Acoustic-trawl surveys use trawl catches to validate the species and size composition of fish aggregations detected acoustically. However, certain sizes of fish may be more likely to escape some trawls, which can bias the size and age distribution of the catch used to estimate biomass. To quantify size-selectivity, we studied 3 midwater trawls used for the United States and Canada joint survey of Pacific hake (Merluccius productus). The survey most recently used an Aleutian Wing Trawl (AWT) with different codend liners until 2023, then switched to a Multi-Function Trawl (MFT) in 2025. To prepare for the switch, we assessed differences in escapement and catch rates using recapture nets, and in paired trawls of both net-types sampling the same aggregations. All nets retained greater than 85% of hake longer than 30-cm (age 2+). In general, the MFT was more efficient than the AWT, with near full retention of all sizes. A substantial fraction of small hake (age 0 to 1) escaped the AWT. A power analysis indicated a low probability of detecting differences in escapement from the AWT with different liners. Gear selectivity information is important to improve the accuracy of fishery survey data and account for changes in sampling gear.

In the California Current Ecosystem, the California Undercurrent (CU) is the predominate subsurface current that transports nutrient-rich water from southern California poleward. In this study, we used a large dataset of spatially explicit in situ observations of Pacific hake ( Merluccius productus) and the CU (36.5–48.3°N) to estimate relationships between northward undercurrent velocity and hake distribution and determine whether these relationships vary across space or life-history stage. We found that both hake occurrence and density had strong spatially complex relationships with the CU. In areas north of 44°N (central Oregon), the CU effect was spatially consistent and opposite for occurrence (negative) and density (positive), indicating that hake may aggregate in areas of high northward velocity in this region. In areas south of 44°N, the CU effect showed a cross-shelf gradient for both occurrence and density, indicating a more nearshore hake distribution when northward velocity is higher in this region. Together, our results suggest that future changes in the CU due to climate change are likely to impact hake differently in northern and southern areas.

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.

Generating biomass-at-age indices for fisheries stock assessments with acoustic data collected by uncrewed surface vessels (USVs) has been hampered by the need to resolve acoustic backscatter with contemporaneous biological (e.g., age) composition data. To address this limitation, Pacific hake ( Merluccius productus ; “hake”) acoustic data were gathered from a USV survey (in 2019) and acoustic-trawl survey (ATS; 2019 and eight previous years), and biological data were gathered from fishery-dependent and non-target (i.e., not specifically targeting hake) fishery-independent sources (2019 and eight previous years). To overcome the lack of contemporaneous biological sampling in the USV survey, age class compositions were estimated from a generalized linear mixed spatio-temporal model (STM) fit to the fishery-dependent and non-target fishery-independent data. The validity of the STM age composition estimation procedure was assessed by comparing estimates to age compositions from the ATS in each year. Hake biomass-at-age was estimated from all combinations of acoustics (USV or ATS in 2019, ATS only in other years) and age composition information (STM or ATS in all years). Across the survey area, proportional age class compositions derived from the best STM differed from ATS observations by 0.09 on average in 2019 (median relative error (MRE): 19.45%) and 0.14 across all years (MRE: 79.03%). In data-rich areas (i.e., areas with regular fishery operations), proportional age class compositions from the STM differed from ATS observations by 0.03 on average in 2019 (MRE: 11.46%) and 0.09 across years (MRE: 54.96%). On average, total biomass estimates derived using STM age compositions differed from ATS age composition-based estimates by approximately 7% across the study period (~ 3% in 2019) given the same source of acoustic data. When biomass estimates from different sources of acoustic data (USV or ATS) were compared given the same source of age composition data, differences were nearly ten-fold greater (22% or 27%, depending on if ATS or STM age compositions were used). STMs fit to non-contemporaneous data may provide suitable information for assigning population structure to acoustic backscatter in data-rich areas, but advancements in acoustic data processing (e.g., automated echo classification) may be needed to generate viable USV-based estimates of biomass-at-age.

Introduction Understanding how abundance, productivity and distribution of individual species may respond to climate change is a critical first step towards anticipating alterations in marine ecosystem structure and function, as well as developing strategies to adapt to the full range of potential changes. Methods This study applies the NOAA (National Oceanic and Atmospheric Administration) Fisheries Climate Vulnerability Assessment method to 64 federally-managed species in the California Current Large Marine Ecosystem to assess their vulnerability to climate change, where vulnerability is a function of a species’ exposure to environmental change and its biological sensitivity to a set of environmental conditions, which includes components of its resiliency and adaptive capacity to respond to these new conditions. Results Overall, two-thirds of the species were judged to have Moderate or greater vulnerability to climate change, and only one species was anticipated to have a positive response. Species classified as Highly or Very Highly vulnerable share one or more characteristics including: 1) having complex life histories that utilize a wide range of freshwater and marine habitats; 2) having habitat specialization, particularly for areas that are likely to experience increased hypoxia; 3) having long lifespans and low population growth rates; and/or 4) being of high commercial value combined with impacts from non-climate stressors such as anthropogenic habitat degradation. Species with Low or Moderate vulnerability are either habitat generalists, occupy deep-water habitats or are highly mobile and likely to shift their ranges. Discussion As climate-related changes intensify, this work provides key information for both scientists and managers as they address the long-term sustainability of fisheries in the region. This information can inform near-term advice for prioritizing species-level data collection and research on climate impacts, help managers to determine when and where a precautionary approach might be warranted, in harvest or other management decisions, and help identify habitats or life history stages that might be especially effective to protect or restore.

Advances in acoustics technologies offer a remote and non-invasive sensing means to conduct fisheries acoustic surveys. Over the past two decades, joint US and Canada acoustic and trawl surveys on Pacific hake (Merluccius productus), one of the most important commercial fisheries off the West Coasts of the United States and Canada, have been conducted at the intervals of one to three years within the California Current System (CCS). In this presentation, the temporal and spatial distributions of Pacific hake resulting from these surveys spanning a period of nearly two decades will be presented. Challenges in converting the measured acoustic quantities to biological quantities, such as abundance and biomass, will be addressed, including uncertainties associated with mixed species, environmental parameters, and properties in fish morphology and anatomy. Issues related to transitions from single-species to ecosystem-based acoustic surveys will also be discussed.

The population of Humboldt squid (Dosidicus gigas) has seen an explosion in the Eastern North Pacific over the last several years. The species has gone from being rarely seen in the waters off OR, WA, and BC to becoming a major predator in the marine food web in this area. This population explosion has the potential to cause large impacts in major fish stocks. The biennial 2009 Joint U.S.-Canada Pacific hake (Merluccius productus) acoustic trawl survey also noted large amounts of Humboldt over much of the survey area. Because Humboldt squid could be acoustically confused with Pacific hake, and because the presence of Humboldt squid disrupted the normal shoaling pattern of hake, an estimated depth threshold was used to help distinguish Humboldt squid from hake. Accordingly, the biomass estimate of Pacific hake for 2009 was less certain. Several methods were explored to quantify the uncertainty and assess the reliability of the hake biomass estimate.