BIO3021 Lecture Notes - Lecture 8: Peruvian Anchoveta, Recreational Fishing, Allometry
25 May 2018
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Lecture 8 – Anthropogenic Selection Pressures: Fisheries and Aquaculture
Brief History of Fishing
• Ability to catch fish increased over time
o Been around for long time
• Exploded from 1950
o Low in 1946 because of war
Many Fisheries have collapsed
• Most famous and one of largest Peruvian Anchoveta
• ~350 fisheries have collapsed
• No change in fisheries collapse
o As a result: last 10% fish on planet
• Global Declines
o 1 in 5 people on earth get most of protein from sea
o Peak seafood in 80s
o Next war: over food or fishing grounds?
• Fishing locations are going further south and deeper
Taking Too Many Fish
• Taking far more fish than is sustainable in almost every instance
• Not just commercial fishers: Australia, 50% of fish taken by recreational
fishers
o No treaty or coastal management
Fisheries don’t Recover
• When fish declines occur, recovery is slow to non-existent
• If shut down exploitation – still doesn’t recover
• Cultivation Effects
o Myth: Big fish eat medium sized fish
▪ If take big fish away, no one eats medium sized fish → prey
upon tiny recruits in fishery
• Size Evolution
o People target larger fish
o Reproducing is expensive
Why is Fish Size Important?
• Allometric reproduction
o Reproductive outlet isn’t directed with weight
o Larger impact on babies per year
o E.g. red snapper. One 12.5 kg female = 212 1.1 kg females =
9,300,000 eggs
• Bigger fish make better larvae
o Older, larger females may produce offspring with higher survivorship
probabilities
• Problem: is large female is taken from population – large affect on recruiting
population for next year
o Taking all reproductive potential from population
o Fish have dramatically decreased in size due to overexploitation over
time
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Document Summary
Lecture 8 anthropogenic selection pressures: fisheries and aquaculture. Brief history of fishing: ability to catch fish increased over time, been around for long time, exploded from 1950, low in 1946 because of war. Taking too many fish: taking far more fish than is sustainable in almost every instance, not just commercial fishers: australia, 50% of fish taken by recreational fishers, no treaty or coastal management. Fisheries don"t recover: when fish declines occur, recovery is slow to non-existent, cultivation effects. If shut down exploitation still doesn"t recover: myth: big fish eat medium sized fish. If take big fish away, no one eats medium sized fish prey upon tiny recruits in fishery: size evolution, people target larger fish, reproducing is expensive. Why is fish size important: allometric reproduction, reproductive outlet isn"t directed with weight, larger impact on babies per year, e. g. red snapper. One 12. 5 kg female = 212 1. 1 kg females =
