5 Human Impacts on the Environment: Crash Course Ecology #10

Collapse of the East Coast FisheryCollapse of the East Coast Fishery

Many theories have been suggested Many theories have been suggested to explain the serious decline of the to explain the serious decline of the groundfishgroundfish

To understand, keep in mind that fish To understand, keep in mind that fish are a renewable resource, and all are a renewable resource, and all renewable resources must be renewable resources must be managed properlymanaged properly

Keeping the #’sKeeping the #’s Fish can be harvested forever if the Fish can be harvested forever if the

number of fish caught each year number of fish caught each year does not exceed the number does not exceed the number reaching maturity in that year.reaching maturity in that year.

This is called This is called sustained yield sustained yield managementmanagement

The 5 ReasonsThe 5 Reasons

1.1. OverfishingOverfishing2.2. Improved Fishing TechnologyImproved Fishing Technology3.3. Uncontrolled Foreign FishingUncontrolled Foreign Fishing4.4. Destructive Fishing PracticesDestructive Fishing Practices5.5. Changes in Natural ConditionsChanges in Natural Conditions

1. Overfishing1. Overfishing The catch allowed by the The catch allowed by the

government appears to have been government appears to have been too hightoo high

Scientists may have overestimated Scientists may have overestimated the number of fish becoming adults the number of fish becoming adults each yeareach year

If this did happen (and it did), If this did happen (and it did), sustained yield management was not sustained yield management was not workingworking

2. Improving Fishing Technology2. Improving Fishing Technology

After WWII, larger, more powerful, engine-After WWII, larger, more powerful, engine-driven trawlers were developeddriven trawlers were developed

Technological developments such as sonar Technological developments such as sonar and satellite navigation systems helped and satellite navigation systems helped fishermen locate fish easierfishermen locate fish easier

Over the years, fewer fish escaped the Over the years, fewer fish escaped the nets.nets.

Ironically, the “advances” in technology Ironically, the “advances” in technology made overfishing possible.made overfishing possible.

3. Uncontrolled Foreign Fishing3. Uncontrolled Foreign Fishing By late 1960’s foreign fleets caught more By late 1960’s foreign fleets caught more

fish than sustained yield methods would fish than sustained yield methods would have allowedhave allowed

Countries with ocean coastlines were Countries with ocean coastlines were urging the UN to allow them to extend urging the UN to allow them to extend national fishing limitsnational fishing limits

1977, the UN allowed Canada to extend its 1977, the UN allowed Canada to extend its control seas to 370kmcontrol seas to 370km

Foreign fishing fleets working inside this Foreign fishing fleets working inside this limit had to follow the Cdn limitslimit had to follow the Cdn limits

4. Destructive Fishing Practices4. Destructive Fishing Practices When trawlers were trying to catch one When trawlers were trying to catch one

type of fishtype of fish, for example, cod, many other , for example, cod, many other types of fish may have become caught in types of fish may have become caught in the nets.the nets.

These unwanted fish, which were already These unwanted fish, which were already dead, were usually just thrown away.dead, were usually just thrown away.

Only the remaining fish were reported to Only the remaining fish were reported to authorities as having been caughtauthorities as having been caught

5. Changes in Natural Environment5. Changes in Natural Environment

2 specific changes have been 2 specific changes have been identified:identified:

1.1. Water temperatures and ocean salinity levels Water temperatures and ocean salinity levels have changed since the mid-1980’shave changed since the mid-1980’s. The fish . The fish may have changed their migratory routes to may have changed their migratory routes to avoid areas where these changes have avoid areas where these changes have occurred.occurred.

2.2. Decline of the sealing industry in the late Decline of the sealing industry in the late 1970’s1970’s cause an decrease in groundfish cause an decrease in groundfish population. More seals=more competition for population. More seals=more competition for the same food. Fish lost.the same food. Fish lost.

What Happened to the Grand Banks Cod?