The In Influence of Lower Trophic ic Levels on Fis isherie ies: - - PowerPoint PPT Presentation

The In Influence of Lower Trophic ic Levels on Fis isherie ies: Possible Ele lements of a Fact Sheet

Tom Stewart

Council of Lake Committees Meeting, Detroit, Michigan, October 15, 2018

Background

At the spring CLC meeting a conceptual model of fisheries management implications of LTL changes was presented and discussed by CLC Follow-up was to bring to the fall CLC meeting a prototype fact sheet using Lake Huron as an example.

Council of Lake Committees Meeting, Detroit, Michigan, October 15, 2018

Objectives

• Review the fact sheet in your

briefing book

• Discussion
• Issues
• Audience for fact sheet
• Content and format
• Next steps & process

Council of Lake Committees Meeting, Detroit, Michigan, October 15, 2018

Key Ele lements

• Phosphorus declines in LH are reducing total

fish biomass potential

• The trophic transfer efficiency of the LH food

web is low

• The food web has been disrupted and primary

production is not getting effectively channeled to top predators and other species of interest

• Increased water clarity is an additional

ubiquitous influence but difficult to fully understand

Council of Lake Committees Meeting, Detroit, Michigan, October 15, 2018

Phosphorus declines in LH are reducing total fish biomass potential

0.5 1 1.5 2 2.5 3 3.5 4 4.5 1985 1995 2005 2015 Average Spr & Sum TP (ug/L) Year Council of Lake Committees Meeting, Detroit, Michigan, October 15, 2018

15 % 3 % 12 % 9 % 6 % LH Average

Trophic Transfer Efficiency

The trophic transfer efficiency of the LH food web is low

Council of Lake Committees Meeting, Detroit, Michigan, October 15, 2018

The food web has been disrupted and primary production is not getting effectively channeled to top predators and

• ther species of interest

Council of Lake Committees Meeting, Detroit, Michigan, October 15, 2018

The food web has been disrupted and primary production is not getting effectively channeled to top predators and

• ther species of interest

500 1000 1500 2000 2500 3000 3500 4000 Smelt Alewife Yellow Perch Sculpin Bloater Round Goby Chinook Lake Trout Burbot Whitefish Walleye Other Salmonines PPR (g/m2)

1998-02 2006-2008 1981-85

Council of Lake Committees Meeting, Detroit, Michigan, October 15, 2018

Increased water clarity is an additional ubiquitous influence but difficult to fully understand

Catchability/Vulnerability Habitat Change Distribution Feeding Behaviour

Lower Trophic Levels Fish Community Fishery Assessment Fishery

Council of Lake Committees Meeting, Detroit, Michigan, October 15, 2018

Fisheries managers can influence future outcomes How?

(LH Committee, Partners & Stakeholders)

• Manage to re-establish a prey fish

base

• Manage fisheries more

conservatively

• Stock fish more conservatively
• Maintain critical fish habitat
• Educate stakeholders (change

expectations)

• Maintain sea lamprey control

Council of Lake Committees Meeting, Detroit, Michigan, October 15, 2018

Dis iscussion

• Issues
• Audience for fact sheet
• Content and format
• Next steps & process

Council of Lake Committees Meeting, Detroit, Michigan, October 15, 2018

Hip Pocket Slides

Council of Lake Committees Meeting, Detroit, Michigan, October 15, 2018

Nutrients Sunlight

Edible Algae

drawing

Large Predator Fish

drawing

Zooplankton & Mysis

drawing

Bottom Fish, Organisms & Organic Matter

drawing

Small Prey & Predator Fish

drawing

Mussels

drawing

Council of Lake Committees Meeting, Detroit, Michigan, October 15, 2018

Algae & Organic Matter Zooplankton & Mysis Small Prey & Predator Fish Large Predator Fish

TL-1 TL-2 TL-3 TL-4 TL-5

Council of Lake Committees Meeting, Detroit, Michigan, October 15, 2018