Multiple Limiting Factors and Restoration of a Brook Trout Metapopulation J. Todd Petty and Brock M. Huntsman Steve Brown (WVDNR), Paul Kinder (NRAC), TJ Burr (NRCS)
The Problem Extirpated from or highly reduced in over 50% of their native range. Exist as isolated, relict populations throughout much of the mid-atlantic. Acidification, harvest, warming, barriers, sedimentation, exotic species.
Shavers Fork near Cheat Bridge, WV 1927 - WV Magazine Big Rivers Big Fish Brook trout from Blackwater River, WV circa 1900-1920
The Process of Restoration Specific Restoration Actions Monitoring & Adaptation Restoration Plan Foundational Knowledge Limiting Factors Goals & Objectives Re-introduction Liming Stream Channel Restoration Riparian management Barrier Removal Harvest control Exotic Removal Petty, J. T. & Merriam, E. P. (2012) Brook Trout Restoration. Nature Education Knowledge 3(7):17
Shavers Fork Headwater Tributaries Larger Tributaries Mainstem
Foundational Knowledge Small tributaries represent source habitats within the Shavers Fork metapopulation. -> 80% all spawning occurs within streams < 3 km2 drainage area. -Spawning success is driven by acidification. -Food availability limits population size and individual growth. -Tributaries supply individuals to mainstem habitats (some more so than others).
Reproduction and recruitment is focused in small, alkaline streams (Petty et al. 2005. TAFS) 1 km 2 = 250 acres
Acidification of Headwaters 80% of spawning habitat has been lost as a result of acidification. And much remaining habitat is isolated above culverts. Petty and Thorne. 2005. Restoration Ecology Historic Current
28% 9% 19% 114% 51% 22% 4% 10% Gene Flow from tribs to mainstem
Important link between tributaries and mainstem sites
Foundational Knowledge Mainstems represent productive sink habitats. -No spawning occurs in the mainstem. -Inhabited by large, highly mobile individuals. -Used as both productive foraging habitat and as a corridor for dispersal among tributaries. -Mainstem populations are limited by the availability of thermal refugia.
Habitat Dependent Growth
Trout mobility and thermal refugia Petty et al. 2012. TAFS
Limited Thermal Refugia in MS Fewer but larger fish during hot years Mean adult SL (mm) 200 Mainstem 4 180 160 140 120 100 80 11.0 11.5 12.0 12.5 13.0 13.5 14.0 Mean April t -June t maximum temperature (ºC) Suggests superior fish controlling habitable microhabitat
6/1 6/8 6/15 6/22 6/29 7/6 7/13 7/20 7/27 8/3 8/10 8/17 8/24 8/31 Daily Feeding Hours Mainstem thermal regime 30 25 Number of Hours < 21 0 C 20 15 10 5 1999 2000 2001 Second Fork 0 Day
Restoration Plan Limiting Factor Action Effect Acidity Treatment of headwaters w limestone sand Increase spawning habitat and supply of brook trout from tribs to the mainstem Dispersal Barriers Replace culverts Increase links between source tribs and productive mainstem Thermal refugia Mainstem channel habitat enhancement Increase availability of thermal refugia increase carrying capacity during warm years.
Restoration Plan 1. Limestone Sand designed to maximize recovery of brook trout reproductive habitat LS 2. Culvert Replacement designed to link reproductive habitat in HW to foraging habitat in MS x LS LS 1. Natural Stream Channel Design designed to provide thermal refugia and foraging microhabitats and link Rocky Run to Second Fork. x x LS LS
Limestone sand treatment Start of Treatment
Upper Shavers Fork Watershed Beaver Creek Lamothe Hollow Oats Run
Lamothe Hollow Oats Run
Oats Run
Isotopes and assessing connectivity
Mainstem Restoration
Post-Restoration Pre-Restoration
Key Conclusions If populations are structured as metapopulations rather than fragmented isolates, then: 1.Dispersal matters as much or more than habitat quality. 2.Restoration actions in one area will affect populations in another. 3.Populations are likely limited by multiple factors operating over multiple locations.
Brook trout Channel Unit Use Predicted abundance 10 8 6 4 IGR IGRRC LGRGC SPC STRUCTURE 2 0 0 200 400 600 800 Distance from nearest Source (m)