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There are more Pacific salmon in the ocean recently than in recorded history. Increases are believed to be related to shifts in climate but specific, biologically based mechanisms linking climate to increases are not known. At the same time, Pacific salmon abundances in Japan and on Canada's west coast are at historic low levels with attempts to stop the decline unsuccessful. Most juvenile salmon that enter the ocean die, resulting in large abundance increases and decreases from small changes in the already very low ocean survival. Because of this sensitivity to changes in ocean ecosystems and because of the recent basin-scale fluctuations in trends in abundance, I propose that it is time to see a bigger picture and improve the understanding of the biological mechanisms that most influence ocean survival. I leave it to readers to decide if my example of Pacific salmon is part of a more general need in fisheries science to better understand the biological mechanisms linking survival to climate. [ABSTRACT FROM AUTHOR]

Providing science-based advice can be challenging. Personal in its reflections, the story that follows asks throughout: What constitutes an appropriate model for the communication of science-based advice that best serves society? The first "front line," in 1992, involved tenuous hypotheses on the collapse and recovery of Newfoundland's Northern cod (Gadus morhua), raising troubling questions about political influence on science-based advice and on its integrity. These questions subsequently motivated a critique written with two colleagues on the communication of science to decision-makers, provoking a telling invective from a government department in defence of the status quo. The story transitions to my 2000–2012 tenure as a member and then as chair of Canada's national body advising which species should be on the legally binding national at-risk register, illustrating how politically sensitive science-based advice can be objectively, effectively, and independently communicated, unfiltered by vested interests. Since 2009, I have served as independent science advisor on the sourcing of sustainable seafood to Canada's largest food retailer, providing a meaningful, impactful opportunity to advise their decision-makers. Science-based advice, free from political and advocacy-driven vested interests, is a requisite return for tax-supported investments in science. If provision of such advice is a "moral imperative," as argued more than 60 years ago by C.P. Snow, then scientists are obliged to be the best advisors that we can be. [ABSTRACT FROM AUTHOR]

Northern Gannet (Morus bassanus) colonies near the species' southernmost limits are experiencing plateaued or declining population growth and prolonged poor productivity. These trends have been linked to reductions in the availability of the species' key prey, the Atlantic mackerel (Scomber scombrus). Declines in mackerel availability have been associated with warming ocean temperatures and over-fishing. Here, we assessed the influence of prey availability, abundance, and sea surface temperature (SST) during the breeding season on Northern Gannet reproductive success over a multi-decadal time span at their southernmost colony at Cape St. Mary's, NL, Canada. We demonstrate that warming SST affects reproductive success differently in early vs. late chick-rearing, but that overall, declining mackerel availability (landings and biomass) due to warming SST and over-exploitation has resulted in poor productivity of Northern Gannets at their southernmost limit. Our study is consistent with previous findings in other colonies in Atlantic Canada and France, and contrasts with findings in more northern colonies where mackerel population increases and range expansion are coinciding with gannet population growth. This implies that warming SST is having opposing influences on Northern Gannets and mackerel at the different extremes of the gannets' breeding range. [ABSTRACT FROM AUTHOR]

The fishery for Northern Atlantic cod (Gadus morhua) off Newfoundland and Labrador, Eastern Canada, presents the most spectacular case of an exploited stock crashed in a few decades by an industrial bottom trawl fishery under a seemingly sophisticated management regime after half a millennium of sustainable fishing. The fishery, which had generated annual catches of 100000 to 200000 tonnes from the beginning of the 16th century to the 1950s,  peaked in 1968 at 810000 tonnes, followed by a devastating collapse and closure 24 years later. Since then, stock recovery may have been hindered by premature openings, with vessels targeting the remains of the cod population. Previous research paid little attention towards using multicentury time series to inform sustainable catches and recovery plans. Here, we show that a simple stock assessment model can be used to model the cod population trajectory for the entire period from 1508 to 2019 for which catch estimates are available. The model suggests that if fishing effort and mortality had been stabilized in the 1980s,  precautionary annual yields of about 200000 tonnes could have been sustained. Our analysis demonstrates the value of incorporating prior knowledge to counteract shifting baseline effects on reference points and contemporary perceptions of historical stock status. [ABSTRACT FROM AUTHOR]

In North America, studies regarding effects of CO2-induced low pH in bivalve aquaculture are largely restricted to the US Pacific coast. Studies on species from the northwest Atlantic are lacking. Furthermore, information on the roles of intergenerational exposure and biological sex in bivalve responses to low pH, particularly in an aquaculture-specific context, is scant. We tested if short-term (1 month) exposure to CO2-induced reductions in pHNBS affected the reproductive development of male and female eastern oysters (Crassostrea virginica) during hatchery-specific reproductive conditioning and whether maternal and/or paternal exposure influenced larval responses. Reduced pH (7.5–7.7) increased the rate of reproductive development in both males and females. There was no indication of intergenerational effects; adult pH conditions did not affect early larval development. In contrast, low pH conditions experienced by gametes during spawning, fertilization, and embryo incubation (48 h) resulted in higher larval survival (+6–8% from control), reduced shell height (−2 to 3 µm), and increased deformities (abnormal shell shape; +3–5%). We suggest that local adaptation to acidic land runoff may account for the positive effects of low pH observed in this study. Bioeconomic assessments are now needed to understand the implications of reduced pH on aquaculture operations in these regions of Atlantic Canada. [ABSTRACT FROM AUTHOR]

