Type of Presentation

Oral

Session Title

The Salish Sea Marine Survival Project- Novel Approaches, Project Status and Key Findings

Description

The existence, causes and potential consequences of widespread increases in ‘jellyfish’ (ctenophores, medusae and salps) abundance are hotly debated topics in marine ecology. Jellyfish have often been considered trophic dead ends; consuming zooplankton and making it inaccessible to higher trophic levels. We investigated the possibility that a hyperiid amphipod (Hyperia medusarum) acts as a trophic linkage between a large scyphozoan jellyfish (Phacellophora camtschatica) and Chinook Salmon (Onchorhyncus tshawytscha) in the Salish Sea. Hyperia medusarum was a significant food source for juvenile Chinook Salmon in the Southern Gulf Islands in the summers of 2014 and 2015. Nematocysts were present in the foreguts of both amphipods parasitizing jellyfish and amphipods from juvenile Chinook Salmon stomachs, suggesting energy flow from the jellyfish to the salmon through the amphipods. Size frequencies and sex ratios differed significantly for amphipods obtained directly from jellyfish and those from Chinook Salmon stomachs, with salmon feeding primarily on large, female Hyperia. Juvenile Chinook Salmon may be preferentially picking female amphipods directly off medusae or preying on them during a life history event in which they leave their host. We discuss our results in the context of recent increases in the abundance of P. camtschatica in the Salish Sea (beginning early 1990s), and literature data that suggest hyperiid amphipods are becoming more prevalent in the diets of juvenile salmon in the Salish Sea and beyond.

Comments

This work is linked to a juvenile Chinook Salmon ecology project funded in part through the SSMSP. We have discussed this submission with Isobel Pearsall and she recommends that it be included as a 5 minute talk in an SSMSP session.

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Evidence that a hyperiid amphipod trophically links large scyphozoan jellyfish to Chinook Salmon in the Salish Sea

2016SSEC

The existence, causes and potential consequences of widespread increases in ‘jellyfish’ (ctenophores, medusae and salps) abundance are hotly debated topics in marine ecology. Jellyfish have often been considered trophic dead ends; consuming zooplankton and making it inaccessible to higher trophic levels. We investigated the possibility that a hyperiid amphipod (Hyperia medusarum) acts as a trophic linkage between a large scyphozoan jellyfish (Phacellophora camtschatica) and Chinook Salmon (Onchorhyncus tshawytscha) in the Salish Sea. Hyperia medusarum was a significant food source for juvenile Chinook Salmon in the Southern Gulf Islands in the summers of 2014 and 2015. Nematocysts were present in the foreguts of both amphipods parasitizing jellyfish and amphipods from juvenile Chinook Salmon stomachs, suggesting energy flow from the jellyfish to the salmon through the amphipods. Size frequencies and sex ratios differed significantly for amphipods obtained directly from jellyfish and those from Chinook Salmon stomachs, with salmon feeding primarily on large, female Hyperia. Juvenile Chinook Salmon may be preferentially picking female amphipods directly off medusae or preying on them during a life history event in which they leave their host. We discuss our results in the context of recent increases in the abundance of P. camtschatica in the Salish Sea (beginning early 1990s), and literature data that suggest hyperiid amphipods are becoming more prevalent in the diets of juvenile salmon in the Salish Sea and beyond.