Fish and Wild Exam 2

What are the 3 components of a fishery?

Aquatic organisms (fish), the environment (habitat), and humans (users)

3 key differences between fisheries management and wildlife management?

1. Fisheries rely heavily on stocking (no real wildlife equivalent)

2. More widespread introduction of nonnative species

3. Large commercial food production role (global protein source)

What drove the establishment of Fish Commissions in North America?

Declines in fish populations, overharvest, and the need to maintain fisheries for food and recreation.

Why were nonnative fish introductions (especially in the western US) popular?

To improve fishing, increase economic value, and keep waters “well stocked.”

Examples of nonnative fish introductions (species + origin)?

1. American shad → Atlantic to Pacific

2. Brown trout → Europe

3. Brook trout → Eastern North America

4. Rainbow trout → Western North America (moved widely)

Why have hatcheries been used so extensively in fisheries? Why not wildlife?

• Fish are easy to culture and have high reproductive rates

• Wildlife is harder to breed, raise, and release successfully

Hatcheries vs aquaculture?

• Hatchery: raise fish to release into the wild

• Aquaculture: raise fish for their entire life to sell as food

What values do fisheries management aim to maintain/enhance?

Economic, ecological, and cultural values

What are some values of recreational fisheries?

• Economic (tourism, jobs)

• Social/cultural (tradition, enjoyment)

• Personal (recreation, relaxation)

Example of how a species’ value has changed over time?

Bull trout: once considered undesirable and targeted (bounties), now protected and valued ecologically.

Main sources of funding for state fisheries agencies?

Fishing licenses + Dingell-Johnson/Wallop-Breaux (DJ/WB) excise taxes (not general state taxes).

What two factors determine DJ/WB funding allocation?

State size (area) and number of fishing licenses sold.

What % of fisheries funding in Montana comes from licenses vs DJ/WB?

DJ/WB = ~40–75% of budget; licenses make up most of the remaining funding.

4 major federal laws from ~1970s affecting fisheries?

• Clean Water Act

• Endangered Species Act

• National Environmental Policy Act (NEPA)

• Magnuson-Stevens Act

USFWS (U.S. Fish and Wildlife Service) role?

Manages threatened & endangered freshwater species and conducts environmental reviews.

NOAA Fisheries (National Marine Fisheries Service) role?

Manages marine/anadromous species and sets commercial harvest limits.

US Forest Service (USFS) role?

Manages fish habitat on forest lands (timber, grazing) and protects native species.

Bureau of Land Management (BLM) role?

Manages habitat and land use (grazing, mining) affecting fisheries.

Bureau of Reclamation role?

Builds/operates dams and irrigation systems (affects flow, habitat, fish passage).

Army Corps of Engineers role?

Builds dams, controls floods, alters rivers, and issues permits for stream modifications.

FERC (Federal Energy Regulatory Commission) role?

Licenses hydropower dams and requires mitigation for fish impacts during relicensing.

Key features of the Magnuson-Stevens Act (1976)?

Established U.S. Exclusive Economic Zone (3–200 miles)

Created 8 regional management councils

Uses Maximum Sustainable Yield (MSY) for management

Key updates to Magnuson-Stevens Act?

• 1996: Defined overfishing, required rebuilding plans

• 2006: Set annual catch limits (ACLs), strengthened science

Name 5 key federal agencies involved in fisheries management

USFWS, NOAA Fisheries, USFS, BLM, Army Corps of Engineers

What is maximum sustainable yield (MSY)?

The largest average catch that can be taken from a population indefinitely under average conditions.

What are biological reference points?

Benchmarks used to assess stock status and guide management decisions.

B (biomass)?

Total weight of fish in a stock.

F (fishing mortality)?

Rate at which fish are removed by fishing.

B₀?

Biomass before fishing (≈ carrying capacity, K).

BMSY?

Biomass that produces maximum sustainable yield.

FMSY?

Fishing mortality rate that produces MSY.

What is a stock-recruitment (SR) curve?

Relationship between adult stock size and number of new recruits.

What is surplus production?

Extra biomass produced beyond replacement (growth + reproduction available for harvest).

How is MSY found from an SR curve?

At the stock size where surplus production is maximized (peak difference between recruitment and replacement).

How does MSY relate to the logistic model?

MSY occurs at ~½ carrying capacity (K/2), where population growth is highest.

What is overfishing?

Fishing too hard (F > FMSY).

What is overfished?

Population biomass too low (B < BMSY).

What aspects of species ecology affect surplus production?

Growth rate, age at maturity, lifespan, fecundity.

How does the environment affect surplus production?

Conditions like food, temperature, and habitat quality change productivity.

Larkin criticism: “Catch all the big ones”?

Removing large fish reduces reproduction (big females produce more eggs).

Larkin criticism: Depensation?

At low population sizes, productivity declines → MSY assumptions fail.

Larkin criticism: Mixed-stock fisheries?

Harvesting multiple stocks can overfish weaker populations.

Larkin criticism: MSY ≠ MEY?

Maximum biological yield is not the same as maximum economic benefit.

What are 3 types of overfishing?

• Recruitment overfishing

• Growth overfishing

• Ecosystem overfishing

Why are commercial fisheries important?

They provide food (protein), jobs, and support global economies.

How have fisheries affected biodiversity (Worm et al. 2006)?

Large declines in marine biodiversity, with many stocks depleted or collapsed.

