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 4.5 4 3.5 Average Spr & Sum TP (ug/L) 3 2.5 2 1.5 1 0.5 0 1985 1995 2005 2015 Year Council of Lake Committees Meeting, Detroit, Michigan, October 15, 2018
The trophic transfer efficiency of the LH food web is low Average 9 % LH 12 % 6 % 15 % 3 % Trophic Transfer Efficiency 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 other 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 other species of interest 1981-85 1998-02 2006-2008 Other Salmonines Walleye Whitefish Burbot Lake Trout Chinook Round Goby Bloater Sculpin Yellow Perch Alewife Smelt 0 500 1000 1500 2000 2500 3000 3500 4000 PPR (g/m2) Council of Lake Committees Meeting, Detroit, Michigan, October 15, 2018
Increased water clarity is an additional ubiquitous influence but difficult to fully understand Fishery Fishery Assessment Fish Lower Trophic Community Levels Catchability/Vulnerability Habitat Change Distribution Feeding Behaviour 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 drawing Sunlight Edible Algae drawing drawing drawing drawing Mussels Large Predator Zooplankton Small Prey & Fish & Mysis Predator Fish drawing Bottom Fish, Organisms & Organic Matter Council of Lake Committees Meeting, Detroit, Michigan, October 15, 2018
Large Predator Fish TL-5 TL-4 Small Prey & Predator Fish TL-3 TL-2 Zooplankton & Mysis TL-1 Algae & Organic Matter Council of Lake Committees Meeting, Detroit, Michigan, October 15, 2018
Recommend
More recommend