The Northwest Atlantic mackerel (Scomber scombrus) population is comprised of northern and southern contingents, each with distinct natal regions in the United States and Canada. We tested hypotheses on natal origin and contingent mixing by analysing natal otolith δ18O values, evaluating the approach through an out-group comparison with the Northeast Atlantic population. Otolith δ18O values varied according to expectations between the Northeast (higher) and the Northwest (lower) Atlantic basins, and between contingents within the Northwest Atlantic stock, although contingent differences varied between years. Most adults (age-3+ years) sampled from US waters (1999–2003) represented the northern contingent (Canadian spawning site). The confirmation of the seasonal mixing of older and larger fish between the two contingents provides support and justification for the development of bi-national (United States–Canada) assessment and management of Northwest Atlantic mackerel. [ABSTRACT FROM AUTHOR]

Many ICES fish stock assessment working groups have practised Sum Of Products, SOP, correction. This correction stems from a comparison of total weights of the known landings and the SOP over age of catch in number and mean weight-at-age, which ideally should be identical. In case of SOP discrepancies some countries correct catch in numbers while others correct mean weight-at-age by a common factor, the ratio between landing and SOP. [ABSTRACT FROM PUBLISHER]

This study incorporated two pathways of environmental forcing (i.e. "larval mortality forcing" and "somatic growth forcing") into an end-to-end ecosystem model (Object-oriented Simulator of Marine ecOSystEms, OSMOSE) developed for the Pacific North Coast Integrated Management Area (PNCIMA) off western Canada, in order to evaluate alternative fisheries management strategies under environmental changes. With a suite of ecosystem-level indicators, the present study first compared the ecosystem effects of different pathways of environmental forcing scenarios; and then evaluated the alternative fisheries management strategies which encompassed a series of fishing mortality rates relative to F MSY (the fishing mortality rate that produces maximum sustainable yield) and a set of precautionary harvest control rules (HCRs). The main objectives of this study were to (i) explore the ecosystem effects of different environmental forcing scenarios; (ii) identify the impacts of different fishing mortality rates on marine ecosystem structure and function; and (iii) evaluate the ecosystem-level performance of various levels of precautionary HCRs. Results indicated that different pathways of environmental forcing had different ecosystem effects and incorporating appropriate HCRs in the fisheries management process could help maintain ecosystem health and sustainable fisheries. This study provides important information on future fisheries management options within similar marine ecosystems that are facing global changes. [ABSTRACT FROM AUTHOR]

After being extirpated from the St. Lawrence Estuary (SLE), striped bass (Morone saxatilis) were reintroduced in 2002, and by 2008 they were naturally reproducing. The increase of this reintroduced population prompted the need to document its nursery habitats utilization, which contribute to species recruitment. We analysed mortality-dispersion rates and the growth of larvae and juveniles in relation to their occurrence and migration patterns. From June to September 2014, we collected striped bass distributed in four estuarine habitats: the upstream freshwater section (UP), the oligohaline (O-ETM) and the mesohaline (M-ETM) estuarine turbidity maximum zone, and the downstream polyhaline section (DOWN). Based on otolith microstructure and microchemistry, 305 back-calculated growth and 36 migration trajectories have been reconstructed. The UP and the O-ETM provided optimal conditions wherein which larvae and juveniles exhibited fastest growth. In the SLE, we emphasized the co-existence of a freshwater resident contingent and two migrant contingents to the M-ETM and DOWN. We propose that migrants adopt an adaptive migration behaviour to avoid suboptimal conditions and strong intraspecific competition from resident in the upstream habitats. The potential advantage of a downstream migration later in the season might be an adaptative strategy to promote their survival during the early life stages. [ABSTRACT FROM AUTHOR]

Northwest Atlantic (NWA) redfish (Sebastes mentella and Sebastes fasciatus) stocks are currently assessed using survey indicators and ageaggregated production models rather than age-based models because routine age readings are not available due to the difficulty in obtaining reliable measurements for these fish. However, recruitment is highly variable for redfish species so age-aggregated production models are not a good approach to provide short-term harvest advice. Recently a relatively large dataset of validated age readings was published that provide a good basis to model growth and its variability [i.e. population growth curve (PGC)]. In this article we propose a hierarchical random effects growth model that includes between-individual variation to estimate PGCs for 10 NWA redfish stocks and for males and females separately. These growth curves are required to develop age-based stock assessment models. External estimates of measurement error in length and age are included in our model to separate these sources of variation from the PGC variability. The hierarchical approach leads to more realistic growth curves than if each stock and sex are modelled separately. Model results indicated that S. mentella usually grow to larger sizes than S. fasciatus and that females of both these species grow to larger sizes than males. There was little evidence of a change in growth rates over time. [ABSTRACT FROM AUTHOR]

