The role of early life freshwater tolerance and combined stressors in limiting freshwater colonization in Atlantic Canadian stickleback species

Abstract

<p>Atlantic Canadaian stickleback fishes (<em>Gasterosteidae</em>) differ in the salinities they inhabit; Threespine (<em>Gasterosteus aculeatus</em>) and fourspine (<em>Apeltes quadracus</em>) sticklebacks inhabit salinities from freshwater to saltwater, while blackspotted sticklebacks (<em>Gasterosteus wheatlandi</em>) and the &ldquo;white&rdquo; threespine stickleback ecotype (<em>Gasterosteus aculeatus</em>) are restricted to brackish or saltwater when breeding. I investigated if blackspotted and white threespine distribution might be limited by low freshwater tolerance during early life or when combined with cold temperatures, as occurs during over-wintering. I found blackspotted sticklebacks have relatively poor freshwater fertilization success, but all species had similar freshwater survivorship, development, and embryonic metabolic rates. Upon exposure to warm (18&deg;C) and cold (4&deg;C) freshwater and saltwater, adult blackspotted and threespine sticklebacks demonstrated similar standard and active metabolic rates, survival, growth, and hepatic protein synthesis rates. My results suggest blackspotted freshwater colonization might be limited by fertilization, but not by early life freshwater tolerance or the cold-stress combination as adults.</p>