Autumn distribution of Bristol Bay red king crab using fishery logbooks.

Spatial distributions of fished species must be well characterized to avoid local depletions, identify critical habitat, and predict and mitigate interactions with other fisheries. The Bristol Bay red king crab (Paralithodes camtschaticus) fishery is one of the largest crab fisheries in Alaska. Summer crab distributions have been well documented by decades of bottom trawl surveys. However, crab movement and distribution are poorly understood outside the summer survey period, which creates several management challenges. One important component of fishery management is the existence of no-trawl zones, which are intended to protect crab from bottom trawl fisheries. However, it is difficult to evaluate the placement of no-trawl zones, because most crab bycatch occurs in trawl fisheries during winter when crab distributions are unknown. Daily fishing logs, kept by skippers in the red king crab fleet since 2005, contain detailed information on the spatial distribution of catch and effort of legal sized male crab during the autumn crab fishery. However, data contained in these hand-written logbooks have not been readily accessible. We digitized daily fishing logs from 2005 to 2016 and used spatial information on catch and effort to infer geographic distributions of legal sized male king crab during the crab fishing season. Changes in distribution were tracked across this 12-yr period and comparisons were made between warm and cold temperature regimes. In warm years (2005, 2014-2016), crab aggregated in the center of Bristol Bay, Alaska, while in cold years (2007-2013) they were closer to the Alaska Peninsula. The majority of crab were caught in no-trawl areas (63.4% on average), but variations occurred among years and with temperature regime (40.0-86.8% in no-trawl zones). As temperatures continue to shift in the Bering Sea, it will be important to continue monitoring crab distributions outside the summer survey period.

Larval Biology and Environmental Tolerances of the King Crab Parasite Briarosaccus regalis.

Rhizocephalan barnacles in the genus Briarosaccus parasitize and castrate king crab hosts, thereby preventing host reproduction and potentially altering host abundance. To better understand how environmental factors in Alaska may influence Briarosaccus prevalence, we studied the effects of temperature and salinity on the larvae of Briarosaccus regalis (previously Briarosaccus callosus). Nauplius larvae were reared at 7 temperatures (2 to 16 C) and 8 salinities (19 to 40) to determine larval survival and development rates. Maximum survival occurred from 4 to 12 C and at salinities between 25 and 34. In the Gulf of Alaska and Bering Sea, ocean temperatures and salinities are often within these ranges; thus current conditions appear favorable for high B. regalis larval survival. In addition, temperature was negatively correlated with larval development time; thus warmer waters can reduce the time larvae are exposed to the dangers of the planktonic environment. Since only female B. regalis larvae can infect crabs, we investigated the sex ratios of B. regalis broods at different temperatures and how size and morphological traits can be used to sex cyprid larvae. Larval rearing temperature did not affect brood sex ratio (F0.947, P = 0.369), but sex ratio varied among broods (F221.9; P < 0.001). Male larvae (424.5 ± 24.3 µm [mean ± 1 SD]) were significantly larger than female larvae (387.6 ± 22.7 µm [mean ± 1 SD]; F1,221.4; P < 0.001), consistent with other rhizocephalan cyprids, but sizes overlapped between the sexes such that morphological traits were also necessary for determining sex. Overall, this study provides new information on the larval biology, larval morphology, and environmental tolerances of B. regalis , an important king crab parasite.

The dynamics of biogeographic ranges in the deep sea.

Anthropogenic disturbances such as fishing, mining, oil drilling, bioprospecting, warming, and acidification in the deep sea are increasing, yet generalities about deep-sea biogeography remain elusive. Owing to the lack of perceived environmental variability and geographical barriers, ranges of deep-sea species were traditionally assumed to be exceedingly large. In contrast, seamount and chemosynthetic habitats with reported high endemicity challenge the broad applicability of a single biogeographic paradigm for the deep sea. New research benefiting from higher resolution sampling, molecular methods and public databases can now more rigorously examine dispersal distances and species ranges on the vast ocean floor. Here, we explore the major outstanding questions in deep-sea biogeography. Based on current evidence, many taxa appear broadly distributed across the deep sea, a pattern replicated in both the abyssal plains and specialized environments such as hydrothermal vents. Cold waters may slow larval metabolism and development augmenting the great intrinsic ability for dispersal among many deep-sea species. Currents, environmental shifts, and topography can prove to be dispersal barriers but are often semipermeable. Evidence of historical events such as points of faunal origin and climatic fluctuations are also evident in contemporary biogeographic ranges. Continued synthetic analysis, database construction, theoretical advancement and field sampling will be required to further refine hypotheses regarding deep-sea biogeography.