Spatiotemporal patterns of variability in the abundance and distribution of winter-spawned pelagic juvenile rockfish in the California Current

Abstract

Rockfish are an important component of West Coast fisheries and California Current food webs, and recruitment (cohort strength) for rockfish populations has long been characterized as highly variable for most studied populations. Research efforts and fisheries surveys have long sought to provide greater insights on both the environmental drivers, and the fisheries and ecosystem consequences, of this variability. Here, variability in the temporal and spatial abundance and distribution patterns of young-of-the-year (YOY) rockfishes are described based on midwater trawl surveys conducted throughout the coastal waters of California Current between 2001 and 2019. Results confirm that the abundance of winter-spawning rockfish taxa in particular is highly variable over space and time. Although there is considerable spatial coherence in these relative abundance patterns, there are many years in which abundance patterns are very heterogeneous over the scale of the California Current. Results also confirm that the high abundance levels of YOY rockfish observed during the 2014–2016 large marine heatwave were largely coastwide events. Species association patterns of pelagic YOY for over 20 rockfish taxa in space and time are also described. The overall results will help inform future fisheries-independent surveys, and will improve future indices of recruitment strength used to inform stock assessment models and marine ecosystem status reports.

Recruitment variability and sampling design interact to influence the detectability of protected area effects

“…Finally, if there are large environmental differences between reserves and fished areas (e.g., for kelp bass, kelp availability is important in survival of young‐of‐years; White & Caselle, 2008), then detectability is also likely to be lower than we found, and sampling designs that explicitly account for habitat should be considered (Miller & Russ, 2014). This may also be the case when comparing sites across large spatial scales, which can exhibit high variability in recruits of the same species (e.g., rockfish across the California current; Field et al, 2021). In our study, we also focused on the case where adults are relatively sedentary and do not move across reserve boundaries.…”

“…An important difficulty is that most conventional fishery management models assume that recruitment is determined by the size of the spawning adult population, so harvest rates can be adjusted to ensure sufficient recruitment for sustainability. Yet, in many stocks, recruitment is not correlated with spawning output (at least over the observed range of stock sizes, particularly for well‐managed stocks); rather, recruitment varies stochastically and spawning stock abundance is set by the series of recruitment events in prior years (Field et al, 2021; Szuwalski et al, 2015). Thus variability in recruitment will translate into variability in the stock itself, making it difficult to detect deterministic changes in the stock in response to management.…”

“…Thus variability in recruitment will translate into variability in the stock itself, making it difficult to detect deterministic changes in the stock in response to management. In the case of spatial management, the strength and magnitude of recruitment can vary greatly year‐to‐year even in regions where there are consistent spatial patterns of propagule supply (e.g., Caselle et al 2010; Field et al, 2021; Hamilton et al, 2006; Shanks & Roegner, 2007; Wheeler et al, 2017). This variation has important consequences for metapopulation dynamics (Siegel et al, 2008), and by extension the response of populations to spatial management actions (Harrison et al, 2020).…”

Fisheries Surveys Are Essential Ocean Observing Programs in a Time of Global Change: A Synthesis of Oceanographic and Ecological Data From U.S. West Coast Fisheries Surveys

“…Since 2001, the NWFSC has conducted a comparable survey in the Pacific Northwest off Oregon and Washington, first as a collaborative effort with the Pacific Whiting Conservation Cooperative (2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009) and more recently with NOAA research vessels (2011-present), using complementary methods (see the section "National Oceanic and Atmospheric Administration Coastal Cooperative Pre-recruit Survey" below). Data from both the SWFSC and NWFSC surveys are pooled to develop indices of juvenile rockfish abundance to support stock assessments (Field et al, 2021) as well as to support other ecosystem investigations.…”

“…Since 2011, it has been operated by the NWFSC and coordinates directly with the RREAS (Brodeur et al, 2019a). Data from these two surveys are pooled to support indices for stock assessments and other investigations (e.g., Friedman et al, 2018;Field et al, 2021). PRS sampling occurs annually in May-July during seasonal ocean upwelling and increased southward transport.…”