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Marine Biology Graduate Student Association

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Michael Schram

Michael Schram

Fish Ecology Lab
Department of Biology

18111 Nordhoff Street

Northridge, CA 91330-8303


B.S. Marine Biology, Cal State Northridge, 2010

Research Interests

Reproductive ecology
Sex-changing species
Anthropogenic impacts on marine fishes

Thesis: The effects of size-selective harvesting on an unexploited protogynous temperate reef fish, Rhinogobiops nicholsii

Evolutionary history and current pressures influence the life-history characteristics exhibited by individuals in a population. Current pressures may come from the natural environment or anthropogenic sources. Typically, fisheries disproportionately target larger individuals in populations. Focusing on the largest individuals produces artificial selection pressure against certain sizes and traits that determine size. For protogynous hermaphrodites, natural selection favors individuals that reach large size rapidly and change sex. Harvesting the largest individuals removes males, further skewing an already skewed sex ratio, and may decrease the frequency of certain growth traits.

blackeye goby

Observational studies have established correlative relationships between fishing intensity and size at maturity and size at sex-change in hermaphroditic fishes. However, a controlled manipulative study looking at the direct effects of size-selective harvesting on protogynous hermaphrodites has not been conducted. To address this, I will use the abundant, non-harvested, protogynous blackeye goby (Rhinogobiops nicholsii) inhabit artificial 1-m2 rock rubble reefs subjected to varying size-selective removal treatments. Reproductive output and growth rates will be assessed for each treatment over a six week period following removals. My research is expected to establish a direct causal relationship between size-selective harvesting and reproduction and growth in protogynous hermaphrodites.

experimental setup fish