GLORIA

GEOMAR Library Ocean Research Information Access

X

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • Canadian Science Publishing  (14)
  • Trenkel, Verena  (14)
  • 1
    Online Resource
    Online Resource
    A comparison of hierarchical models for relative catch efficiency based on paired-gear data for US Northwest Atlantic fish stocks
    Canadian Science Publishing ; 2013
    In:  Canadian Journal of Fisheries and Aquatic Sciences Vol. 70, No. 9 ( 2013-09), p. 1306-1316
    Details
    In: Canadian Journal of Fisheries and Aquatic Sciences, Canadian Science Publishing, Vol. 70, No. 9 ( 2013-09), p. 1306-1316
    Abstract: Selectivity and catch comparison studies are important for surveys that use two or more gears to collect relative abundance information. Prevailing model-based analytical methods for studies using a paired-gear design assume a binomial model for the data from each pair of gear sets. Important generalizations include nonparametric smooth size effects and normal random pair and size effects, but current methods for fitting models that account for random smooth size effects are restrictive, and observations within pairs may exhibit extra-binomial variation. I propose a hierarchical model that accounts for random smooth size effects among pairs and extra-binomial variation within pairs with a conditional beta-binomial distribution. I compared relative performance of models with different conditional distribution and random effects assumptions fit to data on 16 species from an experiment carried out in the US Northwest Atlantic Ocean comparing a new and a retiring vessel. For more than half of the species, conditional beta-binomial models performed better than binomial models, and accounting for random variation among pairs in the relative efficiency was important for all species.
    Type of Medium: Online Resource
    ISSN: 0706-652X , 1205-7533
    URL: Article
    DOI: 10.1139/cjfas-2013-0136
    Language: English
    Publisher: Canadian Science Publishing
    Publication Date: 2013
    detail.hit.zdb_id: 7966-2
    detail.hit.zdb_id: 1473089-3
    SSG: 21,3
    SSG: 12
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
  • 2
    Online Resource
    Online Resource
    Optimal management of recreational fisheries in the presence of hooking mortality and noncompliance — predictions from a bioeconomic model incorporating a mechanistic model of angler behavior
    Canadian Science Publishing ; 2015
    In:  Canadian Journal of Fisheries and Aquatic Sciences Vol. 72, No. 1 ( 2015-01), p. 37-53
    Details
    In: Canadian Journal of Fisheries and Aquatic Sciences, Canadian Science Publishing, Vol. 72, No. 1 ( 2015-01), p. 37-53
    Abstract: Using a bioeconomic model, we systematically investigated how hooking mortality and regulatory noncompliance influenced management outcomes across a range of freshwater fish species exploited by diverse angler populations. The model integrated an empirically based submodel describing the behaviour of three angler types with an age-structured fish population submodel calibrated to five life-history types (LHTs). Increased hooking mortality generally undermined regulation effectiveness, decreased socially optimal input (license numbers) and output regulations (minimum-size limits), and eroded the social welfare anglers derived from the fishery. However, the results strongly varied with LHT and angler type. Noncompliance had an isolated effect, primarily affecting fish species with low compensatory reserves when hooking mortality was low. However, in the absence of regulatory constraints on effort, noncompliance facilitated recruitment overfishing and increased the minimum-size limit required to avoid it. Despite added mortality from hooking and noncompliance, the strong dependence of angler utility on catch rates usually meant socially optimal management safeguarded biological sustainability. Yet, ignoring hooking mortality and noncompliance when predicting optimal regulations often led to population collapse. To conclude, models designed to derive recommendations for recreational fisheries management must consider both hooking mortality and noncompliance. Otherwise, dissatisfied anglers or biologically overfished stocks are possible.
    Type of Medium: Online Resource
    ISSN: 0706-652X , 1205-7533
    URL: Article
    DOI: 10.1139/cjfas-2013-0650
    Language: English
    Publisher: Canadian Science Publishing
    Publication Date: 2015
    detail.hit.zdb_id: 7966-2
    detail.hit.zdb_id: 1473089-3
    SSG: 21,3
    SSG: 12
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
  • 3
    Online Resource
    Online Resource
    A photographic method for lobster morphometry aimed at site discrimination
    Canadian Science Publishing ; 2013
    In:  Canadian Journal of Fisheries and Aquatic Sciences Vol. 70, No. 11 ( 2013-11), p. 1658-1665
    Details
    In: Canadian Journal of Fisheries and Aquatic Sciences, Canadian Science Publishing, Vol. 70, No. 11 ( 2013-11), p. 1658-1665
    Abstract: Current data suggest that lobster (Homarus americanus) populations are less homogenous than once believed. In an effort to better discriminate morphologically among lobsters from different sites, we developed a photographic method using ImageJ and compared it with commonly used “hand” measurements. We standardized the measuring process using a strap-down board for both dorsal and ventral photographs with a camera mounted at a fixed position above the lobster. Discriminant analysis showed that both hand and photographic methods were useful in discriminating lobsters — both males and females — from three different sites. Additionally, the photographic method improved reproducibility and resolution, it reduced measurement time at the dock, and it created a permanent record for later verification, additional statistical analyses, and observer training.
