thus needed to limit the homogenizing effects of gene flow to allow for adaptation and speciation. Chromosomal inversions act as an important mechanism maintaining isolating barriers, yet their role in sympatric populations and divergence with gene flow is not entirely understood. Here, we revisit the question of whether inversions play a role in the divergence of connected populations of the marine fish Atlantic cod (Gadus morhua), by exploring a unique data set combining whole‐genome sequencing data and behavioural data obtained with acoustic telemetry. Within a confined fjord environment, we find three genetically differentiated Atlantic cod types belonging to the oceanic North Sea population, the western Baltic population and a local fjord‐type cod. Continuous behavioural tracking over 4 year revealed temporally stable sympatry of these types within the fjord. Despite overall weak genetic differentiation consistent with high levels of gene flow, we detected significant frequency shifts of three previously identified inversions, indicating an adaptive barrier to gene flow. In addition, behavioural data indicated that North Sea cod and individuals homozygous for the LG12 inversion had lower fitness in the fjord environment. However, North Sea and fjord‐type cod also occupy different depths, possibly contributing to prezygotic reproductive isolation and representing a behavioural barrier to gene flow. Our results provide the first insights into a complex interplay of genomic and behavioural isolating barriers in Atlantic cod and establish a new model system towards an understanding of the role of genomic structural variants in adaptation and diversification.     

Genome architecture enables local adaptation of Atlantic cod despite high connectivity

Adaptation to local conditions is a fundamental process in evolution; however, mechanisms maintaining local adaptation despite high gene flow are still poorly understood. Marine ecosystems provide a wide array of diverse habitats that frequently promote ecological adaptation even in species characterized by strong levels of gene flow. As one example, populations of the marine fish Atlantic cod (Gadus morhua) are highly connected due to immense dispersal capabilities but nevertheless show local adaptation in several key traits. By combining population genomic analyses based on 12K single nucleotide polymorphisms with larval dispersal patterns inferred using a biophysical ocean model, we show that Atlantic cod individuals residing in sheltered estuarine habitats of Scandinavian fjords mainly belong to offshore oceanic populations with considerable connectivity between these diverse ecosystems. Nevertheless, we also find evidence for discrete fjord populations that are genetically differentiated from offshore populations, indicative of local adaptation, the degree of which appears to be influenced by connectivity. Analyses of the genomic architecture reveal a significant overrepresentation of a large ~5 Mb chromosomal rearrangement in fjord cod, previously proposed to comprise genes critical for the survival at low salinities. This suggests that despite considerable connectivity with offshore populations, local adaptation to fjord environments may be enabled by suppression of recombination in the rearranged region. Our study provides new insights into the potential of local adaptation in high gene flow species within fine geographical scales and highlights the importance of genome architecture in analyses of ecological adaptation.     

Seasonal occurrence of sea lice Lepeophtheirus salmonis on sea trout in two north Norwegian fjords

Seasonal occurrence of the parasitic copepod Lepeophtheirus salmonis (sea lice) was studied from March to December 2001 in two large north Norwegian sill fjords without fish farming activity, the Ranafjord and the Balsfjord. Anadromous brown trout Salmo trutta (sea trout) in both fjords had a low infestation rate during all sampling periods, but followed a seasonal pattern. During early and late winter (November to December and March to April) and spring (May to June), the prevalence varied from 0 to 25% and the abundance was <0·5 sea lice. Adults dominated (92%) during this period, particularly gravid females. In both fjords, the highest prevalence was during September (80–81%, all stages represented). In Ranafjord, the abundance and mean intensity during this month was 6·8 and 8·6 sea lice, respectively, while in Balsfjord it was 3·6 and 4·5 sea lice, respectively. Fish were captured at temperatures down to 1° C and at full strength sea water which is supposed to cause osmoregulatory problems for the fish. This observation has implications for the understanding of high‐latitude sea trout behaviour and can also make the fish more vulnerable to heavy sea lice infestation during this period. It is suggested that winter running sea trout help to maintain a self replicating local population of sea lice within such fjord systems where other possible hosts ( e.g . farmed Atlantic salmon Salmo salar ) are not present during a whole year cycle.     

