Summary 1.Modelling the effects of environmental change on populations is a key challenge for ecologists, particularly as the pace of change increases. Currently, modelling efforts are limited by difficulties in establishing robust relationships between environmental drivers and population responses. 2. We developed an integrated capture-recapture state-space model to estimate the effects of two key environmental drivers (stream flow and temperature) on demographic rates (body growth, movement and survival) using a long-term (11 years), high-resolution (individually tagged, sampled seasonally) data set of brook trout (Salvelinus fontinalis) from four sites in a stream network. Our integrated model provides an effective context within which to estimate environmental driver effects because it takes full advantage of data by estimating (latent) state values for missing observations, because it propagates uncertainty among model components and because it accounts for the major demographic rates and interactions that contribute to annual survival. 3. We found that stream flow and temperature had strong effects on brook trout demography. Some effects, such as reduction in survival associated with low stream flow and high temperature during the summer season, were consistent across sites and age classes, suggesting that they may serve as robust indicators of vulnerability to environmental change. Other survival effects varied across ages, sites and seasons, indicating that flow and temperature may not be the primary drivers of survival in those cases. Flow and temperature also affected body growth rates; these responses were consistent across sites but differed dramatically between age classes and seasons. Finally, we found that tributary and mainstem sites responded differently to variation in flow and temperature. 4. Annual survival (combination of survival and body growth across seasons) was insensitive to body growth and was most sensitive to flow (positive) and temperature (negative) in the summer and fall. 5. These observations, combined with our ability to estimate the occurrence, magnitude and direction of fish movement between these habitat types, indicated that heterogeneity in response may provide a mechanism providing potential resilience to environmental change. *Correspondence author. E-mail: bletcher@usgs.gov Published 2014. This article is a U.S. Government work and is in the public domain in the USA Journal of Animal Ecology 2015Ecology , 84, 337-352 doi: 10.1111Ecology /1365Ecology -2656 Given that the challenges we faced in our study are likely to be common to many intensive data sets, the integrated modelling approach could be generally applicable and useful.

Electroshocking and tagging of fish with passive integrated transponder (PIT) tags are two commonly used methods for conducting mark-recapture studies in freshwater environments and are frequently used in combination. We conducted an experiment to test for the effects of electroshocking, tagging, and a combination of electroshocking plus tagging on the growth and survival of Atlantic salmon Salmo salar parr. We used five treatments that included the presence or absence of PIT tags and electroshocking at 300 or 500 V plus a control group. Fish were measured, weighed, and electroshocked on four occasions separated by approximately 2-month intervals. The average (Ϯ1 SD) fork length was 62.1 Ϯ 1.9 mm and the average weight was 2.5 Ϯ 0.3 g at the start of the experiment; at the end of the experiment, length averaged 120.5 Ϯ 11.6 mm and weight averaged 20.9 Ϯ 6.1 g. We did not detect any significant effects of electroshocking on growth or survival over the course of the experiment. However, there was evidence that tagging negatively influenced survival over the first interval after initial tagging and that survival was positively correlated with fish size. In addition, tagged fish seemed to suffer a minor depression in growth over the first interval, although differences in size among tagged and untagged fish were nonsignificant throughout the course of the experiment. We suggest that the size at tagging may have a greater effect on survival and growth of small (Ͻ80-mm) Atlantic salmon parr than the amount of exposure to electroshocking.

This paper presents first estimates of length at age, size and age at sexual maturity, and depth distributions of Atlantic halibut (Hippoglossus hippoglossus L.) off the Northeast USA. The estimates are based on samples collected from spring and autumn bottom trawl surveys in the Gulf of Maine-Georges Bank region and an experimental longline fishery off the coast of Maine (2000)(2001). Longlines targeted larger, faster growing fish than a bottom trawl indicating gear selectivity. Sexual dimorphism in growth was apparent with females attaining greater sizes after age 4. Median age at maturity was estimated to be 6.0 years for males and 7.3 years for females. Adult halibut (>80 cm) occurred at greater average depths than juveniles (<40 cm), but mean depth of capture differed among seasons for all size-classes of halibut. The results suggest that halibut from the Gulf of Maine-Georges Bank region grow faster than those from the Newfoundland-Labrador region. Median ages at maturity of male and female halibut were lower than in other regions of the Northwest Atlantic; however, lengths at maturity were similar.

A combination of a dynamic energy budget (DEB) model, field data on Atlantic salmon Salmo salar and brown trout Salmo trutta and laboratory data on Atlantic salmon was used to assess the underlying assumptions of three different metrics of growth including specific growth rate (G), standardized mass-specific growth rate (G S ) and absolute growth rate in length (G L ) in salmonids. Close agreement was found between predictions of the DEB model and the assumptions of linear growth in length and parabolic growth in mass. Field data comparing spring growth rates of age 1þ year and 2þ year Atlantic salmon demonstrated that in all years the larger age 2þ year fish exhibited a significantly lower G, but differences in growth in terms of G S and G L depended on the year examined. For brown trout, larger age 2þ year fish also consistently exhibited slower growth rates in terms of G but grew at similar rates as age 1þ year fish in terms of G S and G L . Laboratory results revealed that during the age 0þ year (autumn) the divergence in growth between future Atlantic salmon smolts and non-smolts was similar in terms of all three metrics with smolts displaying higher growth than non-smolts, however, both G S and G L indicated that smolts maintain relatively fast growth into the late autumn where G suggested that both smolts and non-smolts exhibit a sharp decrease in growth from October to November. During the spring, patterns of growth in length were significantly decoupled from patterns in growth in mass. Smolts maintained relatively fast growth though April in length but not in mass. These results suggest G S can be a useful alternative to G as a size-independent measure of growth rate in immature salmonids. In addition, during certain growth stanzas, G S may be highly correlated with G L . The decoupling of growth in mass from growth in length over ontogeny, however, may necessitate a combination of metrics to adequately describe variation in growth depending on ontogenetic stage particularly if life histories differ. Journal compilation # 2008 The Fisheries Society of the British IslesNo claim to original US government works