Population Ecology and Epidemiology of Sea Lice in Canadian Waters

Sea lice are found on farmed and wild fish on both the west coast and east coast of Canada. The predominant species on both coasts is referred to as Lepeophtheirus salmonis but indications are that the two groups are genetically different. Caligus species are also found on both coasts, these too are different species: Caligus clemensi and C. elongatus, respectively. There has been extensive work on sea lice on both wild and farmed fish over the last decade. Research indicates that L. salmonis, commonly referred to as the salmon louse; may have a broader host range than commonly thought, infecting species such as the three-spine stickleback. The role of farmed salmon, particularly farmed Atlantic Salmon, as potential reservoirs of L. salmonis is accepted. What is still debated is the effect of sea lice infections on wild salmon populations, and whether the establishment of farm level treatment thresholds is the most appropriate method to manage the situation. There is indication that various Pacific salmon species have different tolerances to both L. salmonis and C. clemensi and the role of other non-salmon species in the ecology and epidemiology of sea lice still needs to be better researched. Published work on sea lice on farmed salmon on the East Coast is more limited; research on wild Atlantic Salmon even more so. This Research Document was presented and reviewed as part of the Canadian Science Advisory Secretariat (CSAS) National peer-review meeting, Sea Lice Monitoring and Non-Chemical Measures, held in Ottawa, Ontario, September 25-27, 2012. The objective of this peer-review meeting was to assess the state of knowledge and provide scientific advice on sea lice management measures, monitoring and interactions between cultured and wild fish

Sea lice on wild juvenile Pacific salmon and farmed Atlantic salmon in the northernmost salmon farming region of British Columbia

The Kitasoo/Xai'xais First Nation established a program to monitor sea lice levels on seaward migrating wild juvenile salmon in their traditional territory which contains the most northerly salmon farming region of British Columbia. A total of 12 locations were routinely sampled during the period between 2005 and 2008 to gain a better understanding of the levels and patterns of sea lice infestation on wild salmonids in the region. Over 5000 juvenile salmon were collected and examined for sea lice. Around 78% were identified as pink salmon, 18% were chum salmon and the remainder classified as 'other' salmon (coho and sockeye salmon). Two species of sea lice were observed: Lepeophtheirus salmonis and Caligus clemensi. Over 91% of all the juvenile salmon examined had no sea lice and there was no significant difference in L. salmonis prevalence levels among salmon species. However, chum salmon had significantly lower C. clemensi prevalence levels than either pink or 'other' salmon. There were significant annual and regional differences in L. salmonis prevalence on juvenile pink salmon; the lowest prevalence in all sampling zones occurring in 2008, while channels containing salmon farms consistently had higher levels than those without salmon farms. Mean prevalence of L. salmonis in the channels with salmon farms ranged from 2% to 9% which is lower than levels published for the same region in different years or for other areas without salmon farms. C. clemensi prevalence on wild pink salmon was associated with sampling zone and the size of pink salmon; larger juvenile fish were more likely to be infected than smaller fish. During the period of wild juvenile salmon migration, the mean abundance of motile stages of L. salmonis on farmed salmon ranged from 0.13 to 0.79 lice per fish but there were no significant differences among years. In comparison, C. clemensi abundance levels on farms were significantly higher in 2005. Factors contributing to variations in these observations are discussed

Recent Salmon Declines: A Result of Lost Feeding Opportunities Due to Bad Timing?

As the timing of spring productivity blooms in near-shore areas advances due to warming trends in global climate, the selection pressures on out-migrating salmon smolts are shifting. Species and stocks that leave natal streams earlier may be favoured over later-migrating fish. The low post-release survival of hatchery fish during recent years may be in part due to static release times that do not take the timing of plankton blooms into account. This study examined the effects of release time on the migratory behaviour and survival of wild and hatchery-reared coho salmon (Oncorhynchus kisutch) using acoustic and coded-wire telemetry. Plankton monitoring and near-shore seining were also conducted to determine which habitat and food sources were favoured. Acoustic tags (n = 140) and coded-wire tags (n = 266,692) were implanted into coho salmon smolts at the Seymour and Quinsam Rivers, in British Columbia, Canada. Differences between wild and hatchery fish, and early and late releases were examined during the entire lifecycle. Physiological sampling was also carried out on 30 fish from each release group. The smolt-to-adult survival of coho salmon released during periods of high marine productivity was 1.5- to 3-fold greater than those released both before and after, and the fish's degree of smoltification affected their downstream migration time and duration of stay in the estuary. Therefore, hatchery managers should consider having smolts fully developed and ready for release during the peak of the near-shore plankton blooms. Monitoring chlorophyll a levels and water temperature early in the spring could provide a forecast of the timing of these blooms, giving hatcheries time to adjust their release schedule

Piscine Reovirus: Genomic and Molecular Phylogenetic Analysis from Farmed and Wild Salmonids Collected on the Canada/US Pacific Coast.

