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The anadromous alewife is a commercially fished clupeid in Atlantic Canada, whose oceanic migration is poorly understood. Migration of alewives is presently investigated from the lower reaches of Gaspereau River into Minas Basin, Bay of Fundy. Seventy-five post-spawning adults were tagged on their downstream migration; within two days of being tagged, most alewives had left Gaspereau River and 57 entered into the Southern Bight of Minas Basin. Thirty-one alewives were detected in Minas Passage and their average time from tagging to final detection was 28 days with standard deviation of 11 days. None of the alewives were detected in Minas Passage until day 20 after the start of tagging. After day 20, the residence timescale in Minas Basin was only 8.8 days with 95% CI of 8.4–9.3 days. Fast tidal currents prevail in much of the study area, and alewives travelled many large tidal excursions in Minas Basin and Minas Passage. Separation distances between pairs of alewives increased greatly after day 20, indicating tidal mixing over large distances within the study area. Offshore movement was associated with seasonal warming, with alewives moving down the spatial temperature gradient and into deeper waters. Offshore, larger tidal displacements widely dispersed tagged alewives through Minas Basin and to Minas Passage. During transit of Gaspereau River, 18 ± 2 alewives were lost with corroborating evidence of mortality for 4 of these. By day 20, the apparent mortality within Minas Basin was ≤ 10 alewives. Individual alewives were observed to make many transits through Minas Passage during their migration, where they may become exposed to in-stream tidal turbines. [ABSTRACT FROM AUTHOR]

Anadromous alewives (Alosa pseudoharengus) are abundant in the Canadian Maritimes, where they support lucrative commercial fisheries. Little is known about their coastal movement, and their potential to interact with anthropogenic structures. Acoustic telemetry can provide detailed information on the spatiotemporal distribution and survival of fishes in coastal areas, using information transmitted from tagged fishes and recorded by moored receivers. However, few acoustic telemetry studies have been performed on clupeids as they are extremely sensitive to handling, and are often compromised by surgical tag implantation. This research assesses the feasibility of a surgical tagging protocol using novel High Residency acoustic tags in alewives, and establishes a baseline of short-term tagging effects. Alewives from the Gaspereau River population were tagged between 2018 (n = 29) and 2019 (n = 96) with non-transmitting models of Vemco/Innovasea V5 HR tags. Tagging effects were evaluated based on recovery rate, reflex impairment, and necropsy-based health assessments. Alewives responded well to tagging, with low mortality (3%) and no observed instances of tag shedding 72 hours post-surgery. The use of sutures to close the incision site had no effect on recovery times. Water temperature and spawning condition had the greatest effect on the behavioural response of fish to tagging. Our findings suggest that, with proper handling and smaller acoustic tags, telemetry studies on alewives are feasible. [ABSTRACT FROM AUTHOR]

To effectively protect at‐risk sharks, resource managers and conservation practitioners must have a good understanding of how fisheries removals contribute to changes in abundance and how regulatory restrictions may impact a population trajectory. This means they need to know the number of animals being removed from a population and whether a given number of removals will lead to population increases or declines. For white shark (Carcharodon carcharias), theoretical quantities like the intrinsic rate of population increase or rebound potential (ability to increase in size following decline) are difficult to conceptualize in terms of real‐world abundance changes, which limits our ability to answer practical management questions. To address this shortfall, we designed a simulation model to evaluate how our understanding of longevity and life history variability of white shark affects our understanding of population trends in the Northwest Atlantic. Then, we quantified the magnitude of removals that could have caused historical population declines, compared these to biologically based reference points, and explored the removal scenarios which would result in population increase. Our results suggest that removals on the order of 100s of juveniles per year could have resulted in population‐level declines in excess of 60% during the 1970s and 1980s. Conservation actions implemented since the 1990s would have needed to be nearly 100% effective at preventing fishing mortality in order for the population to double in abundance over the last 30 years. Total removals from all fleets needed to be exceptionally small to keep them below biological reference points for white shark in the Northwest Atlantic. The population's inherent vulnerability to fishing pressure reaffirms the need for restrictive national and international conservation measures, even under a situation of abundance increase. [ABSTRACT FROM AUTHOR]

