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The life history of North American Atlantic salmon ( Salmo salar) is characterized by extensive round-trip migrations between freshwater rearing habitats and marine feeding grounds off the coasts of Canada and Greenland. Growth is rapid during the marine migration, and growth rate and condition factor may be indicators of salmon health during this period. Growth data were evaluated from a tag-recovery program conducted from 1969 to 1991 using hatchery-reared Atlantic salmon smolts released in the Penobscot River, Maine, U.S.A. Information from recaptures of 3167 salmon that were at large in the marine environment for 1 month to 3 yr was analyzed. Length-weight measurements coupled with time-at-large data were used to estimate von Bertalanffy and allometric growth parameters specific to the marine phase. Variations in growth and condition factor in relation to smolt age, release date, and temperature conditions in the northwest Atlantic were also examined. The von Bertalanffy k parameter declined with ordinal release date, indicating faster growth rates during the first year of smolts released earlier in the spring. The 2-yr-old smolts had a larger k than 1-yr-old smolts, although 1-yr-old smolts grew to a larger asymptotic size. Sea surface temperature had variable effects on growth parameters and condition factor, with temperature at the beginning of the migration and in overwintering habitat during the first year at sea having the greatest influence on length-weight relationships. Determining the mechanisms that influence growth of individuals during the marine phase will help elucidate the factors responsible for historic growth trends, establishing a baseline for current research. [ABSTRACT FROM AUTHOR]

Miller, A. S., Sheehan, T. F., Renkawitz, M. D., Meister, A. L., and Miller, T. J. 2012. Revisiting the marine migration of US Atlantic salmon using historical Carlin tag data. – ICES Journal of Marine Science, 69: 1609–1615.The development of a fishery for Atlantic salmon (Salmo salar) in the sea at West Greenland in the early 1960s prompted the start of a US tagging programme in 1962. Between 1962 and 1996, more than 1.5 million salmon from New England rivers, primarily hatchery-reared smolts, were tagged and released. Overall, the rate of tag recovery was 0.55%, with 23.2% of the tags recovered from Canada, 26.0% from Greenland, and 50.8% from the United States. A generalized additive model was used to analyse marine survival based on returns of tagged salmon to the Penobscot River. The month and year of release, sea age, smolt age, and environmental variables, such as the North Atlantic Oscillation (NAO) and Atlantic Multidecadal Oscillation (AMO) indices and local sea surface temperatures (SSTs), were assessed to explain the variability in the return rate. The AMO and NAO indices, SST, sea age, and time across years all affected survival assessed in terms of returns to the Penobscot River. The results provide information to support the management of Atlantic salmon stocks on a spatial and temporal scale in US rivers and the fishery at West Greenland. [ABSTRACT FROM PUBLISHER]

Sheehan, T. F., Reddin, D. G., Chaput, G., and Renkawitz, M. D. 2012. SALSEA North America: a pelagic ecosystem survey targeting Atlantic salmon in the Northwest Atlantic. – ICES Journal of Marine Science, 69: 1580–1588.Pelagic ecosystem surveys were conducted in the Labrador Sea during 2008 and 2009 as part of SALSEA North America. In total, 107 Atlantic salmon (Salmo salar) were captured using a pelagic surface trawl and multipanel surface gillnets. Surface trawling provided a broad spatial sampling of the fish and macroinvertebrate communities in the upper 10 m of the water column, but caught few salmon (23). Gillnetting was more effective at capturing post-smolt (60) and adult (24) salmon. Multiple smolt cohorts were captured, indicating that post-smolts and returning adults from different rivers in North America have similar autumnal habitat requirements. Post-smolts were caught at night and in water temperatures exceeding 10°C, both novel results. Post-smolts and adults consumed similar and diverse prey species, although Themisto compressa was the most important prey item. Intestinal macroparasite loads were substantial and could be a significant source of mortality. Concurrent planktonic assemblage and oceanographic conditions were also quantified. A full exploration of these data, historical datasets, and parallel data collected during SALSEA Greenland and SALSEA-Merge will further understanding of the ecology of marine-phase Atlantic salmon and inform investigations into stock-specific differences in marine productivity. [ABSTRACT FROM PUBLISHER]

To gain information on postsmolt dynamics of emigrating Atlantic salmonSalmo salarthrough Penobscot Estuary and Penobscot Bay, Maine, we conducted a telemetry experiment in 2005. We implanted 26 salmon smolts with ultrasonic depth tags, and monitored movement activity and fish passage with linear detection arrays through 44.2 km of the estuary and 45.5 km of the bay. During daylight in the bay, greater than 95% of the detections occurred in water depths of 5 m or less, but depths to 37 m were recorded. At night, 99% of the detections were in the top 5 m of the water column and maximum depth was 9 m. Overall survival was 39% and was highest for smaller fish and those released earlier in the smolt run, when river discharge was greater. Rapid emigration (i.e., approximately 1 km/h) and preferential surface orientation improved survival. These results verify that postsmolts are primarily surface oriented in the waters of Penobscot Bay and that they may experience high rates of nearshore mortality despite their short residence time. Detailed emigration and behavioral data such as these allow scientists and managers to delineate areas of high mortality to develop strategies that improve survival, and provide marine spatial planners information to minimize impacts of coastal zone development. Received November 28, 2011; accepted April 19, 2012 [ABSTRACT FROM PUBLISHER]

Atlantic salmon Salmo salar of U.S. hatchery origin were captured as postsmolts by surface trawling during spatial surveys in late May to mid-June in the northeastern Gulf of Maine in 2002 and 2003. Most marked and unmarked postsmolts were from the Penobscot River, but some were also from the Dennys and other rivers of the Gulf of Maine. The capture rate of stocked smolts was very low (≤0.01%), and it was highest for marked smolts from known rivers and proportional to numbers stocked. Marked postsmolts were caught 16–43 d after their release as smolts and 89–240 km from their river of origin. The rate of migration from different rivers differed and varied annually, and it accounted for some of the observed differences in capture rate. The weight of postsmolts from known rivers was greater than at smolt stocking and river exit, indicating early marine growth. The distribution of U.S. postsmolts from different rivers was similar, and they were often caught together, as were those from the same river. As a result of this close association during migration, postsmolt catches were aggregated at a few adjacent locations in several areas of the Gulf of Maine. Postsmolts crossing the Gulf of Maine were found east of Jordan Basin and most were along a corridor near shore at the eastern edge of the area surveyed along the southwest coast of Nova Scotia, Canada. Postsmolts of U.S. origin were found in areas used by other salmon populations also leaving the Bay of Fundy during May and June. This seasonal occurrence in a specific coastal area provides an opportunity to manage activities within that corridor to mitigate potential losses of Atlantic salmon from endangered and threatened populations in North America. Received August 30, 2011; accepted January 16, 2012 [ABSTRACT FROM PUBLISHER]

We evaluated detectability of visual implant elastomer (VIE) tags in individual Atlantic salmon Salmo salar reared from smolts to adults in commercial marine net-pens. A total of 9,000 individual smolts were marked (adipose eye, lower jaw, or both) with colored VIE tags. During the period from March 1998 to December 2000 (2-28 months after tagging) a total of 3,220 fish were visually inspected for VIE tags. Tag detection rates remained high (>90%) for the first 17 months after tagging but then declined sharply, particularly for VIEs in the jaw. Use of a UV light significantly increased detection of both eye and jaw VIE tags. We conclude that VIE tags are optimal for use in Atlantic salmon when recovery of fish occurs within 17 months of tagging. [ABSTRACT FROM AUTHOR]