Sexual Variation in Fisheries Research and Management: When Does Sex Matter?

Abstract

In fish, sex determination is a plastic process regulated by a relatively small number of genes that, in turn, leads to a cascade of organism level effects. In other animal taxa, intersexual variation is widespread and has implications in the realms of morphology, behavior, physiology, and bioenergetics. Although relatively well documented in the literature focusing on mammals, birds, and reptiles, the degree to which sex-specific variation is considered is unknown in fish and fisheries research. We examined the scientific literature to evaluate the important sex-related differences in fish and highlighted why some of these differences are of great biological consequence. Sex-specific differences in morphology included sexual size dimorphism, external traits such as coloration, and internal anatomy such as neuron structure. Behavioral differences between the sexes are often linked to reproduction, but there are some documented differences (i.e., variation in aggression and predator avoidance) that are independent of the reproductive period. The potential for sex-related physiological differences are relatively unexplored for fish, although there is strong evidence for disparity in hormone regulation, stress, and immune responses between the sexes. Sex-related variation is also poorly examined in the field of bioenergetics despite the fact that differences in energy requirements and expenditure should and do vary between the sexes. A quantitative literature review of several prominent fisheries journals revealed that sex is often overlooked in fish and fisheries research (between 15 and 44% of articles), which may impair the ability of researchers to detect biologically relevant differences, which in turn can greatly affect management decisions. Although there has been a growing recognition that intra-specific variation (at the population level) is important in fisheries management and research, there is also a need to consider that intersexual diversity exists and is important to understand, conserve, and manage fish and fisheries resources.

Sex-specific differences in cardiac control and hematology of sockeye salmon (Oncorhynchus nerka) approaching their spawning grounds

“…Sex is an often neglected variable when analyzing cardiovascular data from nonmammalian vertebrates (9,34). To the best of our knowledge, this is the first study to investigate sex-specific differences in autonomic nervous control of cardiac function in any species of fish.…”

“…Although it is evident that cardiac function, and thus resilience to environmental perturbations, can differ considerably among species and even between strains within a species (e.g., Ref. 30), few studies have examined for intraspecific and sex-related differences (9,34).…”

Advancing the surgical implantation of electronic tags in fish: a gap analysis and research agenda based on a review of trends in intracoelomic tagging effects studies

“…Aside from fish size and life-stage (juvenile versus adult), very few studies have examined how intrinsic biotic factors influence surgical outcome. For example, despite the fact that male and female fish often vary with respect to their life-history characteristics, behaviour and physiology (Hanson et al 2008a), sex or stage of sexual development (aside from juvenile versus adult; see above) is rarely used as a factor in analyses or explicitly contrasted. Baras and Westerloppe (1999) were one of the few to include sex and state of reproductive development in their analysis and found no significant effect of those factors.…”

Sex Differences in Residency of Adult Spotted Seatrout in a Louisiana Estuary

“…Generally speaking, sex-specific movements in coastal fishes are understudied, and for those species able to be sexed, a great deal may be learned if sex is explicitly taken into account in studies of movement and behavior. For instance, as Hanson et al (2008) noted, part of the variation in movements and behavior typically ascribed to differences among individuals or considered "noise" might be related to sex. As demonstrated in this study, consideration of sex-specific movements can lead to unexpected results and enhance our understanding of the basic ecology of coastal fishes and improve the management of important fishery resources.…”