According to density-dependent habitat selection theory, areas of high density can be indicative of high population productivity and have positive individual fitness consequences. Here, we explore six groundfish populations on the Scotian Shelf, Canada, where a decline in areas of high density beyond a certain threshold is associated with disproportionately large declines in Spawning Stock Biomass (SSB). This is evidenced by empirical, concave, positive relationships between high-density areas (HDAs) and SSB. We introduce a methodology to estimate the threshold below which SSB declines increasingly faster per unit of HDA decline. The spatial threshold among these six stocks was remarkably consistent; when stocks lose 70-80% of HDAs, disproportionately large SSB declines are likely to occur. We propose that spatial thresholds could serve as spatial reference points to complement existing SSB limit reference points (LRPs). For some stocks we identify spatial thresholds which correspond to SSB levels that exceed those associated with the designated SSB LRP, suggesting that a review of these SSB LRPs warrants merit. For other stocks, spatial reference points can be used in concert with SSB reference points, strengthening efforts to incorporate a precautionary approach to fisheries management. Our results warrant further research into the general application of HDA as spatial limit and target reference points for fisheries management in addition to other population status indicators within a broad recovery framework. [ABSTRACT FROM AUTHOR]

Resource managers need climate adaptation tools. We build on a popular tool, the climate change vulnerability assessment (CCVA), to identify vulnerable marine species. Only warming was considered, as warming is expected to have earlier impacts in the offshore than other climate drivers, and projections of other climate drivers are not well developed. For this reason, we coin our generalized, semi-quantitative method the "Vulnerability to Projected Warming Assessment" (VPWA) as opposed to using the broader term, CCVA. We refine the typical "exposure" component to be a function of gain/loss of thermal habitat at multiple life stages. We also build on the traditional logic approach of CCVAs. We produce scores for each species, and use a null distribution through Monte Carlo simulations to identify the most vulnerable species. We evaluate the vulnerability of 33 fish and invertebrate species, on the scale of the Scotian Shelf, Canada, to two warming scenarios, mild and severe, based on regional trends and projections. At smaller spatial scales, we evaluate populations of a subset of these species. Populations in the southwest portion of the domain are found to be more vulnerable than those in the northeast. Overall, our results indicate that 45% of populations may be vulnerable under a severe (+3°C) warming scenario, including currently endangered, threatened, and commercial populations (e.g. southwestern Atlantic cod, Smooth skate, Snow crab), while only one species has a relatively high vulnerability score under the mild (+0.7°C) scenario (Moustache sculpin). Populations triaged by relative vulnerability to regional warming should help managers prioritize resources and identify knowledge gaps. For this reason, and for its biological and ecological underpinnings, our method has broad relevance within the marine science and management field. As more information become available, our VPWA can be used as a stepping-stone in the continued development of CCVA methods. [ABSTRACT FROM AUTHOR]

By leading the Canadian Fisheries Expedition of 1914–1915 Johan Hjort took the opportunity to do far more than just survey herring, other fish stocks, and the hydrography of Canadian Atlantic waters. He also attempted to improve the backward fish-processing technologies used in the local fisheries, an agenda blocked by the Canadian government. Hjort did succeed markedly, however, in introducing Canadian scientists to the International Council for the Exploration of the Sea's new scientific methods for fisheries research. He and his colleagues offered training in the new dynamic oceanography as well as population demographic studies and biometrics for studying fish populations, races, and other units. His extroverted leadership-initiated lasting linkages between Canadian and Scandinavian scientists, and created an international network of fisheries biologists. [ABSTRACT FROM AUTHOR]

Zwolinski, J. P., and Demer, D. A. 2013. Measurements of natural mortality for Pacific sardine (Sardinops sagax). – ICES Journal of Marine Science, 70: .The northern stock of Pacific sardine (Sardinops sagax) in the California Current Ecosystem is periodically assessed to provide harvest guidelines for the United States and Canadian fisheries. The assessment model incorporates the estimates of abundance from acoustic-trawl method (ATM) and other surveys and many parameters including a constant value for the instantaneous natural mortality coefficient (M). Here, the ATM-estimated length-structured sardine abundances for 2006–2011 are combined to directly estimate M. The stock was dominated by the 2003, 2004, and 2005 year classes (2003–2005 cohort) from 2006 to 2010 and by the 2009 and 2010 year classes in 2011. Insignificant recruitments during 2006–2010 allowed the 2003–2005 cohort to be tracked and M to be estimated. The bootstrap distributions of estimated M encompass the assessment-assumed value of 0.4−year. The measurements suggest that M is high for a new cohort, declines during mid-life, then increases as the fish approach their longevity. The mean M for the entire period, 0.52, is 30% higher than the one currently assumed for the assessment, reflecting the steeper decline in the ATM-estimated biomass versus that in the assessment model. [ABSTRACT FROM PUBLISHER]

Malyshev, A., and Quijón, P. A. 2011. Disruption of essential habitat by a coastal invader: new evidence of the effects of green crabs on eelgrass beds. – ICES Journal of Marine Science, 68: 1852–1856.Eelgrass (Zostera marina) beds have been declining in Atlantic Canada and elsewhere, partly as a result of sediment disruption and direct feeding/cutting of basal meristems by the green crab (Carcinus maenas). Green crabs are detrimental to eelgrass beds, and field and laboratory experiments have confirmed that the deleterious role of this invasive species is mediated by at least two mechanisms, depending on the size/age of the crabs: uprooting by adults and grazing by juveniles. Eelgrass uprooting and grazing by green crabs are likely to contribute to further declines or a lack of recovery of eelgrass beds. [ABSTRACT FROM PUBLISHER]

