Cumulative effects of long-term anthropogenic impacts on resident fish communities in subarctic fishing harbours

Ecosystems perceived to have sustained historical human pressure from multiple stressors are often considered to be degraded. Diversity and abundance of marine macroflora and macrofauna were observed at 17 harbour sites in Newfoundland (Canada) over four consecutive years (2008–2011), to determine cumulative effects of long-term anthropogenic impacts on coastal marine biota in small fishing harbours. A Principal Component Analysis was applied to evaluate the relative effects of physical harbour characteristics (harbour shape, size, and orientation), and those directly associated with anthropogenic influence (current and historical human population size, human landscape “footprint”, and operating capacity of the local fishing industry), on marine vegetation, fish, and invertebrate macrofauna. The first three principal components explained 77% of the cumulative variance of the physical harbour and anthropogenic variables. PC1 was dominated by variables associated with human use, and site depth; PC2 was associated with physical site orientation and the cumulative wharf length; and PC3 was associated with long-term use and harbour area. The densities of cod (Gadus spp.) and crab species increased significantly along the gradient of human impact metrics, while winter flounder (Pseudopleuronectes americanus), cunner (Tautogolaborus adspersus) and shorthorn sculpin (Myoxocephalus scorpius) decreased. Sessile fauna diversity and density, and flora percent cover correlated with long-term use and harbour area. Species densities changed in response to cumulative effects of long term human settlement near harbours, but prominent species were ubiquitous in these coastal ecosystems.