From the worm’s point of view. I: Environmental settings of benthic ecosystems in Arctic fjord (Hornsund,Spitsbergen)

As a consequence of ongoing climate warming, nearly all tidal glaciers in Arctic are retreating; hence, the seascape of glacial fjords is changing in many aspects. We took the example of Hornsund, the well-studied Svalbard fjord, with over 30 years of almost continuous observations of marine system. Recent data were collected during summer oceanographic surveys between 2001 and 2013 and compared with archival data from 1980s. As most of the phenomena connected with the warming happen at the sea surface (ice, wind, waves, surface currents, brackish water), we were interested, how the presumably stable, near-bottom waters in fjords behave, what are the environmental changes that are experienced directly by the worms living in the sediment. We have found that both the inner fjord basins (usually regarded as stable) and the outer fjord parts (exposed to the direct influence of shelf waters) has changed. Warming was documented in the inner basins, while cooling and warming episodes were recorded in the outer parts of the fjord. We demonstrate that following the increase melting and retreat of the glaciers, the area of shallows increased, salinity decreased and temperature increased—partly due to the advection of Atlantic waters from the shelf. Observed changes are in accordance with the model of arctic fjords evolution towards boreal ones associated with increased organic matter turnover. The observed changes are most likely typical for all cold water, glaciated fjords that are exposed to climate warming.     

Effects of salmon lice infection and salmon lice protection on fjord migrating Atlantic salmon and brown trout post-smolts

Effects of artificial salmon lice infection and pharmaceutical salmon lice prophylaxis on survival and rate of progression of Atlantic salmon (n = 72) and brown trout post-smolts (n = 72) during their fjord migration, were studied by telemetry. The infected groups were artificially exposed to infective salmon lice larvae in the laboratory immediately before release in the inner part of the fjord to simulate a naturally high infection pressure. Groups of infected Atlantic salmon (n = 20) and brown trout (n = 12) were also retained in the hatchery to control the infection intensity and lice development during the study period. Neither salmon lice infection nor pharmaceutical prophylaxis had any effects on survival and rate of progression of fjord migrating Atlantic salmon post-smolts compared to control fish. Atlantic salmon spent on average only 151.2 h (maximum 207.3 h) in passing the 80 km fjord system and had, thus, entered the ocean when the more pathogenic pre-adult and adult lice stages developed. The brown trout, in comparison to Atlantic salmon, remained to a larger extent than Atlantic salmon in the inner part of the fjord system. No effect of salmon lice infection, or protection, was found in brown trout during the first weeks of their fjord migration. Brown trout will, to a larger extent than Atlantic salmon, stay in the fjord areas when salmon lice infections reach the more pathogenic pre-adult and adult stages. In contrast to Atlantic salmon, they will thereby possess the practical capability of returning to freshwater when encountering severe salmon lice attacks.     

Geographical differences in marine feeding of Atlantic salmon post‐smolts in Norwegian fjords

Stomach content analyses were conducted on Atlantic salmon Salmo salar post‐smolt (average size, 119–154 mm fork length, L _F) caught in eight large Norwegian fjord systems along a north–south geographical axis during 1998–2001. In general, post‐smolts from southern Norway showed low feeding intensity in the fjords, whereas extensive feeding was observed in fjords in the northern and middle parts of Norway. The marine diet mainly included different crustaceans and in particular marine pelagic fish larvae (sand-eels Ammodytes spp., herring Clupea harengus and gadoids), but with a substantial spatial and annual variation in prey diversity and feeding intensity. Insects were most frequently taken in the estuary, although fishes often made a large contribution in mass. In contrast, fishes, and to some extent various crustaceans (particularly Hyperiidae, Gammaridae, Euphausiacea and Copepoda) dominated the diet in the middle and outer parts of the fjords, where post‐smolts also fed more extensively than in the inner part. The results indicate that extensive feeding immediately after sea entrance may be more common for post‐smolts in the northern and middle parts of Norway, than in the southern fjords. The observed differences in post‐smolt feeding may be due to spatial and temporal differences in prey availability within and between the different types of fjord systems, and this might influence post‐smolt growth and survival.     

Distinct or similar? Soft bottom polychaete diversity in Arctic and Antarctic glacial fjords

The main aim of this study was to compare the polychaete communities in two similar polar areas: an Arctic fjord, Hornsund (Svalbard) and an Antarctic fjord, Ezcurra Inlet (South Shetlands). This is the first attempt to compare Arctic and Antarctic diversity based on fully comparable datasets. Forty van Veen grab samples were collected in each fjord: twenty replicates were taken in each of two fjord areas characterized by a different level of glacial disturbance—in the inner (glacial bay) and outer (fjord mouth) region of both fjords, from depths of about 100 m in 2005 (Hornsund) and in 2007 (Ezcurra Inlet). In the glacial bays, species richness and diversity were significantly higher in Ezcurra Inlet than in Hornsund due to higher rate of glacial disturbance in the latter one. In the outer areas, species richness was similar in both fjords, although diversity values were higher in Ezcurra Inlet. Polychaete species richness in the habitats characterized by similar level of disturbance (outer areas of the fjords) was the same in both polar regions. At this small scale, where community drivers are very similar, the species richness seems to be independent from the local or regional species pool.     

