Groundfish predation on diadromous fish in the Gulf of Maine

Groundfish predation on diadromous fish in

the Gulf of Maine Christine Lipsky1, Brian Smith2, Stacy Rowe2,

Tim Sheehan2, and Michael O’Malley3

1NOAA Fisheries Service, NEFSC, Orono, Maine 2NOAA Fisheries Service, NEFSC, Woods Hole, Massachusetts

3Marine Scotland, Aberdeen, UK

Northeast Fisheries Science Center

Atlantic Salmon Ecosystems ForumJanuary 8, 2014University of Maine, Orono, Maine

Presentation Outline• Introduction/Background• Objectives• Methods • Results • Revisit objectives• Next steps

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Introduction/Background• Kennebec River• Two dams removed in the past 15 years• Two million river herring counted in

2013• Penobscot River • Two dams removed in past two years,

another to be breached• “Operational Plan for the Restoration of

Diadromous Fishes to the Penobscot River” – stocking plan

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• Diadromous fish may have been an important prey source for Atlantic cod (Gadus morhua) and other groundfish

• The decline in diadromous fish populations adversely affected marine predator populations (Baird 1883; Ames 2004)

• Restoring coastal predator populations would require the reestablishment of a large varied forage base (which would include diadromous fish) (Hall et al., 2012)

Introduction/Background

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1. Examine NEFSC Food Habits Database (FHDB) for presence of diadromous fish in the stomachs of groundfish predators

2. Conduct survey to quantify presence of diadromous fish in the stomachs of groundfish from nearshore areas adjacent to the Kennebec and Penobscot Rivers

3. Compare results from Kennebec and Penobscot, before and after restoration

Project Objectives

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Methods—Areas of Interest

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-72 -71 -70 -69 -68 -67 -66 -65

41

42

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Kennebec Region

Penobscot Region

Degrees West

Degr

ees

North

Methods• Use nearshore trawling platforms to sample fish in

2010 and 2011Maine DMR Inshore Trawl NEFSC R/V Gloria Michelle

• Target times when diadromous fish are suspected to be in the area—spring, late summer/early fall

• Target known predators of diadromous fish (from FHDB)

• Focus on predators >20 cm

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Methods—Targeted Species

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credit: theguardian.com

Atlantic cod

credit: Joyce Photographics

spiny dogfish

credit: Donald Flescher, NEFSC/NOAA

silver hake

credit: thejump.net

sea raven

credit: Donald Flescher, NEFSC/NOAA

thorny skatecredit: Marine Creations Taxidermy

goosefish

winter skate

credit: Joe Kunkel, UMass

• Non-empty stomachs collected: 1,128– Stomachs containing diadromous fishes: 17– Alewife and blueback herring were the only

diadromous species definitively IDed • Diadromous fish less prevalent in diets than Atlantic

herring (which are generally more abundant in the sampled area), but…

• More diadromous fish found in stomachs of fish offshore of mouth of Kennebec than mouth of Penobscot River

Results—2010 and 2011 (Bransome et al., in review)

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Results—2010 and 2011 (Bransome et al., in review)

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Start positions of Diadromous Sampling Project tows.

Results—2010 and 2011 (Bransome et al., in review)

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Start positions of tows with alosines as prey by season.

Kennebec Region

Results—2010 and 2011 (Bransome et al., in review)

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Table 1. Percent diet by weight of alosines.

SP 10 SU 10 FA 10 SP 11

Spiny dogfish 4.37 8.38 Cod 11.19 10.56 Silver Hake 4.93 Goosefish 3.49 6.05 1.42 Sea Raven 2.14

• More diadromous fish were found in stomachs of predators in nearshore areas than offshore

• A difference in the contribution of diadromous fishes to the diets of predators in nearshore areas adjacent to the Kennebec and Penobscot Rivers is suspected although additional sampling is necessary

Summary

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1. Examine NEFSC Food Habits Database (FHDB) for presence of diadromous fish in the stomachs of groundfish predators

2. Conduct survey to quantify presence of diadromous fish in the stomachs of groundfish from nearshore areas adjacent to the Kennebec and Penobscot Rivers

3. Compare results from Kennebec and Penobscot, before and after restoration

Objectives

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Next Steps• Samples were collected in 2012 and 2013 in spring

and fall using DMR trawl surveys, and plans are to continue sampling in 2014 and beyond

• Samples from spring and fall DMR trawl surveys in 2012 have been processed; data will be analyzed after 2013 and 2014 samples are collected and processed

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Next Steps• Continue to quantify contributions of diadromous

prey to the diets of commercially-important species• Monitor the interaction between diadromous fish

and their predators in the context of restoration and dam removal

Acknowledgements• Keri Stepanek, MDMR • Sally Sherman, MDMR• Justin Stevens, NOAA• Julie Nieland, NOAA

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