Threats to Vertebrates

Question 1

Main areas looked at

Answer 1

Overexploitation - fishing industry, hunting, pet trade
Habitat destruction - land, aquaculture, pollution
Invasive species

Question 2

Key points fishing overexploitation

Answer 2

• Seafood from wild stocks is insufficient to meet growing demand
• > 70% of the worlds fish stocks are either fully exploited or depleted
• Stocks of many of worlds great fisheries now at <10% of unexploited levels
• As shallow water stocks are depleted, the global fishing fleet is seeking fish from deeper water
• Almost nowhere less than 1,500m deep that is not exploited
• Technology improvements - Diesel engines, sonar location, GPS, larger more efficient nets, driftnets
• Industry is now twice as large as necessary

Question 3

Studies into overexplotation of fish

Answer 3

Naylor et al., 2000
North sea exploitation of fish for fish food has saw a decrease in cod, seal and seabird populations

Pauly 1987
Exploitation of anchoveta in Peruvian upwelling system has saw to a decline in seabird and mammal populations

Question 4

Study into hunting

Answer 4

Challender and MacMillan, 2014

• Poaching major problem with regards to animal threats
• Tiger (Panthera tigris) populations continue to decline despite massive input of money into poaching prevention and goals to double tiger population by 2022
• Chinese pangolin (Manis pentadactyla) population fallen by >94%
• Asiatic black bears (Ursus thibetanus) declines in population of ~49%

Question 5

Study into the pet trade

Answer 5

Harris et al., 2015

• Pet trade involves 1/3 of the worlds bird species
• study looked at 38 Indonesian bird species, 14 were declining
• All 14 of these declining species were traded regularly, none of the untraded birds were declining
• trade not habitat loss contributing

Question 6

Study into habitat loss IUCN re-evaluation

Answer 6

Ocampo-Penuela et al., 2016

• Looked into 586 endemic bird species from 6 of the worlds most biodiverse and threatened places
• Found that of these birds, 18% were on the IUCN red list as threatened by habitat loss
• Re-evaluating these species found that the number threatened by habitat loss was much higher ~43%

Question 7

Study into habitat loss bats

Answer 7

Muylaert et al., 2016

• habitat loss will affect bat species richness more than it will small mammals or birds
• bats required at least 47% of their available habitat to maintain species richness while small mammals needed only 30% and understory birds were between 30-50%

Question 8

Studies into mangrove destruction

Answer 8

Primavera (1997 + 1998)
Hundreds of thousands of hectares of magroves and coastal wetlands transformed to milkfish and shrimp ponds
- loss of ecosystem services provided by mangroves; nurseries for juvenile finfish, coastal protection, flood control and sediment trapping

Ogden 1988
mangrove destruction can impact negatively on sea grass beds and coral reefs

Question 9

Studies into TBT pollution

Answer 9

Schulte-Oehlmann et al., 1996
Hydrobia ulvae increased levels of imposex and reproductive failure

Feraro et al., 2004
Showed that TBT had mutagenic effects on fish nucleus
Study on traira (Hopius malabaricus)

Zhang et al., 2016
Can induce obesogen response in goldfish (Carassius auratus)
- increased food and weight gain

Question 10

Study into pollution solids

Answer 10

Wilcox et al., 2016

• Ingestion and entanglement from litter poses bigger threat to marine fauna than chemical pollutions
• Fishing gear, balloons and plastic bags are the biggest entanglement threats to marine fauna
• plastic bags and utensils are the biggest ingestion risk to seabirds, turtles and marine animals

Question 11

Info on Nile Perch

Answer 11

Global Invasive Species Database (GISD)
Nile Perch (Lates niloticus)
- Introduced to Lake Victora, Africa in 1954 to counteract the drastic drop in native fish stocks by overfishing
- Contributed to the extinction of >200 endemic fish by predation and competition
- Also oiler than local fish which contributed to more trees being felled to fuel fired to dry them
- This resulted in increased erosion and run off eventually leading to eutrophication and dead zones

Question 12

Info on Brown tree snake

Answer 12

GISD
Brown tree snake (Boiga irregularis)
- Native to Australia, Indonesia, Papua New Guinea and the Solomon Islands
- Thought to have hitchhiked to Guam on military aircraft in the 1940s-1950s
- lack of predators and abundance of prey caused population to explode
- island wide by 1970s
- Resulted in the almost 100% extinction of Guam’s native forest birds