    Type of Medium: Online Resource
    ISSN: 0706-652X , 1205-7533
    URL: Article
    DOI: 10.1139/cjfas-2013-0103
    Language: English
    Publisher: Canadian Science Publishing
    Publication Date: 2013
    detail.hit.zdb_id: 7966-2
    detail.hit.zdb_id: 1473089-3
    SSG: 21,3
    SSG: 12
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
  • 4
    Online Resource
    Online Resource
    Tracking the fidelity of Atlantic bluefin tuna released in Canadian waters to the Gulf of Mexico spawning grounds
    Canadian Science Publishing ; 2015
    In:  Canadian Journal of Fisheries and Aquatic Sciences Vol. 72, No. 11 ( 2015-11), p. 1700-1717
    Details
    In: Canadian Journal of Fisheries and Aquatic Sciences, Canadian Science Publishing, Vol. 72, No. 11 ( 2015-11), p. 1700-1717
    Abstract: The objective of this study was to advance the use of pop-up satellite archival tags to track the migrations of Atlantic bluefin tuna (Thunnus thynnus) to their spawning grounds. Deployment of tags occurred in the Gulf of St. Lawrence, Canada, during fall months from 2007 to 2013. Pop-up satellite archival tags (n = 135) were attached to 125 Atlantic bluefin tuna (curved fork length (CFL) = 268 ± 20 cm (mean ± SD)) with the objective of keeping tags on until visitation to a spawning area or longer. A dataset of 18 800 days was acquired, which included 5800 days of time-series data from 19 recovered satellite tags. Many Atlantic bluefin tuna visited the Gulf of Mexico spawning grounds (74%), the mean size of which was 275 ± 14 cm (CFL ± SD, n = 49), with a measured CFL of 243 to 302 cm. These fish had a mean entry date into the Gulf of Mexico of 14 January ± 42 days (SD). The mean residency period for fish that had tracks with entrance and exit from the Gulf of Mexico was 123 ± 49 days (SD) (n = 22). Atlantic bluefin tuna that moved into the Gulf of Mexico during the spawning season remained west of the 45°W meridian for the duration of the track. Electronic tagging datasets from two fish were obtained before, during, and after the Deepwater Horizon oil spill. Both fish utilized habitat in the vicinity of the Macondo Well on 20 April 2010 when the Deepwater Horizon oil drilling rig accident occurred. Spawning hotspots are identified in the Gulf of Mexico using kernel density analyses and compared with the newly established closed areas.
    Type of Medium: Online Resource
    ISSN: 0706-652X , 1205-7533
    URL: Article
    DOI: 10.1139/cjfas-2015-0110
    Language: English
    Publisher: Canadian Science Publishing
    Publication Date: 2015
    detail.hit.zdb_id: 7966-2
    detail.hit.zdb_id: 1473089-3
    SSG: 21,3
    SSG: 12
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
  • 5
    Online Resource
    Online Resource
    Using a state-space population model to detect age-dependent species interactions
    Canadian Science Publishing ; 2016
    In:  Canadian Journal of Fisheries and Aquatic Sciences Vol. 73, No. 5 ( 2016-05), p. 811-818
    Details
    In: Canadian Journal of Fisheries and Aquatic Sciences, Canadian Science Publishing, Vol. 73, No. 5 ( 2016-05), p. 811-818
    Abstract: Models that incorporate species interactions and their effects on the dynamics of commercially important fish stocks are needed to better understand the importance of ecological interactions and to facilitate sustainable fisheries. We developed a dynamic age-structured population model for the Northeast Arctic stock of Atlantic haddock (Melanogrammus aeglefinus) based on scientific survey and commercial landings data. Our goal was to investigate climate effects and ecological interactions within the haddock food web. A Bayesian state-space framework was used to separate information from ecological noise and observation error. Our results indicate significant impacts of species interactions on haddock dynamics. Haddock survival was associated with biomass indices of cod (Gadus morhua) (negative effect) and capelin (Mallotus villosus) (positive effect). The latter may reflect lower predation by predators such as marine mammals at high capelin biomass. We further detect weak density dependence in the survival of young haddock and a convex relationship between haddock abundance and the scientific survey indices. Our findings highlight the importance of considering natural resources as part of an ecosystem with its diverse interactions both within and between species. This study shows that it is possible to detect ecological interactions with a population model based on noisy data.
