Glossary for fisheries sustainability survey


Biomass, or the index of biomass, is the total weight of a given species of fish in one area at a specific time. This can be for a full population or a defined portion of it. The time periods are usually the time of the survey or measurement.

Biomass maximum sustainable yield is the biomass level for a species where harvest of this species is maximized. This is influenced by the health of the fish population and other environmental factors.


Bycatch is the unintentional catch of a species when meaning to catch another. In many fisheries, it’s not possible to directly fish for one species without also capturing others, including:

Cautious zone

A stock is considered to be in the cautious zone if the biomass, or the index of biomass, is higher than the limit reference point but lower than the upper stock reference point.

This means it’s greater than 40% of biomass maximum sustainable yield but lower than 80% of the yield.

Critical zone

A stock is considered to be in the critical zone if the mature biomass, or its index, is less than the limit reference point. This means it’s less than or equal to 40% of biomass maximum sustainable yield, which is where serious harm is likely occurring to the stock.

Conservation harvesting plan

Conservation harvesting plans are fishing plans that identify harvesting methods aimed at minimizing the harvest of small fish and bycatch of groundfish. Plans typically include measures to control and monitor:

Fish stock

Fish stock is a population of individuals of a species found in a particular area. The term is used as a unit for fisheries management, such as the Northwest Atlantic Fisheries Organization area 4R herring.

Fishing gear

Fishing gear is a tool used to capture fish, such as a gill or seine net.

Forage species

A forage species is one that is below the top of an aquatic food chain. It’s an important source of food for at least some other aquatic species, and it experiences high mortality from these predators.

Harvest decision rule

A harvest decision rule is also called a harvest control rule. This is a set of defined management actions for each precautionary approach stock status zone that:

Healthy zone

A stock is considered to be in the healthy zone if its biomass, or the index of the biomass, is higher than its upper stock reference point. This means it would be higher than 80% of biomass maximum sustainable yield.

Limit reference point

The limit reference point is the boundary between the cautious and critical zones. Serious harm is occurring to the stock in the level below this point.

At this stock status level, there may be impacts to the ecosystem and associated species. There may also be long-term loss of fishing opportunities.

Precautionary approach

The precautionary approach is the way fisheries management exercises caution when scientific information is uncertain, unreliable or inadequate. It involves taking action to prevent serious harm even when we don’t have adequate scientific information to prove the need for such action.


Sustainability means a species can survive and meet the needs of their present population without weakening the chances of future generations to meet their own needs. Sustainability reflects the capacity to thrive over the long term.

Uncertain stock status

The uncertain status means we don’t have enough information to assign the stock to a precautionary approach zone. This doesn’t mean there’s no information about a stock, just that we haven’t identified reference points, or that some other data isn’t available.

Upper stock reference point

The upper stock reference point is the boundary between the healthy and cautious zones. When a fish stock level falls below this point, we must reduce the harvesting removal rate to avoid serious harm to the stock.