Fisheries and aquaculture

A heaping pile of dead silver-coloured fish of a small size.
Photo by Allan Bolton

Fisheries and aquaculture are an especially important sector for coastal communities and First Nations. For many, fishing is a way of life which cannot be measured by the contribution to the economy alone, as the social and cultural values play a large role. Existing stresses and impacts on BC’s coastal fisheries are expected to be exacerbated by climate change, and in some cases (such as salmon), these impacts are already evident. The fishing industry has already declined significantly across the province: since the 1980s, the fishing fleet has shrunk by 60% and there are 70% fewer fishers employed in the industry [91]. The effects of climate change on fisheries in this region are reflected in projected species range shifts, in that the abundance of current target species is projected to decrease, and that the species currently available across the region are likely to change [12,17,92,93]. The impacts of these projected changes in fisheries catches could lead to or amplify other socio-economic impacts of climate change on fisheries and communities through reduced food security and economic loss [92].

Sea level rise

The associated impacts of sea level rise on land erosion and increased runoff is likely to directly affect nearshore species, especially filter feeders (shellfish) if water quality declines. Existing shellfish beds are likely to be affected, which will have implications for many species which depend upon the intertidal ecosystem for habitat and food, especially as juveniles (salmon, crab, eelgrass, algae, clams, humans) [94]. Spawning habitat for forage fish, and rearing habitats for invertebrates, could decrease or be lost due to erosion, subsidence, and submersion due to sea level rise [29]. This may be particularly problematic for Pacific herring, as that species prefers coastal marine algal species for spawning substrate, habitats that may potentially be lost as sea levels rise [29].

Sea surface temperature

The associated impacts of sea level rise on land erosion and increased runoff is likely to directly affect nearshore species, especially filter feeders (shellfish) if water quality declines. Existing shellfish beds are likely to be affected, which will have implications for many species which depend upon the intertidal ecosystem for habitat and food, especially as juveniles (salmon, crab, eelgrass, algae, clams, humans) [94]. Spawning habitat for forage fish, and rearing habitats for invertebrates, could decrease or be lost due to erosion, subsidence, and submersion due to sea level rise [29]. This may be particularly problematic for Pacific herring, as that species prefers coastal marine algal species for spawning substrate, habitats that may potentially be lost as sea levels rise [29].

Ocean Acidification

The effects of ocean acidification on fisheries are largely unknown, including on the important salmon and Pacific halibut fisheries [27,43; Appendix Table 2). In tropical fish, ocean acidification affects behaviour and results in increased mortality, but species responses in temperate regions are unknown [52]. Adult fish may be more tolerant of ocean acidification than early development stages, but there is limited research on life stage specific responses to pH for BC fishes specifically [52].

The effects of ocean acidification on shelled organisms, however, are much more understood ([52,99–101]. Aquaculture has the potential to improve food security and support remote economies. Across BC, capture fisheries landings are either in decline or somewhat stable, while aquaculture continues to grow (with some exceptions due to recent ocean acidification issues, e.g. Strait of Georgia, [102]). In the MaPP region, aquaculture is of great interest to coastal communities and First Nations. Currently, aquaculture operations in BC focus on salmon and other finfish, as well as shellfish including oysters and geoduck clams. Ocean acidification is likely to negatively affect shellfish aquaculture [99], and changes to oceanographic conditions including acidification are likely to affect finfish aquaculture as well [52]. The specific effects of ocean acidification on shelled molluscs varies by species, and a recent review suggested that acidification most negatively affects survival and shell growth (calcification), followed by respiration and clearance rates [99].

Ocean deoxygenation

Ocean deoxygenation will affect commercial fish species by reducing high quality fish habitat. Declining oxygen levels across the Pacific Ocean will contribute to the general decline and potential collapse of sessile (immobile) marine species, or sediment-dwelling organisms, as well as any other species who are intolerant of low oxygen levels. Declining oxygen levels are likely to especially affect groundfish species, whose habitat seems to already be decreasing by 2-3m per year, potentially related to declining oxygen levels [4]. Declining oxygen levels, and increasing hypoxia, will also likely affect aquaculture operations for vulnerable species, such as Dungeness crab and spot prawns [29]. Some hypoxia tolerant species (e.g. squid, jellyfish) may increase in abundance and/or distribution, potentially outcompeting less tolerant species (e.g. finfish) [54, 77].

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