Conservation

Question 1

Anthropocene extinction

Answer 1

Losing species, much of this directly related to overgrown over consumptive human population

Question 2

Most extinctions occur in ____

Answer 2

isolated freshwater water systems (95.9%) as marine fishes are less vulnerable due to large populations connected populations (but many are now commercially extinct e.g., Northern cod)

• Worldwide, considering areas with uncatalogued species, estimates suggest 20 - 35% (~3000+) freshwater vs. 5% (~1000) marine fishes have gone extinct since 1900

Question 3

Major causes of fish extinction

Answer 3

habitat change and species introductions

Question 4

Recent fish extinctions

Answer 4

Since 2011, 52 more fish extinctions worldwide and 12 just in North America

Question 5

Freshwater extinction susceptibility (6)

Answer 5

• Increasing probability of extinction where freshwater fishes are typically in closer contact with human activities than are marine ones
• Many freshwater fish are endemics, adapted to unique habitats occurring nowhere else in the world
• Isolated streams, rivers, and lakes can be destroyed by
• Pollution
• Introduced species for aquaculture
• habitat alterations

Question 6

General causes of fish biodiversity loss (8)

Answer 6

• Bottom type modification
• Channelization
• Damming
• Watershed perturbations
• Introduced species
• Pollution
• Exploitation
• Climate change

Question 7

Bottom type modification

Answer 7

• Activities disrupting or removing bottom structure disrupts essential fish species habitat

Dredging carves deep trenches to keep shipping channels open

Trawling, mining and anchoring

Reduce essential habitat for key fish species and can cause important shifts in species interactions
* Removing structure

Question 8

Channelisation or bank stabilisation

Answer 8

Straightens river with smooth sides Reduces floodplain flooding Increased land use in floodplain Decouples land from water resources

Reduces cleaning potential of floodplain
Increases flow and erosion
Water levels must be maintained
Increases leeching and waste runoff in channel and eventually elsewhere
Decreases fish diversity, and changes assemblages favouring high disturbance species

Question 9

Dams

Answer 9

Provide hydroelectric power water storage and increased water for agricultural and domestic use
* Cause generally poor water management, high erosion and silt accumulation which must be removed
* Tropical countries, increased standing water conduit for pathogens
* Alters hydrology and changes fish assemblages just as bottom type modification in rivers can

Question 10

Fish ladders

Answer 10

used to help with damning, good but fish need to find the ladders

Question 11

Watershed perturbations

Answer 11

Changes in landscape use within watersheds has impact on aquatic species (logging, agriculture expansion, mining)

can change water chemistry, flow and temperature regimes, habitat types within aquatic systems

Question 12

Introduced species

Answer 12

(nonindigenous, invasive, alien)
can be accidental or intentional

Question 13

Homogenisation

Answer 13

Introduced species are often an added stressor to an already stressed systems
* With greater disturbance specialised endemics lose essential habitat and are displaced by native generalists
* At local scale, system shows overall diversity increase, but as endemics disappear, diversity drops
* Addition of alien species may also initially increase diversity, but the long-term impacts are unpredictable

Question 14

introduced species are common additions, they can make very different systems become increasingly_____

Answer 14

homogenous

Question 15

Predator release hypothesis

Answer 15

In their native range, the species have natural predators, competitors, parasites and environmental tolerances that keep them in check

• In their introduced environments predators, and other controls are substantially reduced allowing species to increase almost uncontrollably

Question 16

How do Species introductions lead to the reductions of native species populations

Answer 16

• Directly through predation on adults, young, or eggs
  Nile Perch
• Indirectly by being a superior competitor, by hybridization, or the transmission of other non- native parasites and pathogens into local populations

Question 17

Predation example, Nile perch

Answer 17

In lake Victoria;
Nile Perch introduced in 1960s convert useless (small bony) cichlids to large fish biomass

Nile perch wiped out most haplochomines and other endemic species, turning to cannibalism as main food source

• Algae eaters went extinct and increasing agriculture in area caused increasingly turbid waters and low CO2
• Converted a complex food-web and intricately niche packed system into a simplified community, with reduced fish biodiversity in less than 30 years

