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Open Access Publications from the University of California

Scholarly Works (2 results)

  • Thesis
  • Peer Reviewed
UC San Diego Electronic Theses and Dissertations (2017)

Most organisms shift between different ecological niches or habitats throughout their lives. These shifts are prompted by growth and changing resource needs. In the marine realm, understanding why and when fish shift habitats is particularly important due to the increasing use of spatial management as a conservation strategy. Effective spatial management requires understanding how a species habitat usage changes throughout its’ lifespan.

Within the Southern California Bight (SCB)Yellowtail (Seriola lalandi) are iconic gamefish and widely targeted throughout the region, both in U.S. and Mexican territorial waters. Their cross-border movements mean these fish encounter a diverse array of anthropogenic pressures, ranging from ocean-warming to agricultural and urban run-off to significant recreational, artisanal, and commercial fishing.

This work attempts to understand and quantify how yellowtail use the Southern California Bight and how that usage affects their biology. This was carried out in 3 separate chapters dealing with analysis of long-term recreational catch records, conventional tagging, passive acoustic telemetry as well as spatially-explicit analysis of age, growth, diet and trophic position.

The primary differences detected across all investigated parameters were size-mediated. Thus, one contiguous population with distinct ontogenetic shifts in habitat and diet is the most parsimonious explanation for the results from each chapter presented in this thesis. Recreational catch data showed inshore and offshore catch sizes were different between years and across seasons and fish size, rather than tagging season best explained detection rates of acoustically tagged fish. These findings supported claims by recreational anglers that large fish caught inshore are potentially year-round SCB residents. The conclusion of one, panmictic, SCB yellowtail population is further supported by results from life-history analysis as fish size again was the only source of significant differences in age/growth, diet, or trophic position regardless of sampling location or region.

Results from tag returns, acoustic telemetry and life-history analysis indicate that there is likely one contiguous population of yellowtail in the SCB and that due to high

levels of fishing pressure, this population may be reliant on seasonal influxes of fish from the south to sustain current fishing levels.

    Cover page: The Biology of Yellowtail (Seriola lalandi) in the Southern California Bight: Spatial Insights from Recreational Catch Records, Tagging and Life-History Characteristics.
    • Article
    • Peer Reviewed
    UC San Diego Previously Published Works (2023)
    The fisheries history of the Giant Sea Bass, Stereolepis gigas (Telostei: Polyprionidae), is closely linked to its spatial ecology. Its overharvest is directly associated with formation of spatially distinct spawning aggregations during summer, while its subsequent recovery is hypothesized to be the result of spatially explicit gear restrictions. Understanding the spatial ecology of Giant Sea Bass is a key part of efforts to assess contemporary threats such as commercial harvest and incidental catch by recreational fisheries. In this study, we used acoustic telemetry to characterize Giant Sea Bass space use in the La Jolla kelp forest using an acoustic array that encompasses two marine protected areas (MPAs) and heavily trafficked recreational fishing grounds. Five of the seven fish we tagged remained in the La Jolla array for at least 6 months. Two fish were resident across multiple years, with one fish consistently detected for 4 years. Only one fish was detected in the broader network of regional acoustic receivers, moving north approximately 8 km to Del Mar. Most tagged fish had home ranges and core use areas indicating they spend considerable time outside MPAs, particularly in areas with high recreational fishing activity. During spawning season we detected fish less frequently in the La Jolla array and recorded higher movement rates. While the current MPA network in La Jolla by no means offers complete protection to this fish, it does appear to support long-term persistence of some individuals in a region of exceptionally high recreational fishing pressure.
      Cover page: Spatial ecology of the Giant Sea Bass, Stereolepis gigas, in a southern California kelp forest as determined by acoustic telemetry.
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