As the oceans absorb anthropogenic CO2 they become more acidic, a problem termed ocean acidification (OA). Since this increase in CO2 is occurring rapidly, OA may have profound implications for marine ecosystems. In the temperate northeast Pacific, fisheries play key economic and cultural roles and provide significant employment, especially in rural areas. In British Columbia (BC), sport (recreational) fishing generates more income than commercial fishing (including the expanding aquaculture industry). Salmon (fished recreationally and farmed) and Pacific Halibut are responsible for the majority of fishery-related income. This region naturally has relatively acidic (low pH) waters due to ocean circulation, and so may be particularly vulnerable to OA. We have analyzed available data to provide a current description of the marine ecosystem, focusing on vertical distributions of commercially harvested groups in BC in the context of local carbon and pH conditions. We then evaluated the potential impact of OA on this temperate marine system using currently available studies. Our results highlight significant knowledge gaps. Above trophic levels 2–3 (where most local fishery-income is generated), little is known about the direct impact of OA, and more importantly about the combined impact of multi-stressors, like temperature, that are also changing as our climate changes. There is evidence that OA may have indirect negative impacts on finfish through changes at lower trophic levels and in habitats. In particular, OA may lead to increased fish-killing algal blooms that can affect the lucrative salmon aquaculture industry. On the other hand, some species of locally farmed shellfish have been well-studied and exhibit significant negative direct impacts associated with OA, especially at the larval stage. We summarize the direct and indirect impacts of OA on all groups of marine organisms in this region and provide conclusions, ordered by immediacy and certainty.

The Sechelt Inlet complex (British Columbia, Canada), Including Narrows and Salmon Inlets, was sampled from h4ay 1988 to September 1990 in order to d e s c r~b e the nutrient and plankton regimes. Species succession w i t h~n the inlet was typical for temperate unpolluted waters despite aquaculture activity and nutrient-loading from the town of Sechelt at the southern end. The N : P ratio in the upper 21 m of 8.3, which is well below the Redfield ratio of 16, suggests an N-limited system. The ratio is also lower than those found in adjacent systems, and supports the a s s u~n p t~o n that Sechelt Inlet is the least influenced by oceanic waters. The N : P ratio also c o~n c~d e s with the optimum ratio for Skeletonerna costaturn of 8.1 which suggests that either the system provided an optimal nutrient regime for this diatom or the dominance of S. costatum determined ambient N:P ratios. The spring bloom, dominated by S. costatum and ThalaSS~~Sira nordenskioeldii, occurred early (in March) due to the combined influence of stratification, created by runoff from Salmon Inlet, and shelter from wind exposure. By summer the waters became depleted of nitrate down to 5 m, and nanoplankton, composed chiefly of cryptomonads and Chrysochrornulina spp., prevailed. Bimodal peaks in nanoflagellate biomass occurred each summer, with the cryptomonads remaining regular components. Under normal meteorological conditions Chrysochromulina spp. \vould codominate but during 1989, storm activity in May somehow caused the replacement of the prymnesiomonads by the silicoflagellate Dictyocha speculurn. The latter occurred In ~t s askeletal form during the late summer nanoflagellate peak. The water injected through the mouth of Sechelt Inlet by a tidal jet combined with water overlying the anoxic bottom of inner Narrows Inlet and caused stimulation of plankton growth at the confluence of these 2 inlets. There was also h~g h biomass at the shallow southern end possibly due to increased mixing over a sill and m~l d eutrophication.

Abstract. The northern Strait of Georgia, British Columbia, Canada, was sampled five times between March and September 1986, employing a grid of stations spanning the strait. The spring diatom bloom was not observed and may have been suppressed by a combination of wind exposure and grazing by microzooplankton, notably non-loricate oligotrichs and the dinoflagellate Gyrodinium spirale. Macrozooplankton were not studied. By June, the ecosystem was dominated by flagellates, and ciliate biomass was three times greater than that of the nanoflagellates. The photosynthetic dominant Heterosigma akashiwo was possibly inhibiting diatom growth, as environmental conditions were conducive to the latter's growth. During late summer (August-September), surface waters became nutrient-depleted and a mosaic of organismal types was formed. The pattern included diatoms on the more turbulent west side, nanoflagellates on the more stable east side, and dinoflagellates in the north associated with frontal boundaries. The driving force behind the mosaic appeared to be tidal turbulence and was most effective at times of advanced water-column stratification. Other points of interest were subsurface concentrations of Chaetoceros species, which were perhaps maintained at the pycnocline by entrainment in areas of high tidal turbulence, and a large ratio of heterotrophic to photoautotrophic biomass, possibly due to mixotrophy in ciliates.

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Schnute, J. T. and Haigh, R. 2007. Compositional analysis of catch curve data, with an application to Sebastes maliger. – ICES Journal of Marine Science, 64: 218–233. This paper applies modern compositional analysis to catch curve data from a quillback rockfish (Sebastes maliger) population in British Columbia, Canada. Bubble plots and ternary diagrams portray variable age distributions and highlight distinctions between commercial and survey sample data. The models formalize important historical issues in catch curve analysis related to selectivity and recruitment variability, where a particular model corresponds to a prescribed vector of design parameters. The roles that compositional distributions (multinomial, Dirichlet, logistic-normal) can play in fishery data analysis are described, and Bayesian methods are used to examine how the distribution of a key mortality parameter depends on model choice. The framework provides a direct link between model designs and policy outcomes that depend on estimated mortalities or mortality ratios.

Spatial and temporal distributions of Chaetoceros convolutum (including C. concavicorne), Heterosigma akashiwo, Protogonyaulax (= Alexandrium) catenella, and Dinophysis are presented for the northern Strait of Georgia from March to September, 1986. In spring C. convolutum was found on the slightly stratified eastern side in concentrations just below those leading to kills of caged salmon (4-5000 cells∙L−1). The northern Strait became thermally stratified in summer. At this time the population centre of C. convolutum shifted to mid-Strait near the edge of the Discovery Passage tidal jet where it was maintained near the pycnocline (10–15 m) in concentrations up to 35,000 cells∙L−1. Heterosigma akashiwo, another fish killer, was the pbotosynthetic dominant in June and reached 200 000 cells∙L−1 in the northwest at 5 m. Protogonyaulax catenella, a source of paralytic shellfish poison (PSP), was also most abundant in the north and west, where dangerous levels of PSP often occur, particularly near Comox. Collectively, Dinophysis species exceeded the critical concentration for diarrheic shellfish poisoning (200 cells∙L−) on the western side during summer. All the potentially harmful flagellated species seem to be introduced from the northern passageways. Sheltered bays to the north are possible seed beds for cyst-forming species whereas C. convolutum remains in the Strait year-round.

This paper describes a convenient simulation model, based on the compound binomial-gamma distribution, to assist the planning and design of groundfish trawl surveys. The analysis uses swept-area density measurements from stratified tows to give a simple nonparametric biomass estimate. A parametric simulation model requires only three input parameters for each stratum, which can be estimated initially from past surveys or commercial fishery data. Analytical results provide intuitive algorithms for estimating variances, investigating tow allocation strategies, and exploring potential survey results. Simulations make it possible to compare the estimated biomass with its true value and to assess coverage properties of confidence intervals obtained from bootstraps. Bias correction and acceleration both improve the results, but small samples taken from populations with highly variable densities tend to produce underestimates of available biomass. The simulation framework allows easy adaptation to address broader issues, such as the design of a multispecies survey.

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