Ricard, D., Branton, R. M., Clark, D. W., and Hurley, P. 2010. Extracting groundfish survey indices from the Ocean Biogeographic Information System (OBIS): an example from Fisheries and Oceans Canada. – ICES Journal of Marine Science, 67: 638–645.Scientific trawl surveys have been conducted in different regions of the world and by a variety of countries and agencies since the mid-1900s. Although the data are collected in a scientifically and statistically appropriate context and represent an important source of fishery-independent information for agency-specific stock assessments, their use and dissemination has often been limited to the agencies conducting the surveys. In recent years, Internet data portals such as the Ocean Biogeographic Information System have provided an arena for the wider distribution and use of marine fish data. Despite the increased accessibility of such data, their scientific acceptability has been limited by a lack of reproducibility in data analyses. We present a methodology for the computation of time-series of groundfish stock indices using publicly available trawl survey data derived from the Canadian Department of Fisheries and Oceans Maritimes region. Potential pitfalls associated with the computation of time-series are discussed and proper stratified random estimates of temporal abundance trends are compared with other methods for a selected subset of species. Also, the broader applicability of the methods for datasets collected under similar sampling designs is discussed, along with the reproducibility of the analyses and results. [ABSTRACT FROM PUBLISHER]

Leaper, R., Lavigne, D. M., Corkeron, P., and Johnston, D. W. 2010. Towards a precautionary approach to managing Canada's commercial harp seal hunt. – ICES Journal of Marine Science, 67: 316–320.The Canadian government's approach to the management of its commercial harp seal hunt is compared with other precautionary approaches developed for setting anthropogenic removal limits for marine mammal populations. For Canada's harp seal hunt, the current management strategy has not been fully specified or tested, and its robustness to changes in biological parameters, uncertainty in input data and environmental variability, remains unknown. As such, the management approach cannot be considered precautionary and there is a substantial, but not quantified, probability that it will not meet its objectives. There is an urgent need for a fully specified and rigorously tested management procedure, and steps towards this are suggested that should reduce the risks associated with the current approach. [ABSTRACT FROM PUBLISHER]

Hay, D. E., McCarter, P. B., Daniel, K. S., and Schweigert, J. F. 2009. Spatial diversity of Pacific herring (Clupea pallasi) spawning areas. – ICES Journal of Marine Science, 66: 1662–1666.Eastern Pacific herring spawn in intertidal and shallow subtidal areas. Spawning sites are conspicuous: milt turns coastal waters white, sometimes for distances of many kilometres. This attribute has enabled biologists to document spawning distributions for more than 70 years throughout the 29 500 km coastline of western Canada. Spawning distributions and spatial diversity have varied over time. When aggregated over 70 years (1938–2007), spawning occurred along 5574 km or ∼20% of the total coastline. Cumulative annual spawn length ranges from 131 (in 1966) to 770 km (in 1992). We examined annual changes in spawn distribution using spatial units of variable size, ranging in area from a maximum of >1000 km2 to a minimum of <0.1 km2. Assessment of spatial diversity varied with the size of the spatial unit. Spatial diversity estimated from small spatial units (area <0.1 km2) was significantly correlated with spawning-stock biomass (SSB). In contrast, there was no correlation, and sometimes opposite temporal trends, between SSB and all larger spatial units (mean area >0.3 km2). The choice of spatial scale can affect the results from analyses of other factors, such as SSB, that could affect spatial diversity of spawning areas. [ABSTRACT FROM PUBLISHER]

McPhie, R. P., and Campana, S. E. 2009. Bomb dating and age determination of skates (family Rajidae) off the eastern coast of Canada. – ICES Journal of Marine Science, 66: 546–560.Recent declines in abundance of skates off the eastern coast of Canada have heightened the need for validated age and growth estimates in the region. In all, 502 winter (Leucoraja ocellata), little (Leucoraja erinacea), thorny (Amblyraja radiata), and smooth (Malacoraja senta) skate vertebral centra collected seasonally between 1999 and 2004 were sectioned using a mass processing method, then used to reconstruct growth in each species. Bomb radiocarbon (Δ14C) analysis was used to provide evidence of annual band-pair deposition in thorny skates. Estimates of L∞ from traditional von Bertalanffy growth models (VBGM) ranged from 60.6 cm (little skate) to 89.7 cm (thorny skate), and K estimates from 0.07 (thorny skate) to 0.19 (little skate). A modified two-parameter VBGM (Lmax = 94.1 cm) fitted to winter skate length-at-age data yielded a value of K of 0.15. Maximum observed ages ranged from 12 (little skate) to 19 years in both winter and thorny skates. The year-specific incorporation of Δ14C milled from thorny and winter skate vertebral sections closely resembled shark-derived reference chronology values from the Northwest Atlantic. Pre-bomb Δ14C in a thorny skate collected in 1988 and aged at 23 years appeared to validate age interpretations and suggested that thorny skate reach an absolute age of at least 28 years, the oldest validated age reported for any species of batoid. [ABSTRACT FROM PUBLISHER]