Habitat use and early winter movements by juvenile Atlantic cod in a coastal area of Newfoundland

Acoustic telemetry was used to monitor the movements and landscape scale habitat use of age 2–3 year juvenile Atlantic cod Gadus morhua in Newman Sound, a coastal fjord of Newfoundland, during late autumn and early winter (24 October 1999 to 22 January 2000). Substratum, bathymetric relief and depth use were studied to determine if it differed from the pattern expected given an absence of selectivity (habitat use proportional to habitat availability). Prior to winter migrations, most Atlantic cod maintained small home ranges (0·5–33·4 ha, median = 2·1 ha) although a few individuals moved more widely. No relationship between total length (L_T) and home range size was detected. In Inner Newman Sound, Atlantic cod occupied depths of 10–29 m more than expected given availability, while depths of 0–9 and 40–59 m were underutilized. No significant relationship between depth and L_T was detected. Areas of medium (5–10%) or high (>10%) bathymetric relief and boulder or kelp habitats were used significantly more than expected given the availability of these habitats. Sand and eelgrass substrata were underutilized given availability, although many Atlantic cod used sandy‐bottomed areas to some degree. Flexibility in habitat use by the individuals that were studied suggested reduced predation risk relative to younger conspecifics. Winter migrations to deeper water beyond Newman Sound began in mid‐November, coinciding with the disappearance of the thermocline, and continued until 27 December. Approximately 30% of monitored individuals did not migrate and maintained their home ranges into the winter season. No significant differences in L_T between migrating and resident groups were detected, however, the condition of migrating fish was significantly higher than in resident fish. This finding supports the theory that feeding history plays a role in the decision to undertake migration.     

Sea surface temperature dictates movement and habitat connectivity of Atlantic cod in a coastal fjord system

While movements of organisms have been studied across a myriad of environments, information is often lacking regarding spatio‐seasonal patterning in complex temperate coastal systems. Highly mobile fish form an integral part of marine food webs providing linkages within and among habitats, between patches of habitats, and at different life stages. We investigated how movement, activity, and connectivity patterns of Atlantic cod (Gadus morhua) are influenced by dynamic environmental conditions. Movement patterns of 39 juvenile and subadult Atlantic cod were assessed in two coastal sites in the Swedish Skagerrak for 5 months. We used passive acoustic telemetry and network analysis to assess seasonal and spatial movement patterns of cod and their relationships to different environmental factors, using statistical correlations, analysis of recurrent spatial motifs, and generalized linear mixed models. Temperature, in combination with physical barriers, precludes significant connectivity (complex motifs) within the system. Sea surface temperature had a strong influence on connectivity (node strength, degree, and motif frequency), where changes from warmer summer waters to colder winter waters significantly reduced movement activity of fish. As the seasons changed, movement of fish gradually decreased from large‐scale (km) linkages in the summer to more localized movement patterns in the winter (limited to 100s m). Certain localized areas, however, were identified as important for connectivity throughout the whole study period, likely due to these multiple‐habitat areas fulfilling functions required for foraging and shelter. This study provides new knowledge regarding inshore movement dynamics of juvenile and subadult Atlantic cod that use complex, coastal fjord systems. The findings show that connectivity, seasonal patterns in particular, should be carefully considered when selecting conservation areas to promote marine stewardship.     

Is the poleward expansion by Atlantic cod and haddock threatening native polar cod, <Emphasis Type="Italic">Boreogadus saida</Emphasis>?

