Kelp Forest Zooplankton, Forage Fishes, and Juvenile Salmonids of the Northeast Pacific Nearshore

Abstract

Kelp forests are an important ecological component of temperate coastal systems that are sensitive to anthropogenic disturbance and are in decline in many locations globally. In the northeastern Pacific Ocean off the coast of Washington, USA, bull kelp Nereocystis luetkeana forests are seasonally used by juvenile salmonids and forage fishes; however, details on ecosystem functional linkages for forage fishes and salmonids are not well quantified. Using a zooplankton drop net and snorkel surveys for fishes, we sampled two bull kelp forests across multiple years. Our goal was to quantify differences in the communities of zooplankton, juvenile salmonids (Chinook Salmon Oncorhynchus tshawytscha and Coho Salmon O. kisutch), and forage fishes (Pacific Herring Clupea pallasii, Surf Smelt Hypomesus pretiosus, and Pacific Sand Lance Ammodytes hexapterus) between kelp forests and adjacent nonkelp (open‐water) habitats. We tested the hypothesis that zooplankton common in the diets of surface‐oriented forage fishes and juvenile salmonids would be more abundant in kelp than in open water. At the overall assemblage level of organization, kelp and open‐water habitats had similarly abundant and diverse zooplankton communities. However, decapods and phytal‐associated harpacticoid copepods within this assemblage (i.e., groups that are an important component of fish diets) were significantly more abundant in kelp forests than in open‐water habitat. Greater presence and abundance of zooplankton, juvenile salmonids, and forage fishes in kelp forests compared to adjacent open‐water habitats suggest that kelp forests are important for culturally and economically valuable forage fishes and salmonids and warrant further study to define and conserve their ecosystem function.

Spatiotemporal Variation in Distribution, Size, and Relative Abundance within a Salish Sea Nearshore Forage Fish Community

“…2015; Shaffer et al. 2020). Intriguingly, the dominance of these three species is not reflected in beach seine collections in the central Strait of Juan de Fuca between 1976 and 1979 (Miller et al.…”

“…A number of forage fish species use nearshore ecosystems of the Salish Sea during portions of their life history, particularly as nursery habitat (Penttila 2007;Munsch et al 2016). Studies of forage fish use of these nearshore habitats have focused primarily on reproductive ecology and habitat associations (Penttila 2007;Haynes and Robinson 2011;Quinn et al 2012;Shaffer et al 2012Shaffer et al , 2020, especially for Pacific Herring, Pacific Sand Lance Ammodytes hexapterus, and Surf Smelt Hypomesus pretiosus. These three species are the most commonly occurring forage fish in this region (Emmett et al 1991;Penttila 2007;Greene et al 2015).…”

“…While broadly acknowledged, quantitative descriptions of within-year and interannual variation in forage fish assemblages in nearshore coastal habitats remain limited. In particular, researchers are building an understanding of spatial and temporal variability in the structure of these assemblages, as well as factors that may affect their distribution and abundance during residence in nearshore ecosystems (Weitkamp et al 2012;Munsch et al 2016;Shaffer et al 2020).…”

“…Most studies in nearshore areas have been short term (<3 years) in nature (Emmett et al 1991;Toft et al 2007;Quinn et al 2012;Rice et al 2012;Shaffer et al 2012). Longer-term data (>5 years) on forage fish use of nearshore ecosystems associated with shoreline areas show variable regional trends in forage fish catch over time and linkages between anthropogenic activities and forage fish abundance (Greene et al 2015;Shaffer et al 2020).…”

Toward a conceptual framework for managing and conserving marine habitats: A case study of kelp forests in the Salish Sea

“…Regardless of which functional groups make up a given kelp forest, the macroscopic stages create complex, three‐dimensional habitats that form the structural and energetic bases for an abundance of life (Teagle et al, 2017 ). Declines in kelp populations can therefore have large and cascading impacts on ecological and human communities (Graham, 2004 ; Shaffer et al, 2020 ).…”