Mercer Clarke, C. S. L., Roff, J. C., and Bard, S. M. 2008. Back to the future: using landscape ecology to understand changing patterns of land use in Canada, and its effects on the sustainability of coastal ecosystems. – ICES Journal of Marine Science, 65: 1534–1539.In Canada, concerns are mounting that the coastal environments may be more affected by human activities than is evidenced by current monitoring and assessment of environmental quality. Holistically orientated approaches to coastal management have concluded that indicators of coastal sustainability must include a wider array of factors that go beyond marine ecosystem health to include the health and well-being of coastal terrestrial environments and human communities. Research is needed to bridge the disciplinary and jurisdictional barriers that hamper better understanding of the relationships between terrestrial and marine ecosystems, and to help recognize the role of humans as both a contributing and an affected species in the coastal ecotone. Our examination of past and current knowledge of conditions along the Atlantic shore of Nova Scotia led us to challenge the predominant view that all is well along Canadian coasts. Using an interdisciplinary approach derived from landscape ecology, we examined international, national, and local efforts to assess management indicators against factors that gauge their relevance to marine- and land-development planning and management. We propose a new context for indicators, one that challenges scientists to provide decision-makers with information that can be used to drive social change, avoiding or mitigating human activities and sustaining coastal ecosystems. [ABSTRACT FROM PUBLISHER]

Yellowtail flounder (Limanda ferruginea) (Storer, 1839) on the Grand Bank off Newfoundland were traditionally aged using surface-read whole otoliths. Age determination of otoliths from recaptures of fish tagged in the early 1990s indicated that the traditional ageing technique was underestimating the ages of yellowtail flounder when compared with the time at liberty. Age comparisons between whole and thin-sectioned otoliths showed agreement in age readings up to 7 years; thereafter whole otoliths tended to give much lower ages than those estimated by thin sections. Length–frequency analysis of pelagic and demersal juveniles, captive rearing of juveniles and marginal increment analysis all corroborated age determination based on thin sections. Tag-recaptures and bomb radiocarbon assays validated age interpretations based on thin sections in young and old yellowtail flounder, respectively. Ages were validated up to 25 years for females and 21 years for males. However, because of increased narrowing of annuli in thin-sectioned otoliths from old fish, even thin sections may underestimate the true age of the fish. von Bertalanffy growth curve parameters (combined sexes) were L∞=55.6 cm total length, K=0.16 and t0=−0.003. These results challenge the conventional view that yellowtail flounder on the Grand Banks are a relatively fast growing, short-lived species. [Copyright &y& Elsevier]

The extant, coastal northern cod (Gadus morhua) have over-wintered and spawned in Smith Sound, Newfoundland, since 1995, and acoustic surveys have been conducted in several seasons since then. Cod move into the Sound in late fall, over-winter in a dense, size- and age-structured aggregation, spawn between late March and early June and then disperse into and beyond Trinity Bay during summer to feed. The optimal survey time for biomass estimation is January–February, when the waters are ice-free and the cod are in mono-specific, relatively stationary, and well-defined aggregations with the highest densities and are typically clear of “bottom returns”. Biomass surveys have been conducted in mid-January since 1999. An error analysis indicated the main sources of uncertainty to be density variability and target strength (TS). Repeated quasi-synoptic (10 h) surveys were the optimal means of producing an estimate of uncertainty about population size. Some vertical movement led to night-time surveys consistently having higher estimates than day-time surveys by approximately 15%. Detectability ranged from 73 to 86% and deadzone-corrected, acoustic measures did not differ from swept-area densities found by bottom trawling. Biomass scaling by TS used length-dependant dB/kg to reduce the size-sampling error. Overall, population biomass doubled in approximately 7 years, consistent with a rate of increase around 0.2, largely through recruitment. The surveys are internally consistent and indicate instantaneous rates of mortality among year classes of 0.3 to >2 (very high on older fish) and provide a method for monitoring the annual biomass (cv<40%). [Copyright &y& Elsevier]

Trophic interactions among seabirds and capelin (Mallotus villosus), a key forage species off Newfoundland and Labrador, are examined. During the 1990s, estimates of relative year-class strength of capelin were similar to estimates in the 1980s, capelin spawned later and matured younger, mean fish size was smaller, and there were large-scale distributional shifts of capelin. Most of these changes were linked to below-normal sea temperatures during the early 1990s, but the changes have persisted even though temperatures have returned to normal. Seabirds bred later in the 1990s and changed diets and foraging strategies. Off eastern Newfoundland, the breeding success of black-legged kittiwakes declined during the early 1990s owing to a suite of factors, including their inability to dive to capture capelin, the late arrival of capelin inshore and predation by gulls. Common murres and puffins did not suffer breeding failures because they could dive and catch capelin at depth. Off Labrador, black-legged kittiwakes experienced breeding failures because of the lack of capelin while common murres were able to find alternate prey and bred successfully. The diets of gannets in the 1990s contained a higher proportion of cold-water prey than in earlier periods when warm-water prey predominated. The population sizes of all seabird species remained stable or increased, with the exception of gulls. Increasing populations of seabirds are related in part to their lessened mortality from gillnets since the closures of the eastern Canadian groundfishery in 1992, whereas declining populations of gulls can be related to reduced food availability from fishery discards and offal. This food limitation has led gulls to switch much of their foraging effort from scavenging to predation on seabird adults and chicks before capelin arrive inshore. Crown Copyright 2002 Published by Elsevier Science Ltd on behalf of International Council for the Exploration of the Sea. All rights reserved. [Copyright &y& Elsevier]