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Describing how population-level survival rates are influenced by environmental change becomes necessary during recovery planning to identify threats that should be the focus for future remediation efforts. However, the ways in which data are analyzed have the potential to change our ecological understanding and thus subsequent recommendations for remedial actions to address threats. In regression, distributional assumptions underlying short time series of survival estimates cannot be investigated a priori and data likely contain points that do not follow the general trend (outliers) as well as contain additional variation relative to an assumed distribution (overdispersion). Using juvenile survival data from three endangered Atlantic salmon Salmo salar L. populations in response to hydrological variation, four distributions for the response were compared using lognormal and generalized linear models ( GLM). The influence of outliers as well as overdispersion was investigated by comparing conclusions from robust regressions with these lognormal models and GLMs. The analyses strongly supported the use of a lognormal distribution for survival estimates (i.e., modeling the instantaneous rate of mortality as the response) and would have led to ambiguity in the identification of significant hydrological predictors as well as low overall confidence in the predicted relationships if only GLMs had been considered. However, using robust regression to evaluate the effect of additional variation and outliers in the data relative to regression assumptions resulted in a better understanding of relationships between hydrological variables and survival that could be used for population-specific recovery planning. This manuscript highlights how a systematic analysis that explicitly considers what monitoring data represent and where variation is likely to come from is required in order to draw meaningful conclusions when analyzing changes in survival relative to environmental variation to aid in recovery planning. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Fisheries & Aquatic Sciences is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The eastern Cape Breton (ECB) designable unit (DU) of Atlantic SalmonSalmo salarcomprises populations in 46 or more rivers in the eastern portion of Cape Breton Island, Nova Scotia, Canada. In 2010, the Committee on the Status of Endangered Wildlife in Canada classified the ECB DU as endangered. In support of recovery planning processes, we developed an integrated, statistical, life history-based model for evaluating the dynamics of populations belonging to this DU. Using maximum likelihood, the model was fitted to recreational fishery catch and effort data, fish counts by divers, intermittent mark–recapture data, and sparse age composition data for two populations in the DU. The model output included estimates of maximum lifetime reproductive rate () and equilibrium population size—parameters that are important for determining extinction risk. Thefor the Middle River population (2.82 spawners/spawner) was double that of the Baddeck River population (1.39 spawners/spawner). Thesevalues would be considered low for Atlantic Salmon populations in general but are higher than those of populations in a neighboring endangered DU to the south. Slightly negative trends in recruitment deviates may indicate declining productivity in the two ECB populations; based on equilibrium analyses, neither population is expected to achieve the proposed recovery targets without an increase in productivity, survival, or both. Atlantic Salmon populations and habitat characteristics in ECB exhibit considerable diversity. Therefore, the dynamics of the Middle River and Baddeck River populations are unlikely to be representative of all populations in the ECB DU. Based on recent trends in recreational fishery catches, these two populations are likely among the healthier populations within the DU. Received July 8, 2014; accepted December 17, 2014 [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Fisheries & Aquatic Sciences is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Fisheries & Aquatic Sciences is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Recovery planning for populations in decline requires a thorough understanding of how life history characteristics, environmental conditions, and human activities interact to determine how abundance changes through time. In a detailed case study of the declining population of Atlantic salmon Salmo salar in the Tobique River, New Brunswick, we demonstrate an equilibrium modeling approach to analyzing the dynamics of the population so as to identify stressors and predict the population-level response to potential recovery actions. Parameter values for the equilibrium analysis were obtained by fitting a life history model to population-specific data, including annual estimates of juvenile density and egg deposition as well as the number and age composition of emigrating smolts. Two unique aspects of the statistical analysis--standardization of the electrofishing data using a generalized linear model and scaling of the juvenile density estimates to total abundance using a catchability coefficient--significantly improved model fits and resulted in parameter estimates that were biologically realistic. The subsequent equilibrium analysis was used to evaluate how population size was expected to change in response to recovery actions focused on fish passage, marine survival, and freshwater production. Recovery actions focused only on freshwater habitat or fish passage were not sufficient to produce an equilibrium population size greater than zero; however, either factor could limit the effectiveness of other recovery actions if not included in the recovery plan. The case study highlights the complex dynamics that can limit population growth, illustrates the need to consider the full life cycle of a species as part of the recovery planning process, and shows that responses to multiple threats may be required to bring about recovery. [ABSTRACT FROM AUTHOR]

