Lecture 11 - Climate Change and Fisheries

Climate Change and the Ocean - list effects of climate change

Increased temperatures

Reduced O2 availability

Sea level rise

Reduced ice cover

Coral bleaching

Ocean acidification

Effects on fish growth, distribution, and behavior

Effects of Ocean Acidification

pH is a measure of hydrogen ions

Ocean pH used to be 8.25, now 8.05

• Lower pH, more acidic

H2CO3 is carbonic acid

In ocean, reduces itself to carbonic bi acid

Carbonate and calcium already exists in the ocean, which organisms like coral, conch, and crabs use to build calcium carbonate shells / skeletons

More H+ ions = decrease in pH

Decrease in pH = less carbonate (which binds with H+)

Less carbonate = less ability to make calcium carbonate skeleton

Phytoplankton and zooplankton also use calcium carbonate to build their shells

• Reduced calcification because less carbonate ions

The consequences of this would be

• Less oxygen to consume

What impacts would changes in climate create on fisheries?

Spawning, larval survival and recruitment, growth, distribution patterns, range shifts, fish behavior

What is spawning

Very often temperature dependent

Shifts in time of spawning > shifts in distributions, higher mortality, maybe less food availability

• Mismatch hypothesis

what is the mismatch hypothesis

Changes in ocean chemistry can cause shifts in timing of food availability for larvae

Climate change and fisheries: larval survival and distribution

Larval survival and distribution can be temperature dependent

• O2, density, salinity

Different environmental preferences and limits

Most common response is a change is spatial distribution

climate change and fisheries: growth

European Sea Bass

Study raised 12,000 larvae to juveniles in 21 degrees C and 17 degres C

21 degres C fish heavier and faster metabolism

This would impact their survival because they need more food to supplement their metabolism, and move slower to escape predators because they’re heavier

climate change and fisheries: distribution patterns

distribution patterns are affected by many factors:

Food availability, temperature, light level, currents, predators, oxygen, water chemistry

Range Shifts - copepods

Increased temperatures are leading to changes in species range

Copepod assemblage in North America

Warm water species moved north by 10 degrees latitude

Cold water species numbers decreased

range shifts - fish

to anticipate the response of fish populations to climate change, the study developed a framework that integrates requirements in all life stages to assess impacts across the entire life cycle

Each life stage:

• Habitat requirement

• Habitat availability

• Habitat connectivity

Key result – larval dispersion major unknown

Specific habitat requirements

• Spawning (herring)

• Nursery grounds (plaice)

Anchovy could cope best

Plaice least resilient

• Connectivity between spawning and nursery grounds

North sea herring, Norwegian cod, Biscay anchovy

• Contrasting impacts depending on life stage

Climate Change and fisheries: fish behavior

Marine fish larval stage rely on olfactory cues to locate reef and settlement habitat

Excess CO2 (lower pH) impairs olfactory discrimination and homing ability

can organisms adapt?

Echinoderms can regenerate

Can regenerate arms even in acidic conditions

No decrease in CaCO3

Decreased muscle mass (using energy from muscle mass to regenerate arms)

Climate change and fisheries: catch potential

Increased catch in arctic and sub-arctic

Decreased catch in tropics

Economic effects

• Fish price increase because reduced catches

• Demand decrease because of price, reducing potential for price increase

• Livelihoods of fisherman

what can we do??

Fish stocks are more robust to climate change if combined stresses from overfishing, habitat degradation, pollution runoff, land-use transformation, competing aquatic resources, and other anthropogenic factors are minimized.

Reducing greenhouse gas emissions!!!

• Diminish ecological impacts

• Cost of adapting to climate change would be lower, though long term perhaps not sustainable