The application of molecular systematics to the anisakid nematodes of the genera Anisakis, Pseudoterranova and Contracaecum, parasites of aquatic organisms, over the last two decades, has advanced the understanding of their systematics, taxonomy, ecology and phylogeny substantially Here the results of this effort on this group of species from the early genetic works to the current status of their revised taxonomy, ecology and evolutionary aspects are reviewed for each of three parasitic groups It has been shown that many anisakid morphospecies of Anisakis, Contracaecum and Pseudoterranova include a certain number of sibling species Molecular genetic markers provided a rapid, precise means to screen and identify several species that serve as definitive and intermediate and or/paratenic hosts of the so far genetically characterized species Patterns of differential distribution of anisakid nematodes in various definitive and intermediate hosts are presented Differences in the life history of related species can be due both to differential host-parasite co-adaptation and co-evolution, and/or to interspecific competition, that can reduce the range of potential hosts in sympatric conditions Phylogenetic hypotheses attempted for anisakid nematodes and the possible evolutionary scenarios that have been proposed inferred from molecular data, also with respect to the phylogeny of their hosts are presented for the parasite-host associations Anisakis-cetaceans and Contracaecum-pinnipeds, showing that codivergence and host-switching events could have accompanied the evolution of these groups of parasites Finally, examples in which anisakid nematodes recognized genetically at the species level in definitive and intermediate/paratenic hosts from various geographical areas of the Boreal and Austral regions and their infection levels have been used as biological indicators of fish stocks and food-web integrity in areas at high versus low levels of habitat disturbance (pollution, overfishing, by-catch) are presented

Advances and trends in the molecular systematics of anisakid nematodes, with implications for their evolutionary ecology and host-parasite co-evolutionary processes.

Freshwater fish move vertically and horizontally through the aquatic landscape for a variety of reasons, such as to find and exploit patchy resources or to locate essential habitats (e.g., for spawning). Inherent challenges exist with the assessment of fish populations because they are moving targets. We submit that quantifying and describing the spatial ecology of fish and their habitat is an important component of freshwater fishery assessment and management. With a growing number of tools available for studying the spatial ecology of fishes (e.g., telemetry, population genetics, hydroacoustics, otolith microchemistry, stable isotope analysis), new knowledge can now be generated and incorporated into biological assessment and fishery management. For example, knowing when, where, and how to deploy assessment gears is essential to inform, refine, or calibrate assessment protocols. Such information is also useful for quantifying or avoiding bycatch of imperiled species. Knowledge of habitat connectivity and usage can identify critically important migration corridors and habitats and can be used to improve our understanding of variables that influence spatial structuring of fish populations. Similarly, demographic processes are partly driven by the behavior of fish and mediated by environmental drivers. Information on these processes is critical to the development and application of realistic population dynamics models. Collectively, biological assessment, when informed by knowledge of spatial ecology, can provide managers with the ability to understand how and when fish and their habitats may be exposed to different threats. Naturally, this knowledge helps to better evaluate or develop strategies to protect the long-term viability of fishery production. Failure to understand the spatial ecology of fishes and to incorporate spatiotemporal data can bias population assessments and forecasts and potentially lead to ineffective or counterproductive management actions.

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A moving target—incorporating knowledge of the spatial ecology of fish into the assessment and management of freshwater fish populations