During a recent period of increased influx of warm Atlantic water to the western coast of Svalbard, we have observed a northward expansion of boreal Atlantic cod (Gadus morhua) and haddock (Melanogrammus aeglefinus) into areas dominated by the native polar cod (Boreogadus saida). To determine the potential impact of new ecological interactions, we studied the diet of co-occurring juvenile gadoids in fjords, open water, and sea ice around Svalbard. We also reviewed the available literature on polar cod feeding in different habitats across the Arctic to determine whether region, habitat, or fish size may influence diet. Feeding by polar cod in the pelagic zone was size dependent, with small fish primarily consuming Calanus spp. and smaller copepods, with an increasing ration of Themisto spp. at larger sizes. In benthic habitats, diets were more varied and included considerably more unidentified material and sediment. Less than 40% dietary overlap was detected among the three species when they were found together. Stable isotope analyses indicated these patterns were representative of longer-term assimilation. The low interspecific dietary overlap suggests little direct competition. Future increases in abundance and the high predation potential of the boreal taxa, however, may impact the persistence of polar cod on some Arctic shelves.     

Migration of hatchery‐reared Atlantic salmon and wild anadromous brown trout post‐smolts in a Norwegian fjord system

Hatchery‐reared Atlantic salmon Salmo salar ( n  = 25) and wild anadromous brown trout (sea trout) Salmo trutta ( n  = 15) smolts were tagged with coded acoustic transmitters and released at the mouth of the River Eira on the west coast of Norway. Data logging receivers recorded the fish during their outward migration at 9, 32, 48 and 77 km from the release site. Seventeen Atlantic salmon (68%) and eight sea trout (53%) were recorded after release. Mean migratory speeds between different receiver sites ranged from 0·49 to 1·82 body lengths (total length) per second (bl s⁻¹) for Atlantic salmon and 0·11–2·60 bl s⁻¹ for sea trout. Atlantic salmon were recorded 9, 48 and 77 km from the river mouth on average 28, 65 and 83 h after release, respectively. Sea trout were recorded 9 km from the release site 438 h after release. Only four (23%) sea trout were detected in the outer part of the fjord system, while the rest of the fish seemed to stay in the inner fjord system. The Atlantic salmon stayed for a longer time in the inner part than in the outer parts of the fjord system, but distinct from sea trout, migrated through the whole fjord system into the ocean.     

Migration and capture of pink salmon, Oncorhynchus gorbuscha Walbaum in Finnmark, North Norway

Pink salmon transplanted to the north Atlantic coast from the Soviet Union reached a peak in 1973, both in the Soviet Union and in Finnmark. Pink salmon catch statistics were compiled in 1977 for the inshore coastal and fjord areas of Finnmark from the atlantic salmon fisheries conducted locally and outside the coastal limits of Finnmark. The survey indicated a total sea catch of 12 800 specimens or 18 450 kg in Finnmark in 1977. The pink salmon reached the coast in the western regions of Finnmark during the first half of July, after which the main migration continued eastwards along the coast. The migrations into the western fjords were few, with half the total inshore catch captured in the most eastern fjord, Varangerfjord.     

Distribution of diatom surface sediment assemblages within Effingham Inlet, a temperate fjord on the west coast of Vancouver Island (Canada)

Twenty-nine surface sediment samples from Effingham Inlet, a small fjord on the west coast of Vancouver Island, British Columbia, were analyzed for diatoms. This fjord has been selected for paleoceanographic investigation due to the presence of laminated sediments resulting from the dysoxic to anoxic bottom water conditions in the inner and outer basins of the inlet. Distributional patterns of the diatom microflora reflected proximity to littoral regions, phytoplankton production, and marine influence from outside the fjord. Principal components and cluster analyses of the microflora established four diatom assemblages with a clear separation between the inner and outer basin diatom floras. Inner basin stations were characterized by elevated absolute abundance with assemblages dominated by spring–early summer bloom taxa including Skeletonema costatum, Thalassiosira nordenskioeldii, and Thalassiosira pacifica. Chaetoceros spp. resting spores were abundant throughout Effingham Inlet, with the exception of the stations closest to the fjord head. Stations located in the outer basin and towards the fjord mouth had relatively lower absolute abundance yet showed a higher relative and absolute abundance of Thalassionema nitzschioides, Rhizosolenia setigera, Coscinodiscus radiatus, Ditylum brightwellii, Odontella longicruris, and Paralia sulcata in relation to the inner basin. Many of these latter taxa are often associated with late summer and autumn conditions in fjords along coastal British Columbia. Oceanographic data for Effingham Inlet suggest that increased offshore penetration is more likely to occur from summer to early fall, with a more restricted offshore influence in the inner basin. Diatom surface sediment assemblages in Effingham Inlet appear to reflect incursions of offshore waters into the fjord. Absolute abundance estimates and the preservation of lightly silicified taxa suggest excellent preservation of fossil material in the sediments of the predominantly anoxic inner basin. Preservation in the outer basin is reduced, reflecting more frequent recharge by oxygenated waters spilling over the outer sill into the basin. Our findings suggest the inner basin should be an optimal site for reconstruction of diatom production, with records from the outer basin providing more consistent information about offshore influence and coastal upwelling conditions over the Holocene. Estimates of diatom abundance within the inner basin sediment may serve as a good proxy of production, although proxy tracers of bottom water conditions and sedimentological analyses must be coupled to the diatom record to ensure depositional conditions were not influencing valve preservation or abundance. Our results suggest that fjords can serve as good environments for paleoceanographic reconstructions of both inshore and offshore conditions although careful site selection and understanding of processes affecting the microfossil record are essential.     