    Type of Medium: Online Resource
    ISSN: 0706-652X , 1205-7533
    URL: Article
    DOI: 10.1139/cjfas-2015-0004
    Language: English
    Publisher: Canadian Science Publishing
    Publication Date: 2016
    detail.hit.zdb_id: 7966-2
    detail.hit.zdb_id: 1473089-3
    SSG: 21,3
    SSG: 12
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
  • 6
    Online Resource
    Online Resource
    Examining the utility of alternative video monitoring metrics for indexing reef fish abundance
    Canadian Science Publishing ; 2014
    In:  Canadian Journal of Fisheries and Aquatic Sciences Vol. 71, No. 3 ( 2014-03), p. 464-471
    Details
    In: Canadian Journal of Fisheries and Aquatic Sciences, Canadian Science Publishing, Vol. 71, No. 3 ( 2014-03), p. 464-471
    Abstract: Underwater video has become an important tool for monitoring reef fish populations worldwide because it is nonextractive and not strongly selective. A variety of approaches have been developed to enumerate fish on videos, but to our knowledge these metrics have not been tested to determine if they are proportional to true abundance. We compared the most commonly used metric, MaxN (i.e., the maximum number of fish in a single frame during the viewing interval), to a newly developed metric, MeanCount (i.e., the mean number of fish observed in a series of snapshots over a viewing interval), using simulations, a laboratory experiment, and an empirical study. MaxN was nonlinearly related to true abundance using all three approaches, providing increasingly dampened estimates of abundance with increasing true abundance (i.e., hyperstability). Therefore, MaxN may result in positively biased indices of abundance for declining fish stocks or negatively biased abundance indices when fish stocks are increasing. Alternatively, MeanCount was generally linearly related to true abundance and its variability was similar to MaxN, suggesting that MeanCount can be useful for indexing abundance of fish in underwater video surveys.
    Type of Medium: Online Resource
    ISSN: 0706-652X , 1205-7533
    URL: Article
    DOI: 10.1139/cjfas-2013-0086
    Language: English
    Publisher: Canadian Science Publishing
    Publication Date: 2014
    detail.hit.zdb_id: 7966-2
    detail.hit.zdb_id: 1473089-3
    SSG: 21,3
    SSG: 12
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
  • 7
    Online Resource
    Online Resource
    Bayesian posterior prediction of the patchy spatial distributions of small pelagic fish in regions of suitable habitat
    Canadian Science Publishing ; 2015
    In:  Canadian Journal of Fisheries and Aquatic Sciences Vol. 72, No. 2 ( 2015-02), p. 290-303
    Details
    In: Canadian Journal of Fisheries and Aquatic Sciences, Canadian Science Publishing, Vol. 72, No. 2 ( 2015-02), p. 290-303
    Abstract: Small pelagic fish aggregate within areas of suitable habitat to form patchy distributions with localized peaks in abundance. This presents challenges for geostatistical methods designed to investigate the processes underpinning the spatial distribution of stocks and simulate distributions for further analysis. In two-stage models, presence–absence is treated as separable and independent from the process explaining nonzero densities. This is appropriate where gaps in the distribution are attributable to one process and conditional abundance to another, but less so where patchiness is attributable primarily to the strong schooling tendencies of small pelagic fish within suitable habitat. We therefore developed a new modelling framework based on a truncated Gaussian random field (GRF) within a Bayesian framework. We evaluated this method using simulated test data and then applied it to acoustic survey data for Peruvian anchoveta (Engraulis ringens). We assessed the method’s performance in terms of posterior densities of spatial parameters, and the density distribution, spatial pattern, and overall spatial distribution of posterior predictions. We conclude that Bayesian posterior prediction based on a truncated GRF is effective at reproducing the patchiness of the observed spatial distribution of anchoveta.
    Type of Medium: Online Resource
    ISSN: 0706-652X , 1205-7533
    URL: Article
    DOI: 10.1139/cjfas-2014-0234
    Language: English
    Publisher: Canadian Science Publishing
    Publication Date: 2015
    detail.hit.zdb_id: 7966-2
    detail.hit.zdb_id: 1473089-3
    SSG: 21,3
    SSG: 12
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
  • 8
    Online Resource
    Online Resource
    Deriving high-resolution spatiotemporal fishing effort of large-scale longline fishery from vessel monitoring system (VMS) data and validated by observer data
    Canadian Science Publishing ; 2014
    In:  Canadian Journal of Fisheries and Aquatic Sciences Vol. 71, No. 9 ( 2014-09), p. 1363-1370
    Details
    In: Canadian Journal of Fisheries and Aquatic Sciences, Canadian Science Publishing, Vol. 71, No. 9 ( 2014-09), p. 1363-1370
    Abstract: Estimating geo-referenced fishing effort is vital to develop advice for effective fisheries management. Many studies in recent decades have attempted to obtain complete, high-resolution effort data from vessel monitoring systems (VMSs). The main challenge in this regard is to develop a classification method for differentiating fishing activities (e.g., fishing days) from nonfishing activities in VMS data. This study developed a simple, novel classification criterion for a large-scale tuna longline (LTLL) fishery that has not been studied before. LTLL operations were first explored using observer data. Three approaches were designed for developing fishing-day classification criteria, using maximizing sum of sensitivity and specificity (SS) as the major performance measure and minimizing difference of SS as a reference. At least one VMS report with speed in the range of 2–5 kn (1 kn = 1.852 km·h –1 ) detected during the time-of-day period of 14:00–23:00 h was recommended as the criterion for defining a fishing day. Possible explanations for the differences between the estimated fishing days from VMS data and those reported on logbooks are discussed; most causes were related to specific features of the fishery.
