Fish Conservation and Management

Transcription

1 Fish Conservation and Management CONS 486 Managing biotic communities Gardening, poisoning, and shocking what would PETA think? Chapter 10 Ross

2 Managing biotic communities Topics Organism additions Organism control/elimination

3 Major theme: Linking science to conservation & management Physiology Behaviour Population ecology Ecosystem ecology Habitat data (limnology, oceanography) Life history Basic science Applied science Fisheries exploitation data Applied life history data Human dimensions: socioeconomic data Protecting populations & habitats Restoring populations & habitats Conservation Management Harvest regulations Managing fisheries & habitats

4 Managing biotic communities: Background Three common manipulation types: 1. Addition of animals to provide a forage base for fish populations supporting fisheries 2. Elimination of undesirable fish 3. Reduction of dense weed beds (discussed this last lecture)

5 Managing biotic communities: Addition of animals Forage Introductions To be successful, forage introductions must: 1. Provide an abundant food supply 2. Not experience wide fluctuations in abundance 3. Effectively transfer primary production to higher trophic levels 4. Be vulnerable to predation based on their size, behaviour, habitat preferences 5. Be innocuous (no negative community effects) Very few ever meet these criteria must consider when evaluating introductions

6 Organism additions: invertebrate introductions E.g. Opposum shrimp (Mysis relecta) a glacial relict marine species native to oligotrophic lakes in eastern north America They feed on smaller zooplankton Mysis relicta (Opposum shrimp) ~ 3 cm length

7 Naturally occurring zooplankton - Crustaceans (~ 4 mm length) - prey for Mysis shrimp Cladocerans ( water fleas ) Copepods

8 Organism additions: invertebrate introductions Kootenay Lake: after initial stocking, growth and size at maturity of kokanee increased Mysis were stocked into lakes across western North America Mysis populations started to do well at the expense of the native zooplankton that it ate Less zooplankton for kokanee! Mysis vertically migrate to lake bottoms during the day and rise at night Minimizing contact with visual feeding zooplanktivorous fish (e.g. kokanee) Behaviourally avoid predation!

9 US introductions of Mysis

10 Spencer et al BioScience

11 Spencer et al BioScience

12 Organism additions: invertebrate introductions Abundances of lake trout and bull trout have declined or crashed in most lakes where Mysis were introduced Because their forage food (juvenile kokanee) declined

13 Organism additions: invertebrate introductions Conclusions: Why was shrimp not a good choice for introduction? Provide an abundant food supply? Not experience wide fluctuations in abundance? Effectively transfer primary production to higher trophic levels? Be vulnerable to predation based on their size, behaviour, habitat preferences? Be innocuous (no negative community effects)? Seems to only be effective in shallow lakes where shrimp cannot easily hide in deep water

14 Organism additions: fish introductions inconsistent results shad (pelagic prey) have been introduced into many reservoirs, but they can get bigger than their predators (walleye, striped bass) so biomass gets locked into shad not transferred to sport fish smelt and alewife (pelagic prey) introduced into eastern NA lakes but their numbers fluctuate wildly and at certain abundances can compete with desired recreational fishes

15 Organism additions: fish introductions One of few fish forage introduction success stories seems to be with the introduction of kokanee into western lakes where they provide stable food for larger body lake trout/bull trout kokanee can effectively forage on zooplankton, stay small, and spawn in stable streams so have good (not boom/bust) recruitment bottom line difficult to introduce an organism that won t generate unforeseen interactions

16 Organism Elimination How do you control/eliminate undesirable fish? Seines, nets, traps, weirs, electrofishing, water level manipulations never 100% effective, need to do this regularly, on-going actions Toxicants best way to remove fish but they have problems e.g. Rotenone, a plant extract, most common non-specific fish toxicant blocks oxygen uptake; detoxifies in just a couple days problems: repels fish without killing them, doesn t kill eggs, kills other gill breathers (moderately toxic to humans)

17 killing a lake using rotenone to eliminate the fish community

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19 Eliminating carp: carcass recovery

20 Unintentional fish introductions: Prevention is key!

21 Special Undesirable Species Northern Pikeminnow family cyprinidae A very big minnow (30-60 cm total length) Deemed so undesirable that $millions have been spent to try to eradicate them Pikeminnow prey on migrating salmon Large scale removal programs in Pacific NW Toxicants, explosives, traps, bounties all used

22 Northern pikeminnow Recreational reward fishery (WA/OR) Anglers paid to remove larger size class pikeminnow that prey on salmon Annual budget has varied from $2.0 to $6.4 million, with an average of about $3.0 million Goal to obtain 10% exploitation rate on larger size class pikeminnow Usually meet this target! Goal not to eliminate, but to control the size classes that prey on juvenile salmon

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24 Sea Lamprey Special Undesirable Species Invaded Great Lakes through the canal and lock system in 1800s Contribute to decline of lake trout Parasitic

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26 Lamprey problem led to creation of the International Great Lakes Fishery Commission Bi-national organization established to manage fisheries in the Great Lakes $Billions spent on R&D Unique lampricide kills benthic larvae Applied yearly and only effective in small streams Goal to control abundance but will never eliminate

27 Control strategies: lampricides, traps, low-head barriers, pheromones

28 Some success!

29 But lampreys have recently rebounded The present hot zone is the St. Marys River Migrate from St Marys into Lake Huron and northern Lake Michigan There, the adult sea lamprey population is nearly as large as it was 40 years ago (before control measures!) when lake trout and whitefish stocks were decimated

30 Special Undesirable Species The Asian Invasion: carp make a splash Asian carp (Hypophthalmichthy spp.) species have spread across the central US and are at risk of establishing in the Great Lakes Extremely rapid colonization throughout Mississippi They ve only been around since the 70s! Out-compete native species due to rapid growth and reproduction Now one of the most abundant species in its range

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32 REPORTED - Not necessarily seen or captured but may have positive edna results from water body

33 Keeping carp out of the Great Lakes Electric barrier excludes carp from Lake Michigan

34 If the electric fence fails, this might be the future of Great Lakes Fisheries????