MEPS 532:197-211 (2015)  -  DOI: https://doi.org/10.3354/meps11330

The role of habitat complexity in shaping the size structure of a temperate reef fish community

Rowan Trebilco1,2,*, Nicholas K. Dulvy1, Hannah Stewart3, Anne K. Salomon4,*

1Earth to Ocean Research Group, Biological Sciences, Simon Fraser University, 8888 University Drive, Burnaby, BC, Canada V5A 1S6
2Antarctic Climate and Ecosystems Cooperative Research Centre, University of Tasmania, Private Bag 80, Hobart, TAS 7001 Australia
3West Vancouver Labs, Fisheries and Oceans Canada, 4160 Marine Drive, West Vancouver, BC, Canada V7V 1N6
4School of Resource and Environmental Management, Simon Fraser University, 8888 University Drive, Burnaby, BC, Canada V5A 1S6

ABSTRACT: Understanding how habitat complexity shapes fish communities is necessary to predict the consequences of future habitat change. On temperate rocky reefs, the presence and characteristics of canopy-forming kelps and the architectural complexity, or rugosity, of the underlying rocky substratum are foundational elements of habitat complexity. However, it is not yet clear how these factors shape the size structure of rocky-reef-associated fish communities. Here, we use biomass spectrum models to evaluate how fish community size structure in high-latitude rocky-reef kelp forests is shaped by substratum rugosity and the degree of closure and density of the kelp canopy. We found that the presence of a closed kelp canopy was associated with an average 75% increase in overall fish biomass compared to open-canopy reefs. Furthermore, on the highest-rugosity reefs, the biomass of small fishes (32-64 g) was 800% higher than on the lowest-rugosity reefs, while large fish (1-2 kg) biomass was 60% lower. Consequently, biomass was more evenly distributed across body-size classes on high-rugosity reefs. By decomposing the biomass spectrum into total biomass and mean individual body mass, we found that higher kelp stipe densities also tended to be associated with larger fishes, but this effect was outweighed by the tendency for more small-bodied fishes with increasing rugosity. This study demonstrates how size-based analyses can give new insights into the ecology of temperate reef communities, and may be useful for tracking changes in kelp-associated assemblages in the coming decades with the maturation of marine protected areas, the recovery of sea otter populations, and changing climate.


KEY WORDS: Biomass size spectra · Community ecology · Coral reef · Ecosystem baseline · Energy flow · Foundation species


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Cite this article as: Trebilco R, Dulvy NK, Stewart H, Salomon AK (2015) The role of habitat complexity in shaping the size structure of a temperate reef fish community. Mar Ecol Prog Ser 532:197-211. https://doi.org/10.3354/meps11330

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