Piscine reovirus (PRV) is a double stranded non-enveloped RNA virus detected in farmed and wild salmonids. This study examined the phylogenetic relationships among different PRV sequence types present in samples from salmonids in Western Canada and the US, including Alaska (US), British Columbia (Canada) and Washington State (US). Tissues testing positive for PRV were partially sequenced for segment S1, producing 71 sequences that grouped into 10 unique sequence types. Sequence analysis revealed no identifiable geographical or temporal variation among the sequence types. Identical sequence types were found in fish sampled in 2001, 2005 and 2014. In addition, PRV positive samples from fish derived from Alaska, British Columbia and Washington State share identical sequence types. Comparative analysis of the phylogenetic tree indicated that Canada/US Pacific Northwest sequences formed a subgroup with some Norwegian sequence types (group II), distinct from other Norwegian and Chilean sequences (groups I, III and IV). Representative PRV positive samples from farmed and wild fish in British Columbia and Washington State were subjected to genome sequencing using next generation sequencing methods. Individual analysis of each of the 10 partial segments indicated that the Canadian and US PRV sequence types clustered separately from available whole genome sequences of some Norwegian and Chilean sequences for all segments except the segment S4. In summary, PRV was genetically homogenous over a large geographic distance (Alaska to Washington State), and the sequence types were relatively stable over a 13 year period

Infectious Diseases Affect marine Fisheries and Aquaculture economics

Seafood is a growing part of the economy, but its economic value is diminished by marine diseases. Infectious diseases are common in the ocean, and here we tabulate 67 examples that can reduce commercial species\u27 growth and survivorship or decrease seafood quality. These impacts seem most problematic in the stressful and crowded conditions of aquaculture, which increasingly dominates seafood production as wild fishery production plateaus. For instance, marine diseases of farmed oysters, shrimp, abalone, and various fishes, particularly Atlantic salmon, cost billions of dollars each year. In comparison, it is often difficult to accurately estimate disease impacts on wild populations, especially those of pelagic and subtidal species. Farmed species often receive infectious diseases from wild species and can, in turn, export infectious agents to wild species. However, the impact of disease export on wild fisheries is controversial because there are few quantitative data demonstrating that wild species near farms suffer more from infectious diseases than those in other areas. The movement of exotic infectious agents to new areas continues to be the greatest concern

Correction: Piscine Reovirus: Genomic and Molecular Phylogenetic Analysis from Farmed and Wild Salmonids Collected on the Canada/US Pacific Coast.

[This corrects the article DOI: 10.1371/journal.pone.0141475.]

Amino acid alignment of open reading frame consensus sequences encoding the Piscine reovirus σ3 and μ1 protein.

<p>Secondary structure and transmembrane domains were predicted using EMBOSS 6.6.7 (Geneious software v6.1). Predicted secondary structure of alpha helix, beta strand, coil and turn are presented in purple cylinders, yellow arrows, grey sinusoids and blue curved arrow. Sequences are identified using the GenBank accession numbers. A/ represents ORF sequences encoding PRV σ3 amino acid alignment. Red stars are conserved Zn-finger motifs. B/ represents ORF sequences encoding PRV μ1 amino acid alignment. Red cross is myristoylation site in the MRV protein and green line is post-translational cleavage site in MRV and ARV [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0141475#pone.0141475.ref007" target="_blank">7</a>].</p

Phylogenetic relationships of Piscine reovirus sequence types derived from North American Pacific samples, a representative Norwegian and a representative Chilean sample.

<p>Samples BCJ31915_13, BCJ19943_13 and WSKFH12_14 (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0141475#pone.0141475.t001" target="_blank">Table 1</a> for sample identification) were sequenced using the Illumina platform and sequences from all 10 genome segments (L1, L2 L3, M1, M2, M3, S1, S2, S3, S4) were obtained. Sequences derived from this study are designated with bold.</p

Map of Canada/US Pacific coast showing the geographic localisations where the salmonids were sampled.

<p>AK: Alaska (United States of America); BC: British Columbia (Canada); WA: Washington State (United States of America).</p