Stock Identification: Materials and Methods

Abstract

Various population parameters and physiological, behavioral, morphometric, meristic, calcareous, biochemical, and cytogenetic characters have been used to identify fish stocks. We define a stock as an intraspecific group of randomly mating individuals with temporal or spatial integrity. Each character set and the associated methodology relates to specific aspects of the stock definition. Population parameters are useful primarily for the recognition of putative stocks at the practical fisheries management level. Physiological and, to some degree, behavioral characters are used primarily to study differences in the adaptation of stocks to different environments. Behavioral characters are also important for the recognition of stocks and the study of their spatial and temporal discreteness. Morphological characters, including morphometric measurements, meristic counts, and the shape, size, and type of zonation in calcareous structures provide data that are useful for the precise description of and differentiation among stocks. Although the genetic control of this type of variation is poorly understood, multivariate methods coupled with shape analyses provide techniques that describe intraspecific subdivisions that have been found to correspond to genetic stock structure as determined by other methods. Intraspecific chromosomal variation has, on occasion, been employed for stock identification. This variation has had only limited application to the study of stocks because of complications arising from intraindividual variation and artifactual variation introduced by the methodology. Electrophoresis provides an important method for measuring the genetic discreteness of stocks and for the study of genetic relationships among stocks. Electrophoretic data have recently attained a primary position among the methods used for stock identification.Key words: stock identification, genotype, phenotype, population parameters, marking, physiological, behavioral, morphometric, meristic, calcareous, cytogenetic, and biochemical characters

Genetic and morphometric differences between yellowtail snapper (Ocyurus chrysurus, Lutjanidae) populations of the tropical West Atlantic

“…The correct stock as-sessment and identification of the species is fundamental to establish the maximum sustainable effort of a given marine resource (Ryman and Utter, 1987;Ryman, 1991). Many stock concepts can be found in the literature (Booke, 1981;Ovenden, 1990;Smith et al, 1990;Carvalho and Hauser, 1995), but one of the most accepted and used is that "a stock is an intraspecific group of randomly mating individuals with temporal and spatial integrity" (Ihssen et al, 1981) which covers most of the definitions given by other authors.…”

Marine Growth and Morphometrics for Three Populations of Atlantic Salmon from Eastern Maine, USA

“…It is unlikely that the remnant populations exist in their pure native form, but their persistence over time in their indigenous habitat suggests that important heritable adaptations probably still exist (Colligan et al 1999). Ihssen et al (1981) defined a stock as an intraspecific group of randomly mating individuals with temporal or spatial integrity. Discrete salmon stocks are maintained by natural selection and precise homing (Ricker 1972;.…”

“…However, the linkage between these subtle genetic differences and their corresponding adaptive characteristics, as expressed by morphological or behavioral differences between and among stocks, has rarely been examined for Atlantic salmon (Ihssen et al 1981;Nielsen 1998). A better understanding of what these subtle genetic differences between populations mean relative to biology is important to informed decision making.…”

“…Phenotypic variation observed between different strains of fish reared in a common environment is primarily due to heritability of genetic factors (Tave 1986). These types of tests are most effective when the populations studied have experienced extreme selection pressures or large population declines (Ihssen et al 1981), as Maine Atlantic salmon have (Colligan et al 1999).…”

Population genetic structure and body shape assessment of Pagrus pagrus (Linnaeus, 1758) (Perciformes: Sparidae) from the Buenos Aires coast of the Argentine Sea

“…In terms of conservation, an Evolutionary Significant Unit (ESU) is primarily relevant for long-term management but, in the short term, a Management Unit or "stock" is understood as groups of individuals whose level of ecological and genetic connectivity is low enough. Hence each group must be individually monitored and managed (Ihssen et al, 1981;Laikre et al, 2005;Waldman, 2005;Palsboll et al, 2007).…”