Antimicrobial activity in serum of Atlantic cod Gadus morhua L.: comparison between cultured and wild fish

The present investigation determined the antibacterial activities in the sera of both cultured and wild Atlantic cod Gadus morhua . Serum samples from both groups of fish were quantified for total protein, and their effects against fish pathogens Listonella anguillarum , Aeromonas salmonicida and Yersinia ruckeri were determined using co-incubation assay. Total serum protein concentrations were not significantly different between farmed and wild Atlantic cod. Sera of cultured Atlantic cod significantly decreased growth of L. anguillarum by at least two-log₁₀ reductions in bacterial count, while those of the wild Atlantic cod were able to inhibit the growth of all three fish bacterial pathogens. The present study showed that sera from wild fish possess broader antibacterial activities than cultured Atlantic cod and that these could provide an explanation for the differences regarding their immunity to bacterial infections as well as their health status.     

Genetic divergence at the synaptophysin (Syp I) locus among Norwegian coastal and north-east Arctic populations of Atlantic cod

Several nuclear RFLP loci have been discovered recently that exhibit extensive allele frequency variation among Norwegian coastal and north-east Arctic populations of Atlantic cod Gadus morhua. One of these polymorphisms was detected by hybridizing an anonymous cDNA clone (GM798) against genomic DNA digested with the restriction enzyme DraI. This cDNA clone has now been sequenced and identified as synaptophysin (Syp I), an integral synaptic vesicle membrane protein. Primers were constructed that amplify an intron of the Syp I gene that is polymorphic for the DraI site, thus making it possible to use a PCR-based assay to score the polymorphism. A total of 965 individuals sampled from the Barents Sea, coastal areas and fjords in northern Norway have been analysed for this polymorphism. The results confirm that highly significant differences exist between NE Arctic and coastal cod at the Syp I locus. A cluster analysis revealed a deep split between coastal and Arctic populations and hierarchical F-statistics indicated that about 40% of the total variation was attributable to differences between Arctic and coastal groups. The temporal stability of allele frequencies was assessed by comparing Syp I allele frequencies among samples of juveniles (0 group) captured at specific locations in fjords in consecutive years and among samples of adults and juveniles collected from the same fjord. Samples of juveniles collected in 1994 and 1995 in Malangen were genetically indistinguishable whereas juveniles sampled from Dønnesfjord and Ullsfjorden over the same 2-year period exhibited significant differences. Adults and 0-group individuals collected from the same fjord were found to be genetically indistinguishable in Malangen, but not in Balsfjorden. In addition to detecting large differences among Arctic and coastal groups, the Syp I locus suggests that genetic heterogeneity exists among resident populations of cod in different fjords and that gene flow among populations throughout northern Norway may be considerably lower than previously believed.     

Movements and dispersal of farmed Atlantic salmon following a simulated-escape event

One of the major challenges for understanding the ecological impact of escaped farmed Atlantic salmon (Salmo salar L.) is predicting their dispersal patterns after an escape event. Here, we quantify the behaviour of escaped farmed salmon using a simulated-escape experiment within a Norwegian fjord system. Thirty-seven individuals were tagged with acoustic transmitters and their spatial distribution, horizontal movements and diving behaviour was monitored throughout the fjord and accompanying rivers using 29 acoustic receivers. A rapid movement away from the release site occurred. There was no movement into the rivers feeding the fjord and there was no preference for residence at the fish farms: nearly a third of the individuals had a final detection in the outer part of the fjord and no detections occurred from approximately 2 months after release. As it is unlikely that all fish died or remained undetected within the study area it is reasonable to assume that a substantial proportion of the fish moved out of the fjord system. If a recapture program is not implemented immediately after an escape event, we recommend spreading potential recapture efforts over a relatively large area.