Sunday, February 12, 2012

Updates to fish reproductive biology

In the Spring of 2011, the American Fisheries Society's new journal, Marine and Coastal Fisheries: Dynamics, Management, and Ecosystem Science, published a special section on Fisheries Reproductive Biology.  Much of the initial work for these articles took place at the Fourth Workshop on Gonadal Histology, held in Spain in 2009. I would like to highlight three articles in this special section that I have found informative and recommend to others who are in need of a quick update on the state of reproductive biology in fisheries work.

Histological sections are increasingly common in reproductive studies as they
have repeatedly been demonstrated to produce the highest quality data.

A Standardized Terminology for Describing Reproductive Development in Fishes
(Brown-Peterson et al. 2011)

In this article, Brown-Peterson and co-authors tackle the issue of reproductive terminology. As you might imagine, a lot of independent investigators have come up with variations on terms used to describe aspects of reproduction. Due to the nature of the problem—reproduction takes place in a continuous, often overlapping nature while sampling tries to discretize information—there exist different terms for the same phase or concept and similar terms for different phases and concepts. While the nature of the problem may not be resolved, Brown-Peterson and five co-authors outline several "milestones" used to define terms and phases that are universal to all fish species. Full of clear conceptual diagrams and excellent histological images, skip to Tables 2 and 4 for the updated terms.
Table 2 provides some updated terminology.

Reproductive Timing in Marine Fishes: Variability, Temporal Scales, and Methods 
(Lowerre-Barbieri et al. 2011)

In a continued effort to clarify the interpretation of reproductive themes, Lowerre-Barbieri and co-authors  present an overview on one of the most variable (and interesting!) aspects of reproductive biology—timing.  The authors address all aspects of timing, from individual oocyte maturation to patterns of lifetime maturation and the grouping of similar timing into reproductive strategies. They recommend first identifying the temporal scale of interest: lifetime, annual, intra-seasonal, and diel. Within these classifications, each layer has its own patterns and inconsistencies and the article does a good job at summarizing them. Although recent work has increased the focus on the timing of reproduction, the authors still identify this as an upcoming area of fisheries biology—both in the sense that basic reproductive parameters still need to be investigated, all the way to how temporal variability and scales can impact a fishery.

Emerging Issues and Methodological Advances in Fisheries Reproductive Biology 
(Lowerre-Barbieri et al. 2011)

This paper is perhaps the broadest in its discussion of reproductive themes. After the calls for increased reproductive information to be included in assessments, the authors suggest that new ways of thinking about reproductive data may improve fisheries management.  For example, estimates such as percent mature and egg production are often used to get at spawning stock biomass (SSB), but recent work has clearly demonstrated that older and larger females contribute disproportionally to offspring production. Total egg production (TEP) is provided as a possible replacement for SSB, and in general, the paper advocates measures of reproductive potential and stock resilience in addition to the tradition abundance estimates. Finally, the authors address concerns of fisheries-induced evolution as these changes are often tightly linked to harvest-induced changes to reproductive strategies.
Over the last 10 years, reproductive studies have increased significantly.

Fisheries researchers who work with reproductive themes are likely familiar with these recent papers, but these (and other papers in the special section) are excellent ways to stay up to speed with some of the current approaches in fish reproduction. One additional bonus to these papers is that Marine and Coastal Fisheries is an open-access journal, meaning anyone can get copies of these articles: Marine and Coastal Fisheries Journal

Steve Midway

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