Prevalence and Intensity of Otodistomum hydrolagi (Trematoda: Azygiidae) in Spotted Ratfish, Hydrolagus colliei (Chondrichthyes: Chimaeridae) from the Coastal Waters of British Columbia, Canada.

The prevalence and intensity of the trematode, Otodistomum hydrolagi, were determined for the first time in Spotted Ratfish, Hydrolagus colliei. Spotted Ratfish specimens were collected during bottom-trawl surveys in Queen Charlotte Sound (QCS, n = 31) and off the west coast of Vancouver Island (WCVI, n = 242). In all instances, the flukes were found within the abdominal cavity. Most flukes were mature (intrauterine eggs were present) and ranged in length from 9.1 to 61.5 mm, with a mean ± SD length of 28.5 ± 12.1 mm (n = 52). Fluke length was positively correlated with Spotted Ratfish precaudal length (PCL), and no Spotted Ratfish smaller than 247-mm PCL was infected by O. hydrolagi. The overall prevalence (95% confidence interval [CI]) and mean intensity (95% CI) of O. hydrolagi were 27.8% (22.6-33.6) and 1.24 (1.09-1.43), respectively. Neither prevalence nor mean intensity differed between host location or host sex. The majority (86%) of infected hosts harbored a single fluke (range 1-5), but 4 Spotted Ratfish were infected with 3 or more flukes, which accounted for 16% of all observed O. hydrolagi. The fluke population exhibited an aggregated distribution with 80% of individuals found in 21% of the hosts, but among infected hosts there was low variability in the intensity of infection. This is the first ecological study of O. hydrolagi from its Spotted Ratfish host, and the first record of this trematode in Canadian waters, which extends the range of O. hydrolagi to include Canadian coastal Pacific waters.

Subregional differences in groundfish distributional responses to anomalous ocean bottom temperatures in the northeast Pacific.

Although climate-induced shifts in fish distribution have been widely reported at the population level, studies that account for ontogenetic shifts and subregional differences when assessing responses are rare.In this study, groundfish distributional changes in depth, latitude, and longitude were assessed at different size classes by species within nine subregions. We examined large, quality-controlled datasets of depth-stratified-random bottom trawl surveys conducted during summer in three large regions-the Gulf of Alaska and the west coasts of Canada and the United States-over the period 1996-2015, a time period punctuated by a marine "heat wave." Temporal biases in bottom temperature were minimized by subdividing each region into three subregions, each with short-duration surveys. Near-bottom temperatures, weighted by stratum area, were unsynchronized across subregions and exhibited varying subregional interannual variability. The weighted mean bottom depths in the subregions also vary largely among subregions. The centroids (centers of gravity) of groundfish distribution were weighted with catch per unit effort and stratum area for 10 commercially important groundfish species by size class and subregion. Our multivariate analyses showed that there were significant differences in aggregate fish movement responses to warm temperatures across subregions but not among species or sizes. Groundfish demonstrated poleward responses to warming temperatures only in a few subregions and moved shallower or deeper to seek colder waters. The temperature responses of groundfish depended on where they were. Under global warming, groundfish may form geographically distinct thermal ecoregions along the northeast Pacific shelf. Shallow-depth species exhibited greatly different distributional responses to temperature changes across subregions while deep-depth species of different subregions tend to have relatively similar temperature responses. Future climate studies would benefit by considering fish distributions on small subregional scales.

General effects of climate change on Arctic fishes and fish populations.

Projected shifts in climate forcing variables such as temperature and precipitation are of great relevance to arctic freshwater ecosystems and biota. These will result in many direct and indirect effects upon the ecosystems and fish present therein. Shifts projected for fish populations will range from positive to negative in overall effect, differ among species and also among populations within species depending upon their biology and tolerances, and will be integrated by the fish within their local aquascapes. This results in a wide range of future possibilities for arctic freshwater and diadromous fishes. Owing to a dearth of basic knowledge regarding fish biology and habitat interactions in the north, complicated by scaling issues and uncertainty in future climate projections, only qualitative scenarios can be developed in most cases. This limits preparedness to meet challenges of climate change in the Arctic with respect to fish and fisheries.

An overview of effects of climate change on selected arctic freshwater and anadromous fishes.

Arctic freshwater and diadromous fish species will respond to the various effects of climate change in many ways. For wide-ranging species, many of which are key components of northern aquatic ecosystems and fisheries, there is a large range of possible responses due to inter- and intra-specific variation, differences in the effects of climate drivers within ACIA regions, and differences in drivers among regions. All this diversity, coupled with limited understanding of fish responses to climate parameters generally, permits enumeration only of a range of possible responses which are developed here for selected important fishes. Accordingly, in-depth examination is required of possible effects within species within ACIA regions, as well as comparative studies across regions. Two particularly important species (Arctic char and Atlantic salmon) are examined as case studies to provide background for such studies.

Male nest site fidelity and female serial polyandry in lingcod (Ophiodon elongatus, Hexagrammidae).

Nest site fidelity and serial polyandry were examined in lingcod, Ophiodon elongatus, a teleost fish in which the nest-guarding male parent invests more heavily in parental care than the elusive female parent. Lingcod parental and progeny genotypes were established for fish spawning on a 200 m(2) section of Snake Island reef, British Columbia in two successive years to evaluate male and female mate choice (monogamy or polygamy) and nest site reuse by the same parents (nest site fidelity) and/or different parents (nest site affinity). Thirteen nests (egg masses) guarded by nine males and 14 nests guarded by seven males were observed in 2002 and 2003, respectively. No female laid more than one nest per season or spawned in the study area in both years. In contrast, at least six (86%) and possibly all seven (100%) of the 2003 guardian males had been guardian or auxiliary males in 2002. Both nest site affinity and extreme male nest site fidelity were observed, with at least four males reusing the exact same nest site. Serial polyandry resulting from the high male and low female nest site fidelity is consistent with predictions based on a low female parental investment and high rate of progeny loss to predation and cannibalism. Male polygyny, achieved primarily by cuckoldry within seasons, was enhanced by the lack of female fidelity between seasons. Polygamy in both sexes of nest-tending marine fish may minimize reproductive skew and maximize genetic diversity within populations.