intro to fisheries management Flashcards
4 steps to fisheries management
1.collect data
2.asses stays of stocks
3.set catch targets
4.make regulations
what is overfishing essentially
exceeding the reproductive capacity of fish - causes a decline, and possibly collapse, in the stock.
3 types of overfishing
growth overfishing
recruitment overfishing
ecosystem overfishing
what is growth overfishing
- Harvesting fish before they have a chance to reach their full growth potential - fish are harvested at an average size that is smaller than the size that would produce the maximum yield per recruit.
- Reduces average mass of individuals in the catch
what is recruitment overfishing
- Reducing a stock so much the spawning stock is too low for the stock to maintain itself.
- Leads to population decline
what is ecosystem overfishing
Altering the balance of the ecosystem by overfishing
wats Maximum sustainable yield
The largest yield that can be harvested from a stock indefinitely
3 ways to control catches
limiting catch
limiting fishing efforts
limiting access
how can we limit catch as a way to control catches
- Minimum landing sizes - creates a large number of discards (minimum mesh sizes remove this problem, but choice of mesh is complicated - fish of different species are different sizes)
- Directing technology (e.g. Minimum Mesh
Sizes) - Catch quotas
how can we limit fishing efforts as a way to control catches
- Prohibiting technology (e.g. types of nets)
- Limit on number (fish traps) or size (nets)
- Restricting number of vessels
- Limiting average time at sea - essentially creates “seasons” - bigger populations allow longer seasons
how can we limit access as a way to control catches
Marine reserves - Marine Protected Areas (MPAs, No-Take Zones..)
The problem with minimum mesh sizes as a way to limit catch
- Eggs are produced in proportion to a fish’s volume, which is proportional to the cube of its length
- More importantly, older, larger female fish produce eggs and larvae that are much more likely to survive
- Larvae of 12-year-old rockfish grew four times faster
than larvae produced by 5-year old fish - longer in plankton = more time to be eaten
what is a Total Allowable Catch (TACs)
catch limits (quotas), expressed in tonnes or numbers, set for most commercial EU fish stocks
- In the EU, each country is given a quota based upon the calculated TAC and their traditional share (as a
percentage)
- this creates a high amount of discards - so the EU has applied a Discard Ban
- Fish with known high survival rates are to be released alive - all other fish caught would be landed and counted against the quotas
- Undersized fish can only be sold for fish meal or pet
food production
- Fish caught in excess of individual quotas can be
marketed normally but quotas must be bought or leased from another vessel owner in the same member state
the main purpose of the discard ban
to increase selectivity in fisheries, especially through the use of technology
what is Regional Fisheries Management Organisations (RFMOs)
dedicated to the sustainable management of
either species or areas - some have a purely advisory role, most have management powers to set catch and fishing effort limits, technical measures, and control obligations
what’s B/BMSY when working out current fishery status
biomass scaled by biomass at maximum sustainable yield
- < 1 = overfished stock
what’s F/FMSY when working out current fishery status
fishing pressure scaled by the fishing pressure
that would generate maximum sustainable
yield
- > 1 = overfishing
what’s the Relationship between B/BMSY and F/FMSY
- EXAMPLE 1: a small-scale fishery with biomass B/BMSY = 0.3 (overfished) and fishing pressure F/FMSY = 1.7 (overfishing) would actually be near bionomic equilibrium. Biomass and profit would be
low, but stable from year to year. Because the stock has been overfished, the catch is also small—in this case, it is just one half of MSY - EXAMPLE 2: a fishery with B/BMSY = 0.4 and F/FMSY = 2.5; biomass is lower than optimal and still declining. Despite the low biomass, fishing mortality is so large that harvest remains high (in this case =
MSY). Ultimately, this pressure will reduce the stock, but the inevitable economic and food provision consequences of that overexploitation have yet to be realized.
what are the 4 objectives to sustain healthy marine ecosystems and the fisheries they support
(i)avoid degradation of ecosystems, as measured by indicators of environmental quality and system status
(ii) minimize the risk of irreversible change to natural assemblages of species and ecosystem processes
(iii) obtain and maintain long-term socioeconomic benefits without compromising the ecosystem
(iv) generate knowledge of ecosystem processes sufficient to understand the likely consequences of human actions
why does Ecosystem-based management differ from management based around single (or even mixed)
species
A fishery could be considered overfished within the ecosystem plan (ecosystem overfishing) when it is not overfished in a single-species context
E.g. When overfishing of large predators causes food web shifts
what 2 hypothesised processes are Fish biomass exported from MPAs based on
- Enhanced spawning stock biomass (very difficult to conclusively demonstrate)
- Export of adult fish to areas open to fishing through spillover - either density-independent or density-dependent movements
what 5 key features do global conservation outcomes depend on marine protected areas with
NEOLI (No-take, Enforced, Old, Large, Isolated) - Edgar et al. (2015)
1. Degree of fishing permitted within MPAs
2. Level of enforcement
3. MPA age
4. MPA size
5. Presence of continuous habitat allowing unconstrained movement of fish across MPA boundaries
- recovery of fish biomass results dramatically improve when MPA possesses 4 or more NEOLI features
what could happen in 2050 according to Costello et al (2016) if sound management reforms were applied to
global fisheries e.g. Rights-based Fishery Management (RBFM) + fishing effort for maximum sustainable yield (FMSY)
could generate annual increases exceeding 16 million metric tons (MMT) in catch, $53 billion in profit, and 619 MMT in biomass relative to business as usual.
despite different mechanisms to try and control catch numbers, where will the bulk of the increase in fish consumption come from
aquaculture