The stock of northern cod (Gadus morhua) off Newfoundland and Labrador is at its lowest level in recorded history, with no rebuilding of northern spawning aggregations since the fishing moratorium in 1992. Cod diet was historically dominated by capelin (Mallotus villosus), which have been scarce in the northern areas since 1990. Using the study areas Hawke Channel and Trinity Bay within the historical northern cod range, and Placentia Bay (south coast), we examine growth, condition, and reproductive potential with respect to capelin diet in 18 000 cod sampled primarily in January and June of the years 1996–2000. Overall diet weights differed among areas and seasons (Placentia=Hawke>Trinity in January; Placentia>Trinity=Hawke in June). However, just 7 of 3383 cod stomachs (0.2%) from Hawke contained capelin (PFI=0). In contrast, 10% of cod of ages 3–7 in Placentia and Trinity Bays preyed on capelin and overall capelin partial fullness indices (PFI) were 0.2–0.4. Capelin PFIs were correlated with an index of availability (potential contact of capelin within 40 km of cod) calculated from acoustic surveys. Seasonally adjusted cod liver condition was strongly associated with capelin availability (p<0.05), and the liver index was highly correlated with gonad size in mature females (especially 4–6-year-olds). The links between capelin availability and cod diet, growth, condition, and reproductive potential suggest that cod rebuilding requires capelin and tends to mirror capelin distribution (Placentia>Trinity≫Hawke).Copyright 2002 International Council for the Exploration of the Sea. Published by Elsevier Science Ltd. All rights reserved . [Copyright &y& Elsevier]

Vertical distribution patterns of capelin were examined using data from spring and autumn acoustic surveys off northeastern Newfoundland in the years 1988–2000. Until 1991, capelin typically underwent diel vertical migrations from 50 to 150 m. Since 1991, vertical migrations have been reduced or have become erratic, with capelin commonly located deeper in the water column (200+m) and closer to the seabed. Changes in vertical distribution initially coincided with the onset of a severe cold period, but distributions failed to return to normal as waters warmed. Vertical distribution was examined with regard to potential habitat-selection factors, including capelin density, water temperature, fish size, maturity stage, and proximity of predators. Of these, only fish density and predator (Atlantic cod) presence were significant. Capelin occupied more of the water column when their density was high than when it was low, and they were found farther from the seabed in areas with cod than without. Results indicate that, during the 1990s, capelin should have been able to optimize vertical distribution and feeding. This is not consistent with reports of poorer capelin condition and size-at-age in the 1990s, suggesting that vertical distributions are likely a result of changes in other factors, such as prey availability. Crown Copyright 2002 Published by Elsevier Science Ltd on behalf of International Council for the Exploration of the Sea. All rights reserved. [Copyright &y& Elsevier]

Condition factors (Fulton''s K and predicted weight-at-length) were determined for male and female Newfoundland capelin, Mallotus villosus (Mu¨ller), for the years 1982–1999, a time of major change in the ecosystem. Predicted weight-at-length showed the same trend as length-specific K for both males and females, so validating the use of K, even though the value of b deviated from 3. K at the population level was generally higher during the 1980s than during the 1990s. In addition, length-specific K tended to increase with length within years for both males and females. Length-specific K for males, when expressed as anomalies from the long-term mean, was higher and more variable than for females. The relationships between length-specific K anomalies and water-temperature anomalies were not significant and were a mixture of both positive and negative sign. There were weak, negative relationships between population condition for both sexes and spawning biomass, suggesting that future research should focus on density-dependent influences on K. There were no significant relationships between condition and stock productivity, expressed as recruitment and survival rate. Given the importance of environmental variability to stock productivity, as previously documented for capelin, maternal effects may be of only secondary importance. Crown Copyright 2002 Published by Elsevier Science Ltd on behalf of International Council for the Exploration of the Sea. All rights reserved. [Copyright &y& Elsevier]

Wind conditions during the period of larval drift of capelin are examined in relation to indices of larval drift and recruitment of the species over the five years 1982–1986 in Trinity Bay, Canada. Capelin larvae were abundant during all surveys except that of July 1985, when spawning was late as a result of cooler environmental conditions. Abundance of larvae was positively correlated with subsequent recruitment and inversely correlated with the time interval between northeasterly winds following spawning. Larval transport was mainly across (from northwest to southeast) and out of the bay, away from the spawning beaches. Larval transport itself was positively correlated with both the intensity of Ekman transport and a cumulative measure of wind-forcing in July, but it was negatively correlated with a measure of variability in wind speed and direction. The wind indices were related to measures of recruitment, but their slopes were opposite in sign to those observed between them and larval transport. There was no obvious relationship between larval transport and recruitment, i.e. transport of capelin larvae out of Trinity Bay was not a necessary requirement for successful recruitment. Our data are consistent with the hypothesis that wind-generated turbulence in the upper layers of the water column can modulate survival and recruitment. CrownCopyright 2002 Published by Elsevier Science Ltd. on behalf of International Council for the Exploration of the Sea. All rights reserved . [Copyright &y& Elsevier]