    Type of Medium: Online Resource
    ISSN: 0706-652X , 1205-7533
    URL: Article
    DOI: 10.1139/cjfas-2013-0552
    Language: English
    Publisher: Canadian Science Publishing
    Publication Date: 2014
    detail.hit.zdb_id: 7966-2
    detail.hit.zdb_id: 1473089-3
    SSG: 21,3
    SSG: 12
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
  • 9
    Online Resource
    Online Resource
    New abbreviated calculation for measuring intrinsic rebound potential in exploited fish populations — example for sharks
    Canadian Science Publishing ; 2015
    In:  Canadian Journal of Fisheries and Aquatic Sciences Vol. 72, No. 5 ( 2015-05), p. 767-773
    Details
    In: Canadian Journal of Fisheries and Aquatic Sciences, Canadian Science Publishing, Vol. 72, No. 5 ( 2015-05), p. 767-773
    Abstract: Intrinsic rebound potential, the demographic measure of a fish population’s productivity that sustains a given mortality, relates to a species’ resiliency and can be useful for understanding and evaluating the status of exploited populations, especially those poorly monitored and of low productivity, like many shark populations. The rebound potential is derived from the Euler–Lotka equation and, with the dynamics kept simple, is easily calculated for a given total mortality, needing only a species’ age at maturity and its natural mortality (M). Its value can be quickly read from an isopleth diagram, whose contour pattern shows the interdependence of these two key parameters among different life histories. How the rebound potentials change as a function of age at maturity and the full range of possible M values also shows a way to estimate a species’ natural mortality bounds. Importance of the age at maturity parameter is stressed.
    Type of Medium: Online Resource
    ISSN: 0706-652X , 1205-7533
    URL: Article
    DOI: 10.1139/cjfas-2014-0360
    Language: English
    Publisher: Canadian Science Publishing
    Publication Date: 2015
    detail.hit.zdb_id: 7966-2
    detail.hit.zdb_id: 1473089-3
    SSG: 21,3
    SSG: 12
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
  • 10
    Online Resource
    Online Resource
    Modeling freshwater mussel distribution in relation to biotic and abiotic habitat variables at multiple spatial scales
    Canadian Science Publishing ; 2014
    In:  Canadian Journal of Fisheries and Aquatic Sciences Vol. 71, No. 10 ( 2014-10), p. 1483-1497
    Details
    In: Canadian Journal of Fisheries and Aquatic Sciences, Canadian Science Publishing, Vol. 71, No. 10 ( 2014-10), p. 1483-1497
    Abstract: The habitat requirements of many native freshwater mussels remain unclear despite their imperiled status and ecological importance. To explore scale-specific habitat associations in the three genera of mussels found in the western United States (Anodonta, Gonidea, and Margaritifera) we used a multiscale random forest modeling approach to assess functional habitat parameters throughout a 55 km segment of the upper Middle Fork John Day River in northeastern Oregon. We characterized mussel occurrence and density with respect to the hierarchical, hydrogeomorphic structure by sampling reaches of varying valley confinement and channel units nested within individual reaches. Each genus exhibited unique longitudinal trends and channel unit-use patterns. In particular, the large-scale longitudinal trends in Margaritifera occurrence were associated with hydrogeomorphic characteristics at the reach and channel unit scale, with Margaritifera densities peaking in narrow valley segments and in riffles and runs. At the scale of the channel unit, all mussel genera responded to variation in physical habitat characteristics, particularly those that indicated more stable parts of the channel. Our results suggest that spatial patterns in freshwater mussels are associated with the hierarchical structuring of the lotic ecosystem and may provide guidance to restoration efforts.
    Type of Medium: Online Resource
    ISSN: 0706-652X , 1205-7533
    URL: Article
    DOI: 10.1139/cjfas-2014-0110
    Language: English
    Publisher: Canadian Science Publishing
    Publication Date: 2014
    detail.hit.zdb_id: 7966-2
    detail.hit.zdb_id: 1473089-3
    SSG: 21,3
    SSG: 12
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...