Graduation Date

Spring 2022

Document Type

Thesis

Program

Master of Science degree with a major in Natural Resources, option Fisheries

Committee Chair Name

Jose Marin Jarrin

Committee Chair Affiliation

HSU Faculty or Staff

Second Committee Member Name

Helen Mulligan

Second Committee Member Affiliation

HSU Faculty or Staff

Third Committee Member Name

Tim Mulligan

Third Committee Member Affiliation

HSU Faculty or Staff

Fourth Committee Member Name

Andre Buchheister

Fourth Committee Member Affiliation

HSU Faculty or Staff

Subject Categories

Fisheries

Abstract

Historically written off as dull and homogenous, the dynamics of the sandy beach surf zone remains under studied world-wide. Northern California has been no exception to this global standard, as the sandy beach surf zone ecosystem in this region has yet to be characterized, and the effect of Marine Protected Areas (MPAs) on the fish and macroinvertebrate community fully ascertained.

Considered data-poor by local wildlife officials, commercially, recreationally and culturally important Amphistichus rhodoterus (redtail surfperch) and common Hyperprosopon ellipticum (silver surfperch) utilize the sandy beach surf zone in Northern California. Little is known about the effect of various environmental factors, or the effect of MPAs on these species. While the trophodynamics of redtail surfperch in this region have been researched, the diet of smaller individuals of this species and of silver surfperch have yet to be explored.

This thesis sought to enrich global knowledge of the sandy beach surf zone fish and invertebrate community by sampling four MPAs and four matched reference sites between San Francisco Bay and the California/Oregon border during the summers of 2019 and 2020. Data were gathered on the community by deploying baited remote underwater video cameras (BRUVs), seining, and collecting data on water and physical beach variables.

To better understand the effect of MPAs on silver and redtail surfperch a hook and line survey was conducted at two MPAs and two reference sites in Humboldt County during the summer of 2020. A diet analysis on silver and redtail surfperch in Humboldt County was also performed to gain information about the trophodynamics of these important species, and to provide further insight into the ecology of the sandy beach surf zone ecosystem.

Twenty-four taxa categories were identified on the underwater BRUV (Baited Remote Underwater Video) cameras such as Triakas semifasciata (leopard shark), Amphistichus spp. (surfperch genus) and Cancer spp (crab family), and 23 species from 12 families were identified in the seine sampling including redtail and silver surfperch, and Leptocottus armatus (pacific staghorn sculpin). The difference in community composition, species richness, and abundance between Drake’s and Doran, the southern-most paired-sites and the rest of the beaches was the clearest result. The study found no differences between years, and little effect of MPAs on the sandy beach surf zone fish and invertebrate community in Northern California. Water temperature (+), salinity (+), and total dissolved solids (-) were correlated with species richness and abundance in the BRUV data, while wave height (-) and salinity (+) were correlated with species richness and abundance in the seine data. Twenty-eight invertebrate diet taxa were observed in the stomachs of 51 redtail and 37 silver surfperch. This study found that silver surfperch have a more heterogenous diet than redtail surfperch, which may be influenced by wave height and water temperature. No significant difference in redtail surfperch length or catch per unit of effort (CPUE) between MPAs and reference sites in Humboldt County was found.

This study shows that like in other parts of the world, sandy beach surf zones are inhabited by a diverse fish and macroinvertebrate community that feeds on the smaller and diverse invertebrate community. The fish and macroinvertebrate community varied spatially among beaches, with Drake’s and Doran beaches having a significantly different community than the northernmost beaches. The MPAs showed little to no effect on the fish community, or the surfperch abundance and length, potentially because of the age of the MPAs, lack of enforcement, or minimal fishing pressure outside the MPA boundaries.

Few studies on the sandy beach surf zone have implemented both seining and baited remote underwater videos. It was found in this study that by employing these two sampling techniques a more complete picture of the sandy beach surf zone was able to be ascertained. Organisms which would not have been enumerated with seining alone due to their size or ability to escape the net, such as leopard sharks and Lontra canadensis (river otter), were able to be “captured” on video footage. Future research in the sandy beach surf zone habitat would benefit from this more robust sampling protocol, although if utilized in more energetic environments, modifications to the equipment are strongly suggested.

The purpose of this study was to (1) characterize the fish community in the sandy beach surf zone habitat in Northern California by quantifying the species richness, abundance and composition of species present, and relating these biotic metrics to environmental variables; (2) evaluate the effectiveness of the MPAs that include sandy beach surf zones of northern California by comparing the fish community within and outside MPA boundaries; (3) explore the effect of MPAs on length and CPUE of redtail surfperch in Humboldt County; and (4) analyze the diet composition of silver and redtail surfperch in the Northern California region.

The research presented in this thesis can help better inform fisheries management decisions in Northern California by providing insight into how various spatial, temporal, and environmental factors influence the sandy beach surf zone ecosystem and the trophodynamics of two important fish species, which inhabit this environment. A more complete understanding of the sensitivity of the sandy beach surf zone ecosystem to the factors researched in this thesis can promote knowledge surrounding the effect of large-scale shifts in the environment, and help direct management decisions to benefit future fisheries.

Citation Style

APA

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