What is “fishing down marine food webs”?

Harvest shifts from large top predators to smaller, lower trophic species over time.

Two challenges to “fishing down marine food webs”?

• Changes may reflect market/target shifts, not depletion

• Spatial/temporal data bias can misrepresent trends

Why does catch not equal abundance?

Technology, effort, and efficiency can keep catch high even when populations decline.

What is the “fried egg plot”?

A graph of biomass (B/BMSY) vs fishing pressure (F/FMSY) showing stock status.

What do the 4 quadrants of the fried egg plot represent?

• Healthy: high B, low F

• Overfishing: high F

• Overfished: low B

• Rebuilding/depleted: low B, low F

What does “fully fished” mean?

Stock is being harvested at maximum sustainable level (≈ MSY).

Why is “fully fished” NOT the same as overfished?

It is sustainable (at MSY), not depleted below safe levels.

Current status of global fish stocks?

~90% are fully exploited or overfished; ~34% are overfished.

Major commercial fishing methods?

Trawling, longlining, purse seining, driftnetting, trolling.

What is gear selectivity?

How specific a fishing method is in targeting certain species/sizes.

What is bycatch?

Unintended capture of non-target species.

Why is bycatch a problem?

Causes mortality of non-target species and ecosystem impacts.

What are MPAs (Marine Protected Areas)?

Areas where fishing is restricted or banned to protect ecosystems.

Main benefit of MPAs?

Increased biodiversity and stock recovery.

What is Monterey Bay Aquarium Seafood Watch?

A program that guides consumers toward sustainable seafood choices.

How does Seafood Watch help fisheries?

Encourages sustainable practices through consumer demand.

What are types of aquaculture?

Net pens, ponds (e.g., shrimp), recirculating systems.

Pros of aquaculture?

• Reliable food supply

• Reduces pressure on wild fish

Cons of aquaculture?

• Disease

• Pollution

• Escapes

• Feed sourcing issues

How does shoreline modification affect fish?

Reduces habitat complexity (less cover/spawning habitat) → lowers productivity.

Sources of excess nutrients in lakes?

Runoff (especially livestock/agriculture), fertilizers, and watershed inputs.

Impacts of excess nutrients?

Eutrophication → algal blooms, low oxygen, fish stress/death.

Why are contaminants a common issue in lakes?

Lakes collect pollutants from the entire watershed and retain them for long periods.

What is biomagnification?

Increase in contaminant concentration up the food chain.

Why are contaminants highest in large, old fish?

They accumulate toxins over time and eat many contaminated prey.

How can mercury be present in pristine Montana lakes?

Natural geology (cinnabar) and atmospheric deposition.

Ways to manage contaminated fisheries?

• Fish consumption advisories

• Limit pollution inputs

• Cleanup efforts

• Time (natural decline)

Zebra & quagga mussels origin?

Native to Eastern Europe.

How did they get to the U.S.?

Ballast water from ships.

Why are they a concern for Montana?

They spread rapidly, damage ecosystems/infrastructure, and are hard to control.

How is Montana preventing mussel spread?

Boat inspections, education, and monitoring (eDNA).

What is a run-of-river reservoir?

Minimal storage; water flows through with little fluctuation.

What is a storage reservoir?

Stores water for later use (large seasonal fluctuations).

Upstream fish passage considerations?

Fish ladders, dam removal, transport systems, maintaining migration routes.

Downstream fish passage issues?

Injury from turbines, pressure changes, predation, disorientation.

Downstream passage solutions?

Bypass systems, improved turbine design, fish transport

Typical water level pattern in western reservoirs?

Winter drawdown → spring refill → summer irrigation release.

How do water level fluctuations affect fish?

Reduce shoreline habitat, spawning areas, and overall productivity.

Major sources of sediment in streams?

Land disturbance, roads, and eroding/unstable stream banks.

Why are trout/salmon redds sensitive to sediment?

Fine sediment clogs gravel, reducing oxygen flow and preventing egg survival/emergence.

How is fine sediment measured in streams?

Substrate coring in redds (percent fine sediment).

Solutions to reduce sediment?

• Bank stabilization

• Riparian vegetation restoration

• Road removal/improvement

• Habitat protection

How do irrigation canals affect fisheries?

• Block migration

• Trap fish in canals

• Cause stream dewatering

Solutions to irrigation canal impacts?

• Fish screens & bypass systems

• Fish ladders

• Fish salvage

• Managed drawdown

When does summer dewatering occur?

During heavy irrigation withdrawals (low natural flows).

Why is dewatering a problem?

Reduces habitat, blocks migration, and can kill fish.

Solutions to dewatering?

• Instream flow protection

• Water leasing

Why are tailwaters highly productive?

Stable flows, high nutrients, and optimal temperatures.

Role of dam outlet depth?

Controls water temperature (deep = cold, surface = warm).

Cause of fishkills below Ennis Dam (Madison River)?

Warm water from shallow surface releases.

Solution to Ennis Dam fishkills?

Pulsed cold-water releases from Hebgen Reservoir.

Other potential solutions considered?

Changing outlet structure or modifying dam operations (flow/temp control).

Common tailwater problems?

• Temperature issues

• Inadequate flows

• Lack of sediment/gravel

Common tailwater solutions?

• Adjust outlet depth

• Controlled flow releases

• Flushing flows to move sediment