Widespread and increasing near-bottom hypoxia in the coastal ocean off the United States Pacific Northwest.

The 2021 summer upwelling season off the United States Pacific Northwest coast was unusually strong leading to widespread near-bottom, low-oxygen waters. During summer 2021, an unprecedented number of ship- and underwater glider-based measurements of dissolved oxygen were made in this region. Near-bottom hypoxia, that is dissolved oxygen less than 61 µmol kg-1 and harmful to marine animals, was observed over nearly half of the continental shelf inshore of the 200-m isobath, covering 15,500 square kilometers. A mid-shelf ribbon with near-bottom, dissolved oxygen less than 50 µmol kg-1 extended for 450 km off north-central Oregon and Washington. Spatial patterns in near-bottom oxygen are related to the continental shelf width and other features of the region. Maps of near-bottom oxygen since 1950 show a consistent trend toward lower oxygen levels over time. The fraction of near-bottom water inshore of the 200-m isobath that is hypoxic on average during the summer upwelling season increases over time from nearly absent (2%) in 1950-1980, to 24% in 2009-2018, compared with 56% during the anomalously strong upwelling conditions in 2021. Widespread and increasing near-bottom hypoxia is consistent with increased upwelling-favorable wind forcing under climate change.

Sex matters: Otolith shape and genomic variation in deacon rockfish (Sebastes diaconus).

Little is known about intraspecific variation within the deacon rockfish (Sebastes diaconus), a recently described species found in the northeast Pacific Ocean. We investigated population structure among fish sampled from two nearshore reefs (Siletz Reef and Seal Rock) and one offshore site (Stonewall Bank) within a <50-km2 area off the Oregon coast. Fish from the three sample sites exhibited small but statistically significant differences based on genetic variation at >15,000 neutral loci, whether analyzed independently or classified into nearshore and offshore groups. Male and females were readily distinguished using genetic data and 92 outlier loci were associated with sex, potentially indicating differential selection between males and females. Morphometric results indicated that there was significant secondary sexual dimorphism in otolith shape, but further sampling is required to disentangle potential confounding influence of age. This study is the first step toward understanding intraspecific variation within the deacon rockfish and the potential management implications. Since differentiation among the three sample sites was small, we consider the results to be suggestive of a single stock. However, future studies should evaluate how the stock is affected by differences in sex, age, and gene flow between the nearshore and offshore environments.

The biology, ecology and fishery of the Dungeness crab, Cancer magister.

The Dungeness crab, Cancer magister, is a commercially important crustacean that ranges from the Pribilof Islands, Alaska, to Santa Barbara, California. Mating occurs between recently moulted females and post-moult males. After approximately 90 days, females release planktonic larvae into the water column. Stage-I zoea are found in the nearshore environment and subsequent zoeal stages are found at greater distances. After approximately 80 days, zoea moult into megalopa, which move first from the open ocean onto the continental shelf and then across the shelf to settle in the nearshore environment or estuaries. Crabs reach sexual maturity at 2-3 years of age. The fishery for C. magister is managed using a 3-S management strategy which regulates catch based on size, sex and season. As more fisheries seek sustainability certifications, the Dungeness crab fishery presents an excellent test case of how to sustainably manage a crustacean fishery.