How does fishing alter marine populations and ecosystems sensitivity to climate

Geographic variation in morphometry has been used todiscriminate local forms of fish for over a century. The historical development of stock identificationmethods has paralleled the advancement of morphometrictechniques. The earliest analyses of morphometricvariables for stock identification were univariatecomparisons, but were soon followed by bivariateanalyses of relative growth to detect ontogeneticchanges and geographic variation among fishstocks. As the field of multivariatemorphometrics flourished, a suite of multivariatemethods was applied to quantify variation in growthand form among stocks. More recent advances have beenfacilitated by image processing techniques, morecomprehensive and precise data collection, moreefficient quantification of shape, and new analyticaltools. Many benchmark case studies and critiquesoffer guidelines for sampling morphometrics andinterpreting multivariate analyses for exploratorystock identification, stock discrimination, and stockdelineation. As examples of morphometric stockidentification based on life history differences,allometric patterns of crustacean secondary sexcharacters have been used to detect geographicvariation in size at maturity, and morphometriccorrelates to smoltification have been used todiscriminate salmon from different rivers. Morphometric analysis provides a powerful complementto genetic and environmental stock identificationapproaches. The challenge for the future ofmorphometric stock identification is to develop aconsensus on biological interpretations of geometricanalyses, similar to the conventional interpretationsof size and shape from traditional multivariatemorphometrics.

Advances in morphometric identification of fishery stocks

Evidence accumulated over the last decade indicates that reproductive potential of marine fish stocks is not correctly represented by spawning stock biomass. Fundamental variables that affect reproductive potential of fish stocks (i.e. proportion mature at age, fecundity, and offspring size and viability) have found to vary with age, size, and condition of spawning fish, and/or spawn- ing experience. Modeling initiatives that attempt to describe reproductive potential by incorporating all available information on reproductive variables require extensive, high quality data of a temporal and spatial origin. In this study, we explored the influence of female age, size, and condition on sev- eral reproductive variables for the cod Gadus morhua, including maturity, fecundity, egg density and size, and larval size and growth. In addition, we described the potential for annual variation in these relationships to increase our knowledge of temporal stability for fundamental variables that influence reproductive potential.

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Essential relationships incorporating the influence of age, size and condition on variables required for estimation of reproductive potential in Atlantic cod Gadus morhua

An holistic approach to fish stock identification

Stock identification and its role in stock assessment and fisheries management: an overview

Otolith shape analysis was examined to determine its utility for stock identification of haddock Melanogrammus aeglefinus on Georges Bank. Otolith samples were collected from the Northeast Peak (eastern Georges Bank) and the Great South Channel (western Georges Bank) spawning components to examine stock continuity across Georges Bank. Otolith shape was described using 20 Fourier harmonics, four morphometric characteristics (area, length, width, and perimeter), and two shape indices (circularity and rectangularity). Potential confounding sources of variation (fish length, otolith position, age-group, and year-class) were examined and accounted for in the analyses before interpretation of spatial/stock differences. Significant age-specific differences in otolith shape between eastern and western Georges Bank haddock indicated stock separation across the Bank. Classification success for each spawning component ranged from 63 to 80% across age-groups and appeared to depend on growth rate differences....

Stock Identification of Haddock Melanogrammus aeglefinus on Georges Bank Based on Otolith Shape Analysis

The role of life history parameters as indicators of stock structure

Haddock, Melanogrammus aeglefinus, is a principal commercial species distributed throughout the northwest
Atlantic Ocean, with major aggregations occurring on Georges Bank and on the Scotian Shelf. This review examines all available information on stock structure of haddock to evaluate the suitability of current stock units and to investigate areas that require further research. Combined information from tag-recapture, demographic, recruitment,
meristic, parasitic, and genetic studies provide evidence for the identification of haddock stocks, with major population divisions occurring between New England, Nova Scotia, and Newfoundland waters. Within each of these major divisions a number of discrete stocks appear to exist, although uncertainty remains in the amount of separation found within each region. Research utilizing more recent stock identification techniques should refine and improve
our understanding of haddock stock structure in the northwest Atlantic.

Gavin A. Begg

Papers

An holistic approach to fish stock identification

Stock identification and its role in stock assessment and fisheries management: an overview

Stock Identification of Haddock Melanogrammus aeglefinus on Georges Bank Based on Otolith Shape Analysis

The role of life history parameters as indicators of stock structure

A Review of Stock Identification of Haddock, Melanogrammus aeglefinus, in the Northwest Atlantic Ocean