| Summary: | Degree: Master of Science Abstract: Northern form Dolly Varden char (Salvelinus malma malma) inhabit cold-water streams in the western Canadian Arctic. They are an important cultural and subsistence resource to local Aboriginal communities, yet little is known about their complex early life histories. Populations of Dolly Varden exhibit partial anadromy, where a portion of the population migrates to the ocean to feed in productive coastal waters (anadromous), while other individuals remain in freshwater year-round (residents). Residents are ‘sneak’ spawners and benefit from early maturation, while fish that migrate benefit from a larger size-at-maturation and thus a competitive advantage for spawning opportunities. According to classical life history theory, in populations that are partially anadromous, fast growing fish should migrate sooner and at smaller sizes than slow growing individuals, and the fastest growers in the population should remain as stream residents. Dolly Varden were sampled from three river systems (Rat, Big Fish, and Babbage rivers) and otoliths were used to assess size-at-age and growth patterns through back-calculation, and age-at-migration through strontium analysis. Otoliths were used as proxy measures for fish growth and size-at-age due to their ability to record life history events throughout the lifetime of the fish. Initially, the fish length – otolith length relationship was observed in order to verify proportional growth between the fish and otolith. However, a decoupling was detected during first migration where fish size dramatically increased but otolith growth did not accrete material to the same extent. Modified back-calculation equations were developed to account for this decoupling based on discontinuous piecewise regressions. The new biological intercept breakpoint method provided the most accurate representation of fish size-at-age throughout all life history stages when compared to known capture values in fish, although traditional back-calculation methods also reflected ...
|
|---|