overfishing

overfishing

• catchcing marine creatures faster than they can reproduce

reef fisheries

key source of household protein, micronutrients and income for many communities

• recent increases → Malthusian basic theory

Malthusian basic theory

This theory posits that population increases geometrically while food production increases arithmetically, leading to inevitable shortages. It suggests that unless checked by factors like famine, disease, or war, population growth will outpace resources, resulting in a struggle for survival and potential societal collapse.

groeth overfishing

• too many fish are caught while v small

• groupers → change sex w age, critical shortage in one sex

recruitment overfishing

• reprod failure → depletion of breeders

demographic o

• turns pop w many age groups into a pop w only one or two sig age classes doing most of the breeding→ pop vulnerable to yrs when neatural fluctuation - poor surival of young

genetic overfishing

serial overfifhing

depletion of one targeted spp after another

ecosystem overfishing

cause great changes in spp composition and functional loss of key spp→ LT community changes

Malthusian overfishing

directly related to human pop

Biggest driver decline of CR

climate change

overfishing impacts

• reduces spp D

• loss of keystone spp

• neg effects on reef processes

• reduced resiliencen and phase shifts

jamaica case study

• pop growth→ 0.5 million 1870 to 2.5 mil by 1994

1960s

fish biomass reduced by 80% due to fish trapping

• large changes in fish predatory spp largely eliminated

• remainging herbivores below reprod size

1980

hurricane allen struck jamaicas reefs → extensive damage

1983

mass mortality of Diadema→ due to a pathogen

• blooms of macroalgae in absence of herbivory

• adult corals killed by algal overgroeth and coral recruitment failing

coral -alagal phase shifts

A significant ecological change where healthy reefs dominated by corals transition to areas dominated by macroalgae. This shift is often driven by factors like nutrient pollution, overfishing, and climate change, leading to reduced coral growth and resilience.

pre columbus

turtles were hugely abundant

• 33-39 million in carribean

dynamite blast fishing

• introduced to Indonesia durin WW2

• used WW2 ammunition shells but now made w chem fertilisers

• fishers hunt for schooling fish and follow blast, divers enter water to collect stunned fish

• reduces coral → rubble

• recruitment of new corals → slow