Hubley, P. B., Amiro, P. G., Gibson, A. J. F., Lacroix, G. L., and Redden, A. M. 2008. Survival and behaviour of migrating Atlantic salmon (Salmo salar L.) kelts in river, estuarine, and coastal habitat. – ICES Journal of Marine Science, 65: 1626–1634.The downstream migration of 30 Atlantic salmon (Salmo salar) kelts tagged with acoustic transmitters was monitored using 26 underwater receivers at eight locations from April to October 2006 in the LaHave River and Estuary. In all, 27 tags were detected as they left the coastal environment by the middle of May, 5 weeks after release, indicating a possible 90% kelt survival to coastal departure. Two missing tags and one dropped tag were assumed to be attributable to natural mortality in the estuary. Migration time from release to the outermost coastal receivers 24 km below the tide limit took an average of 14 d, but varied from 3 to 32 d. Some 40% of the kelts lingered and were active in the lower estuary. Five kelts monitored with depth transmitters migrated mostly at the surface in all habitats, with occasional brief descent to the bottom. A consecutive spawning salmon returned after 79 d outside the outermost array. The low rate of returns is consistent with the historical repeat spawning schedule for this river, and more precisely documents the temporal and spatial habitat use of migrating kelts. [ABSTRACT FROM PUBLISHER]

Copyright of Canadian Journal of Fisheries & Aquatic Sciences is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Poecilogony is the production of more than one type of young within a single species of marine invertebrate. We chose a poecilogonous polychaete to investigate potential differences in morphogenesis among offspring that are polymorphic in dispersal potentials (planktonic, benthic) and trophic modes (planktotrophy, adelphophagy). Differences in morphogenesis occur and are strongly influenced by maternal type. Females that provide extra-embryonic nutrition (as nurse eggs; type III females) also produce offspring with an accelerated onset of juvenile traits, relative to planktotrophic offspring of females that do not provide extra-embryonic nutrition (type I females). Thus, progeny of some females appear morphologically preadapted for a benthic lifestyle. Surprisingly, differences in phenotype among offspring do not parallel offspring ecotype, as offspring with early onset of juvenile traits (III) are ecologically bimodal. Some Type III offspring eat the nurse eggs (adelphophagy), have accelerated development, and hatch as benthic juveniles. In contrast, their siblings hatch as small, planktotrophic, dispersive larvae that are morphologically similar to their type III siblings, but ecologically similar to Type I planktotrophic larvae. We propose that poecilogony evolved through sequence heterochrony in morphogenesis with accelerated onset of juvenile traits in type III offspring. In addition, we suggest that heterochrony in life-history events (hatching, metamorphosis) also occurs, thereby generating offspring that are dimorphic in both phenotype and ecotype. Over time, selection acting on different levels of ontogeny (morphogenesis vs. dispersal) may balance this polymorphism and allow poecilogony to persist. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Fisheries & Aquatic Sciences is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

We present a method that allows separation of fish mortality caused by handling and capture techniques from that caused by passage through a turbine. Fish that are naturally entrained into the turbine tube are captured with nets deployed in the turbine tailrace for varying lengths of time. The live or dead status of captured fish is modeled as a binomial response that is a function of the duration of net deployment. Within this model, the intercept is an estimate of the mortality of fish that have spent zero time in the net. For species that do not suffer high mortality from other components of the capture process (such as removal from the net), this intercept may be interpreted as an estimate of turbine mortality. If mortality from other components is high, the intercept cannot be interpreted as turbine mortality without correction for mortality from the other sources. We suggest a modification to the model that allows estimation of mortality from these components. We demonstrate the method with data for 12 species of fish captured at the Annapolis Tidal Generating Station, Nova Scotia, Canada. Acute turbine mortality estimates ranged from 0.0% for sea lamprey to 23.4% for American shad . [ABSTRACT FROM AUTHOR]

Provides information on the capture of several rare species of fishes at a hydroelectric generating station, Annapolis Royal, in the Annapolis Basin in Nova Scotia during the fall of 1999. Meek's halfbeak, hyporhampus meeki; Flying Gurnard, dactylopterus volitans; Bluefish, pomatomus saltatrix; Fourbeard rockling, enchelyopus cimbrius.