Question 18

Competition example, Arctic cod

Answer 18

Arctic cod is a Keystone planktivore in most Arctic marine food webs
* Increasing evidence show that Capelin, a north Atlantic species are moving north and show high niche overlap with Arctic cod in Southern Beaufort Sea
* Fear is that warming Arctic causing will cause competitive exclusion of Arctic cod as Capelin invading

Question 19

Pollution – Contaminants

Answer 19

Human produced substances (1000s) with toxic elements
Direct toxicity to fish by interfering with developmental pathways

Have indirect impacts through food chains (eutrophication or bioaccumulation) inhibiting survival and reproduction

Enter aquatic systems attached to sediments, dissolved in water or in the air

Question 20

Agricultural pollution

Answer 20

Pesticides, herbicides and fertilizers – responsible for extermination of many fishes in isolated habitats world-wide

• Increases in fertilizer/nutrients loads also increase algal blooms which decrease CO2 when blooms die and decompose

Question 21

Endocrine disruptors

Answer 21

Chemicals interfering with growth and development at low concentrations
* Can act early during sex determination but also later in the development of gonads and germline cells

• Documented impacts include:
• Abnormal gonad morphology
• Reduced rate of sperm/egg production - Reduced quality of gametes
• Failure to mature
• Chemical pollutants often act in concert or with other factors to exacerbate fish population declines

Question 22

Commercial exploitation

Answer 22

Most of the world’s commercial fisheries either collapsed or overexploited

Fish continue to be major source of protein and
essential fatty acids (FA) to human population

• So, fishing will continue but with fewer sustainable resources available

Question 23

Natural vs Human predation

Answer 23

Natural predation
- Focused on young, most abundant cohorts
- sick/dying individuals
- Easy meal
Weeding out less fit individuals sustainable

Human predation
- Indiscriminate
– targeting entire local aggregates (populations)
- Healthy/larger individuals
- Often targeting those of prime
reproductive age (e.g., salmon)
Decimation of populations not sustainable

Question 24

Overfishing – example

Answer 24

• Overfishing is the removal of species at rate it cannot replenish, resulting in species becoming depleted or underpopulated in given area over time
• Purse seine fishery for Pacific Sardine began in late 1800s, and became the largest marine fishery off California by 1925
• 175,000 t canned and waste reduced for feed
  Reduced fish value became greater than actual fish, leading to floating reduction plants operating outside legal zones of catch restrictions
• Catches increased to 790,000 t in 1937, with a mean of 600,000 t/year for 10 years
• Estimated yields, however, were at 250,000 t/year max
• Pattern repeated in many exploited species; Atlantic herring, Northern Cod, Anchoveta in Peru, Mexican Totoaba etc,…

Question 25

Overfishing – Socio-economic and socio- ecological views on overfishing

Answer 25

Many nuanced sociopolitical and socioeconomic implications also drive species commercial extinction – related back to human overpopulation and overconsumption

Question 26

Climate change

Answer 26

Although world is working to change this, Atmospheric emissions of Greenhouse gases are at highest levels ever * Already seeing impact on ocean levels and ocean current shifts * Precipitate massive weather changes with increasing climate extremes, floods, droughts, and storms * Changing physical chemical and biological integrity of marine and Freshwater systems

Question 27

Climate change – Consequences

Answer 27

Impact species abundances, phenology, trophic relationships, migration patterns, distributions, and genetic integrity and diversity and will generate no-analog communities and ecosystems * Arctic marine ecosystems especially vulnerable where warming is occurring at 2-3 x global average * Coral reef ecosystems, hotspots for fish biodiversity, also vulnerable to even moderate temperature changes

Question 28

What can be done

Answer 28

1. Pass national / international legislation promoting sustainable resource use, and enforce this legislation 2. Make marine and freshwater reserves, as large as feasible 3. Promote ecosystem-based management and evolutionarily compatible predation 4. Be precautionary: act despite uncertainty, without waiting for scientific consensus 5. Monitor results and manage adaptively 6. Promote eco-certification efforts and other programs rewarding sustainable fishing 7. Avoid techno-arrogance, e.g., technological fixes treating symptoms rather than causes 8. Restore degraded habitat promoting recovery of imperiled species, and engage in captive breeding of endangered species as a last resort 9. Educate resource users and public about biodiversity loss and sustainable use 10. Include all users at all stages in management decisions, and encourage local/community control wherever possible 11. Reduce fishing effort and eliminate subsidies that encourage overfishing