Presented by:

Geonyzl L. Alviola

Bio 243 (Marine Biology)

Human Impacts on Marine

Biota: Fisheries

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Environmental stressors and its effect.

(National Academic Press, 2012)

Humans have interacted with oceans for thousands of years

Moving people and products over vast distancesAccelerated global reach of cultures

Has substantial impact on the environmentMoves resources around the worldFor example:

Ballast water transplants organisms, which maybecome invasive

Studies on Human Impacts on Marine Ecosystem:

Rick, T. C., & Erlandson, J. M. (2008). Human impacts on ancient marine ecosystems: a global perspective. Univ of California Press.

In history:-Several fishing industries have collapsed due to:

- pollution - habitat loss- global warming - introduction of exotic species

- That fishing had evolved in three historical and geographic stages:

a. Aboriginal fisheries, exploration of near shoreb. Colonial exploitation of coastal and continental

shelf ecosystemsc. Global stage marked by “intense and geographically

pervasive exploration of coastal, shelf and oceanic

Emptying the Ocean

13-6

Emptying the oceans• We are placing unprecedented pressure on

marine resources

–Half the world’s marine fish populations

are fully exploited

– 25% of fish population are overexploited and heading to extinction

• 2006 study in Science:

– Predicted that populations of all ocean

species we fish for today will collapse

by the year 204813-7

We have long overfished

• Some species hunted to extinction:

- marine mammals

- whales

- dolphins

- seals

- marine reptiles (sea turtles)

- predatory fishes like sharks

13-8

Fishing has become industrialized

• Driftnets for schools of

herring, sardines, mackerel, sharks

• Longline fishing for tuna and swordfish

• Bottom-trawling for

pelagic fish and groundfish

13-9

Some fishing practices kill non-target animals and damage ecosystems

• By-catch = the accidental capture of

animals

• Drift-netting drowns dolphins, turtles, and seals

– Banned or restricted by many nations

• Longline fishing kills turtles, sharks, and

albatrosses

– 300,000 seabirds die each year

• Bottom-trawling destroys communities

– Likened to clear-cutting and strip mining 13-10

Some fishing practices kill non-target animals and damage

ecosystems (cont’d)

• Catch rates drop precipitously with

industrialized fishing

– 90% of large-bodied fish and sharks are

eliminated within 10 years

– Populations stabilize at 10% of their former

levels

• Marine communities may have been very

different before industrial fishing

– Removing animals at higher trophic levels

allows prey to proliferate and change communities13-11

13-12

Oceans today contain only one-tenth of the large-bodied animals

Several factors mask declines

• Industrialized fishing has depleted stocks, global catch has remained stable for the past 20 years

– Fishing fleets travel longer distances to

reach less-fished portions of the ocean

– Fleets spend more time fishing

– Fishing in deeper water

– Improved technologies: faster ships, sonar

mapping, satellite navigation, thermal sensing, aerial spotting

– Data supplied to international monitoring

agencies may be false 13-13

We are “fishing down the food chain”

• Figures on total global catch do not relate

the species, age, and size of fish harvested

• As fishing increases, the size and age of fish caught decline

– 10-year-old cod, once common, are now rare

• As species become too rare to fish, fleets

target other species

– Shifting from large, desirable species to smaller, less desirable ones

– Entails catching species at lower trophic levels13-14

• The direct effects of fishing can also

influence species diversity at two levels:

• First, by removing components of populations

that may show some genetic differentiation

• Second, by depleting species that are most

vulnerable.