Juvenile capelin, Mallotus villosus (Mu¨ller), were distributed primarily on the northern Grand Banks and secondarily along the northeast coast of Newfoundland during late summer, 1994–1999. In some years, distributions extended to coastal Labrador. Capelin were seldom observed over deep water of the northeast Newfoundland Shelf or in shallow water of the southern Grand Banks. There were large areas encompassing wide ranges of capelin densities measured by the IYGPT trawl where the acoustic system did not detect capelin. Mean growth rate of capelin from 0- to 2-group was represented by length (mm)=90.9 age (years)0.57 (r2=99%). The 1-group capelin formed discrete schools that varied significantly in fish length from 65 to 110 mm (p<0.05). Spatially, the different size groups occurred at scales of <55 km and possibly <3 km in some cases. The geographic distribution of age groups was not a simple function of cohort abundance. Capelin were distributed primarily in the middle ranges of temperature (5–8°C) and zooplankton biomass (2–4 g dry weight m−2) sampled during the surveys. It is possible that interspecific competition limits the distributions of juvenile capelin, where juvenile Arctic cod (Boreogadus saida) and sandlance (Ammodytes sp.) were abundant to the north and south respectively. Copyright 2002 International Council for the Exploration of the Sea. Published by Elsevier Science Ltd. All rights reserved. [Copyright &y& Elsevier]

We postulate that the variation in capelin, Mallotus villosus (Mu¨ller), egg concentration among spawning beaches in eastern Newfoundland is a function of beach characteristics. This hypothesis is explored by examining relations between egg concentration and beach characteristics among 15 beaches located around the perimeter of Conception Bay. Beaches ranged in mid-tide area from 300 to 8000 m2, in shore-normal orientation from 20 to 330°, in median grain size from 2.4 to 11.3 mm, and in egg concentration from 360 to 4380 cm−2 mid-tide zone. Variations in beach sediment grain-size distributions were captured by variations in the overall rate constant (k) and inflection point (I) of the logistic equation fitted to the cumulative percentage grain-size distributions. Beach orientation explained 57% of the variation in egg concentration among beaches. Orientation and k explained 61% and additional exploratory models explained 80–86% of the variation. Our findings build upon previous reports that describe the significance of the physical environment on the early life history of capelin and provide a quantitative method for classifying the spawning habitat of beach-spawning capelin. Crown Copyright 2002 Published by Elsevier Science Ltd on behalf of International Council for the Exploration of the Sea. All rights reserved. [Copyright &y& Elsevier]

In situ acoustic target strength (TS) experiments were conducted on Atlantic redfish (Sebastes spp.) in Newfoundland waters (1996–1998) using deep-tow dual beam and hull-mounted split beam echosounders (38 kHz). The dual and split beam mean TSs did not differ. The deep-tow system was deployed at various depths over several aggregations. Calibration corrections were made for depths from 5–70 m (<1 dB). The TS declined at ranges <50 m from the top of the fish shoal suggesting avoidance behaviour. It was biased upward at ranges >200 m and a number of fish per sampled volume >0.04. After being controlled for variations related to range, reverberation volume and fish density the TS did not differ with respect to depth, distance from bottom, fish sex ratio, condition factor or weight. The mean length was the dominant influence on the mean TS. Pooled ex situ experimental data and controlled in situ data – which did not differ – indicated a length-based regression (weighted by s.e.−1) in standard format: TS=20 log [length (cm)] −68.7 (r2=0.49). Copyright 2002 International Council for the Exploration of the Sea. Published by Elsevier Science Ltd. All rights reserved. [Copyright &y& Elsevier]

The growth, length at age, time of spawning, food, and movements of the genetically distinct, resident northern Atlantic cod (Gadus morhua L.) in Gilbert Bay, Labrador, were studied over four consecutive years (1998–2001). Angling and plankton nets were used to sample all stages of the life history. During the study, 2453 cod were tagged with Floy t-bar tags, but none were recaptured outside the bay. Length-at-age is smaller than those of other Atlantic cod off Newfoundland and Labrador. Males mature at 31.0–35.5 cm total length (TL) and 4–6 years of age, and females at 31.4–42.1 cm, 4–8 years of age. Spawning starts shortly after ice retreats from the bay, usually in mid-May, and lasts for ∼3 weeks, a much shorter duration than reported for other northern cod. Timing appears critical to the retention of spawning products in the bay. Stomach contents indicated a wide range of benthic prey but that food availability may be low, contributing to the slow growth rate, individual cod targeting a small number of prey types. Gilbert Bay cod could be threatened if they continue to be managed as part of the Newfoundland–Labrador northern cod stock. Copyright 2002 International Council for the Exploration of the Sea. Published by Elsevier Science Ltd. All rights reserved. [Copyright &y& Elsevier]

The closure of the cod fishery in Canada's southern Gulf of St Lawrence, and the existence of a reliable research vessel (RV) survey of the stock, has provided a unique opportunity to directly estimate the instantaneous rate of natural mortality (M) of a commercial cod stock. The results indicate that M is currently in the range of 0.4, which is higher than the value of 0.2 assumed in the past. An M of 0.4 is not inconsistent with the observed age range of cod in commercial catches and with recent growth characteristics of the stock. There is evidence that M may have increased in the early 1980s. [ABSTRACT FROM PUBLISHER]

