Development of a Nonlethal and Minimally Invasive Protocol to Study Elasmobranch Reproduction

Bianca K Prohaska,Paul C W Tsang,William B Driggers,Eric R Hoffmayer,James A Sulikowski

doi:10.1080/19425120.2013.788590

Abstract

AbstractAn understanding of basic reproductive biology is essential for successful species‐specific management of elasmobranch fishes (sharks, skates, and rays). Such information is often gained through gross dissection or other lethal techniques, which are not appropriate for threatened and endangered species. Previous work on other vertebrates suggested that sex steroid hormones can be extracted from muscle tissues to identify reproductive status. Collecting for muscle biopsy is quick and minimally invasive and can be done without removing an animal from the water. Thus, the objective of the current study was to determine the efficacy of using muscle steroid hormones to assess the reproductive biology of elasmobranch fishes. The results suggest that concentrations of muscle progesterone, testosterone, and estradiol can be successfully quantified to study reproduction by radioimmunoassay. Additionally, there were significant correlations between the plasma and muscle estradiol concentrations in Spiny Dogfish Squalus acanthias and the progesterone, testosterone, and estradiol concentrations in Atlantic Sharpnose Sharks Rhizoprionodon terraenovae. The present investigation thus demonstrates that skeletal muscle is a nonlethally harvestable tissue that is well suited for studying the reproductive biology of elasmobranchs.Received October 12, 2012; accepted March 12, 2013

Highlights

An understanding of basic reproductive biology is essential for successful species-specific management of elasmobranch fishes
Given the lack of knowledge pertaining to the reproductive biology of elasmobranch fishes, the objectives of the present study were to determine (1) whether reproductive steroid hormones can be quantified from elasmobranch skeletal muscle tissue and (2) whether there is a relationship between the muscle and plasma concentrations of these reproductive hormones
Specimen collection.—Based on their relatively high abundance and ease of collection, the aplacental viviparous Spiny Dogfish Squalus acanthias and yolk sac placental viviparous Atlantic Sharpnose Shark Rhizoprionodon terraenovae were selected as study organisms

Summary

Introduction

An understanding of basic reproductive biology is essential for successful species-specific management of elasmobranch fishes (sharks, skates, and rays). Studying the reproductive biology of elasmobranchs entailed sacrificing a relatively large number of specimens and observing the changes in gross reproductive morphology over the reproductive cycle (e.g., Hisaw and Albert 1947; Zeiner and Wolf 1993; Walmsley-Hart et al 1999; Francis et al 2001; Ebert 2005; Ruocco et al 2006) While this approach is still currently appropriate for elasmobranchs with sustainable population sizes (Heupel and Simpfendorfer 2010), it is not suitable for many because of their relatively low or unknown species abundance (IUCN 2011; Hammerschlag and Sulikowski 2011). Plasma steroid hormone analysis is useful for studying the reproductive biology of elasmobranchs, the aforementioned constraints make it necessary for new, less invasive approaches to be developed, especially for studying vulnerable species

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