• Large slow growing and late-maturing species

suffer greater population declines

Goulletquer P., Gros P. and Weber J. 2014. The Impacts of Human Activities on Marine Biodiversity. Biodiversity in the Marine Environment, XXI, p.198 DOI 10.1007/978-94-017-8566-2_2,

Aquaculture has benefits and drawbacks

• Aquaculture = farm fisheries

– 30% of the world’s fish production

– Canada is fourth-largest producer of farmed

salmon in the world

– Freshwater fish and shellfish (clams, oysters,

mussels)

– Canada is now authorizing the production of GM salmon

13-16

Aquaculture has benefits and drawbacks (cont’d)

• Benefits

– Improves food security

– Reduces pressure on wild stocks

– 10 to 1000 times more energy-efficient

• Drawbacks

– Increased disease causes antibiotic use

– High-density fishery causes more waste

– Can damage landscape

13-17

Consumer choice can influence marine harvest practices

• Buy eco-labeled seafood– Dolphin-safe or, better yet, pole and line,

tuna

• Use consumer guides– Sea Choice or Seafood Watch seafood

guides

– Some best choices: farmed catfish and

caviar, sardines, Canadian snow crab, Pacific halibut, trap-caught shrimp

– Some to avoid: Atlantic cod and halibut,

wild caviar, imported King crab, shark, farmed shrimp 13-18

Marine biodiversity loss erodes ecosystem services

• 2006 study in Science, showed effects of biodiversity loss on ecosystem

– Less primary and secondary production

– Less able to withstand disturbance

– Reduced habitats for fish and shellfish

– Reduced filtering and detoxification

13-19

Marine Conservation

13-20

Fisheries management has been based on maximum sustainable yield

• Maximum sustainable yield = Maximal

harvest while keeping fish available for the future

• Despite management, stocks have plummeted

• Ecosystem-based management

– Shift away from species and toward the larger

ecosystem

– Consider the impacts of fishing on habitat and species interactions

– Set aside areas of oceans free from human interference

13-21

We can protect areas in the ocean• Marine protected areas (MPAs) = established al

ong the coastlines of developed

countries

– Still allow fishing or other extractive activities

• Marine reserves = areas where fishing is

prohibited

– Leave ecosystems intact, without human

interference

– Improve fisheries, because young fish will

disperse into surrounding areas

• Many commercial, recreation fishers, and

businesses do not support reserves 13-22

Reserves can work for both fish and fishers

• Found that reserves do work as win-win solutions

• In 2001 census by marine scientists stated, that in addition to boosting fish biomass, total catch,

and record-sized fish, marine reserves:

– Within reserve boundaries

• Produce rapid and long-term abundance,

diversity, and productivity

• Decrease mortality and habitat destruction

• Lessen the likelihood of extirpation (local extinction)

13-23

Reserves can work for both fish and fishers (cont’d)

• Marine reserves:

– Outside reserve boundaries

• “Spillover effect” = protected species spread

outside reserve

• Larvae of protected species “seed the sea” outside the reserve

– Improved fishing and ecotourism

13-24

How should reserves be designed?

• 20-50% of the ocean should be protected in no-take reserves – How large? – How many?– Where?

• Involving fishers is crucial fisheries in coming with these answers

13-25

Conclusion

• Oceans cover most of our planet and contains diverse topography and ecosystems

• We are learning about the oceans and

coastal environments, intensifying our use of their resources and causing more severe

impacts

13-26

• Setting aside protected areas of the oceancan serve to maintain natural systems andenhance fisheries

• Look beyond simply making fisheries stableand instead consider restoring the ecologicalsystems that once flourished in our waters

References:

Rick, T. C., & Erlandson, J. M. (2008). Human impacts on ancient marine ecosystems: a global perspective. Univ of California Press.

Goulletquer P., Gros P. and Weber J. 2014. The Impacts of Human Activities on Marine Biodiversity. Biodiversity in the Marine Environment, XXI, p.198 DOI 10.1007/978-94-017-8566-2_2,

Jackson, J. B., Kirby, M. X., Berger, W. H., Bjorndal, K. A., Botsford, L. W., Bourque, B. J., & Hughes, T. P. (2001). Historical overfishing and the recent collapse of coastal ecosystems. science, 293(5530), 629-637.

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