Dataset: Larval fish observations, environmental data, and associated analysis code from 1995-2018 from Mexico, USA, and Canada

We collated larval fish density data in larvae/m3 from six long-term ichthyoplankton sampling programs covering the region between the southern part of the Baja California Peninsula to the Alaska Peninsula in the western Gulf of Alaska. These surveys were the National Oceanic and Atmospheric Administration (NOAA) Ecosystems and Fisheries Oceanography Coordinated Investigations (EcoFOCI), multiple compiled surveys organized by Fisheries & Oceans Canada, the NOAA Pre-recruit Survey, Newport Hydrographic Line, California Cooperative Oceanic Fisheries Investigations and the Investigaciones Mexicanas de la Corriente de California.

All surveys sampled to 100-200 m depth (or bottom depth, if shallower) with net meshes ranging between 200-505 μm. Only bongo nets or ring net tows within the 200 nm Exclusive Economic Zone were retained within this study. We examined years 1995-2018. Larvae from sixteen species from three adult habitat categories (coastal pelagics, groundfishes, and mesopelagics) were retained. All species were of interest for their importance in commercial or recreational fisheries, as forage fish, or due to high biomass. Species varied in their geographic spread, from regional to coastwide. For instance, of selected mesopelagics, Panama lightfish (Vinciguerria lucetia) and Mexican lampfish (Triphoturus mexicanus) are both restricted to southern California and the Baja Peninsula, while Northern lampfish (Stenobrachius leucopsarus) and blue lanternfish (Tarletonbeania crenularis) are abundant throughout the entire study domain.

The full datasets of the surveys compiled are available through the following locations/contacts (links in related datasets section):

- EcoFOCI: by request
- Department of Fisheries & Oceans Canada: by request (current contacts are R. Ian Perry or Moira Galbraith)
- NH-Line: by request
- Pre-Recruit Survey: by request
- CalCOFI: ERDDAP (Dataset ID:  erdCalCOFIlrvcnt)
- IMECOCAL: by request

Environmental data: For environmental variables, we used a hindcast developed with the Regional Ocean Modeling System (ROMS), configured for the eastern North Pacific at 10-km resolution and encompassing the period from 1995-2020. The model was forced with daily atmospheric fields from the ERA5 reanalysis produced by European Centre for Medium-Range Weather Forecasts (Hersbach et al. 2020) and open ocean boundary conditions from the 1/12° Global Ocean Reanalysis and Simulation (Lellouche et al. 2021) provided every five days. We extracted sea surface temperature (SST), sea surface salinity (SSS), sea surface height (SSH), and “spiciness” from ROMS data. Spiciness combines salinity and temperature and is an indicator of water mass changes. We additionally extracted bottom depth using R package marmap (Flament 2002). SST, SSS, and SSH were surface values, which is appropriate given the near-surface distribution for most fish larvae. Spiciness was averaged over the upper 250 m of the water column, approximately corresponding to the deepest depth that nets reached across all programs. Each empirical tow was matched to ROMS data using bilinear interpolation. ROMS data is available by request from Jerome Fiechter (fiechter@ucsc.edu).