The process of developing and implementing decision rules resolved a mixed-stock herring fishery crisis in Cape Breton, Nova Scotia, Canada. The fishery occurs in an area which receives a large migrating stock on a set of smaller local stocks. A purse seine fleet follows the migrating stock into the area as part of their autumn and winter fishery. Little is known about the smaller local stocks which are harvested as by-catch in the seiner fishery and in directed inshore fisheries by local boats. A situation of constantly shifting regulations during the 1996 fishing season led to a series of incidents that included a wharf occupation and prevention of seiner offloading. As a result of these conflicts it was decided to develop decision rules that would allow the fishery to continue in a safe manner and would clearly identify the information and analyses needed to change the rules. [ABSTRACT FROM PUBLISHER]

High numbers of non-maturing, cultured Atlantic salmon that escaped after one winter in sea-cages ascended into fresh water in the Magaguadavic River, New Brunswick. Acoustic telemetry was used to investigate the movements and behaviour of 14 of these fish in the river over the natural spawning period. Four of the fish remained in deep, slow areas within 1 km of the dam, five moved less than 10 km upstream, and five moved no further than 17.5 km. They then remained at these sites for the rest of the study. Thus, all fish failed to reach the known spawning areas located further upstream. It is presumed that the limited movement of the cultured fish was related to their failure to sexually mature. Why these non-maturing salmon entered fresh water remains unanswered, but their residence in the river could have ecological implications. [ABSTRACT FROM PUBLISHER]

The origin of Atlantic salmon (Salmo salar) in the smolt migration from the Magaguadavic River, New Brunswick, was examined to assess the importance of losses of juveniles from hatcheries and the potentialimpact on the wild stock. Three hatcheries that produce over two million smolts annually for the aquaculture industry are located along the river. Smolts were sampled at the mouth of the river over a 1-month period. Two methods were used to determine their origin: (1) external appearance of fins and size at a given age, and (2) a discriminant function analysis comparing number of circuli in the first year on scales and back-calculated length at age 1 to those of fish of known wild and hatchery origins. The two methods indicated that 23.4–39.6% of smolts were of wild origin, 9.4% were hatchery releases, and 51.0–67.2% were juvenile escapees. The fin and size method predicted that more smolts in the run were of escaped hatchery origin than classified by the discriminant function analysis. Many of these were large 1-year-old smolts. Smolts of hatchery origin were significantly larger than wild smolts and could benefit from increased early marine survival. This study indicates that the potential impact of juvenile salmon that escape or are accidentally released in rivers has probably been underestimated. [ABSTRACT FROM PUBLISHER]

PIROP (Programme Intégré des Recherches sur les Oiseaux Pélagiques) is a well-known and unique database for seabird observations collected from the whole eastern Canadian coast, from the Gulf of Maine to the Canadian Arctic, and some other regions, between 1966 and 1992. Although several major seabird studies have already used the PIROP data, the potential exists for further data analysis. This is particularly true for statistical analyses of seabird distribution in relation to oceanographic data. Collection of field data for PIROP has evolved and improved over a period of 20 years, and new software for data entry has been developed that allows for quick and efficient entry of data on seabird observations made at sea. Thus, advanced data analysis, including spatial analyses using Geographical Information Systems (GIS), can now be done. Data may be analysed, imported and exported, and previously compiled data-sets can also be implemented into the PIROP scheme using data conversion algorithms in the import feature of the new PIROP software system. Using the new software system, an example of an analysis of the PIROP data is presented. Positive sightings of northern gannets (Sula bassana) and northern fulmars (Fulmarus glacialis) in the month of August were extracted and analysed in relation to sea depth data derived from a digital database (ETOPO5). A Classification and Regression Tree (CART) was used as an exploratory data analysis method, indicating how a distri-bution model for gannets versus fulmars in relation to sea depth may be derived from these data-sets. The model suggests that fulmar observations occur north of 51.57°N latitude over both shallow and deep waters. South of 51.57°N latitude, fulmars are found over waters deeper than 203 m, while gannets are found over shallow regions less than 203 m deep. This result is probably due to the preponderance of non-breeding birds among the observed fulmars, whereas gannets are confined to the vicinity of breeding colonies, which are situated on the continental shelf. [ABSTRACT FROM PUBLISHER]

We examined the history of exploitation of three cod populations in Eastern Canada since 1954 as estimated from tag return data from 122 tagging experiments. We found very high rates of exploitation in the late 1980s and early 1990s that are consistent with the hypothesis that these populations collapsed because of overfishing. The estimates were made with a new method that incorporates the data in the year of tagging which are often ignored. [ABSTRACT FROM PUBLISHER]

A joint Japanese/Canadian research cruise was carried out during May and June 1994 off the west coast of Canada to obtain two independent estimates of the in situ target strength (TS) of Pacific hake (Merluccius productus). Two vessels with independent quantitative echosounder systems were used. One was equipped with 120 and 50 kHz transducers, while the other used 38 kHz. The 120 kHz transducer featured a quasi-ideal beam pattern with a relatively flat response near the beam axis and low side lobes. Different single-beam TS estimation procedures were used to estimate TS from either system. Fish targets were identified by midwater trawling on the same or the next day. On one occasion both vessels were used to fish and measure TS simultaneously. The observed mean night-time TS for adult hake ranged from −36.4 to −30.4 dB kg−1. [ABSTRACT FROM PUBLISHER]