Presentation Abstract

Bull kelp (Nereocystis luetkeana) is an important source of both habitat and primary production in the Salish Sea and appears to be in decline in certain areas. Northern Kelp Crabs (Pugettia producta) are large crustacean consumers that preferentially consume N. luetkeana over other local seaweed species in laboratory feeding trials and exert some level of top-down control on kelp populations in the field. We have observed differences in kelp crab density around the Salish Sea and noted P. producta living on invasive wireweed (Sargassum muticum) as well as on kelp and in other habitats. We used a combination of laboratory feeding assays, field surveys, and crab foregut dissection to help quantify P. producta feeding preferences and determine if kelp crab gut contents “match” the substrate from which they were collected. Whole tissue laboratory feeding trials indicated the kelp crabs prefer to eat bull kelp; however, when offered artificial food (“algal jello”), crabs can and do eat Sargassum. The gut contents of crabs collected near San Juan Island contained sometimes very high levels of Sargassum, while crabs collected further south (Squaxin Island, Joemma State Park) contained less Sargassum even though it was still present in the environment. Crab foreguts were sometime filled with diatoms, ulvoid algae, and even eelgrass blades, indicating that they may be opportunistic feeders in the field. A better understanding of the ecological relevance of Northern Kelp Crab feeding preferences has important implications for future bull kelp management, conservation, and restoration efforts.

Session Title

Session 2.2A: Kelp: Stressors, Trends, and Value (Part II)

Conference Track

Kelp & Seagrass

Conference Name

Salish Sea Ecosystem Conference (2020 : Online)

Document Type

Event

SSEC Identifier

2020_abstractID_1272

Start Date

22-4-2020 12:30 PM

End Date

22-4-2020 2:00 PM

Geographic Coverage

Salish Sea (B.C. and Wash.)

Rights

Copying of this document in whole or in part is allowable only for scholarly purposes. It is understood, however, that any copying or publication of this document for commercial purposes, or for financial gain, shall not be allowed without the author's written permission.

Language

English

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Apr 22nd, 12:30 PM Apr 22nd, 2:00 PM

Northern kelp crab (Pugettia producta) feeding preferences - kelp crabs eat kelp, and lots else?

Bull kelp (Nereocystis luetkeana) is an important source of both habitat and primary production in the Salish Sea and appears to be in decline in certain areas. Northern Kelp Crabs (Pugettia producta) are large crustacean consumers that preferentially consume N. luetkeana over other local seaweed species in laboratory feeding trials and exert some level of top-down control on kelp populations in the field. We have observed differences in kelp crab density around the Salish Sea and noted P. producta living on invasive wireweed (Sargassum muticum) as well as on kelp and in other habitats. We used a combination of laboratory feeding assays, field surveys, and crab foregut dissection to help quantify P. producta feeding preferences and determine if kelp crab gut contents “match” the substrate from which they were collected. Whole tissue laboratory feeding trials indicated the kelp crabs prefer to eat bull kelp; however, when offered artificial food (“algal jello”), crabs can and do eat Sargassum. The gut contents of crabs collected near San Juan Island contained sometimes very high levels of Sargassum, while crabs collected further south (Squaxin Island, Joemma State Park) contained less Sargassum even though it was still present in the environment. Crab foreguts were sometime filled with diatoms, ulvoid algae, and even eelgrass blades, indicating that they may be opportunistic feeders in the field. A better understanding of the ecological relevance of Northern Kelp Crab feeding preferences has important implications for future bull kelp management, conservation, and restoration efforts.