Quiz
Human interactions and Fisheries
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Questions in this quiz (30)
1Fisheries science
Fisheries management is all about modelling (predicting) the likely [blank_start]size or biomass of target[blank_end] fish species of distinct size/age classes
Critical factor is the [blank_start]recruitment[blank_end].
Recruitment – number of fish reaching a certain [blank_start]age/size[blank_end] or [blank_start]position in the life cycle[blank_end] - when they enter the fishery.- Asize or biomass of target
- Brecruitment
- Cage/size
- Dposition in the life cycle
2Stock assessment
Fundamental basics – level of fishing [blank_start]mortality[blank_end] must be balanced by [blank_start]recruitment[blank_end] and [blank_start]growth[blank_end]
If max mortality level is exceeded, stock will [blank_start]fall[blank_end], and capacity to [blank_start]rebuild[blank_end] will be reduced- Amortality
- Brecruitment
- Cgrowth
- Dfall
- Erebuild
3Important terms:
Recruit: A fish that [blank_start]survives[blank_end] from egg until reproductive (or legal fishery) age
[blank_start]Yield[blank_end]: numbers of fish (or value) produced by the recruits and available to the fishery
Collapse – point where a fished population or stock cannot [blank_start]sustain itself[blank_end]. May be arbitrarily set at [blank_start]10%[blank_end] of pre-fished biomass (or 50% MSY)
[blank_start]Stock[blank_end] – part of a species population that is reproductively isolated and managed as a single unit- Asurvives
- BYield
- C10%
- DStock
- Esustain itself
4Fishery at MSY
In theory, fishing at MSY is desirable for all:
Keeps fishing level and stock size relatively high – approx. [blank_start]50%[blank_end] of maximum stock size
Management aim is to regulate fishing to keep population size at MSY- A50%
5Summary MSY and stock assessment
Typically fishing at MSY keeps the biomass lower (c. 50-75% lower) than the unfished biomass –
Fishing to MSY is risky – if the [blank_start]environment[blank_end] changes it can be easy to [blank_start]overestimate[blank_end] MSY
MSY usually estimated by species – but species interact: [blank_start]ecosystem[blank_end] approach may be better…- Aenvironment
- Boverestimate
- Cecosystem
6Growth in fish supply outpaces [blank_start]population growth[blank_end] (3.2% per year vs 1.6% per year)
Mostly met by aquaculture, mostly in [blank_start]China[blank_end]- Apopulation growth
- BChina
7Global marine capture c. 80 million tonnes:
10% [blank_start]tuna and tuna-like[blank_end] species
Expansion in NW and WC Pacific, Indian Oceans, contraction in Atlantic and Mediterranean
[blank_start]58 Million[blank_end] people engaged in capture fisheries worldwide- Atuna and tuna-like
- B58 Million
8aquaculture
[blank_start]6%[blank_end] growth per year: 94 million tonnes in 2012, of which 66 Million tonnes is food fish, 23 Million tonnes aquatic algae.
China c. [blank_start]50%[blank_end] of global production
20 million people are engaged in aquaculture (>90% in China)- A6%
- B50%
9social
Fish capture and production large source of [blank_start]employment[blank_end] for women (especially in developing countries)
More than 15% primary capture employment women and up to 90% processing employment
Fishing and aquaculture assure livelihoods of c. [blank_start]10%[blank_end] of world’s population- Aemployment
- B10%
10Trends – doom and gloom?
Collapsed species
Fishing down food chain
Fishing deeper
Loss [blank_start]apex predators[blank_end]
PP utilized- Aapex predators
11Types of fishery data:
Research survey - [blank_start]Highest resolution[blank_end] – direct measure of biomass for all species collected in the survey. Limited [blank_start]focus[blank_end], few comparative datasets
[blank_start]Stock assessment[blank_end] - Estimate of biomass for specific populations of species based on survey and catch effort data – only data on few targeted species
Catch data - Reported biomass of [blank_start]landed species[blank_end]. Global in scope, but does not reflect [blank_start]discards[blank_end] and IUU, and is influenced by accidental and deliberate [blank_start]mis-reporting[blank_end], changes in regulation and markets.- AHighest resolution
- Bfocus
- CStock assessment
- Dlanded species
- Ediscards
- Fmis-reporting
12Catch data do not track biomass because other things can influence catch (e.g. changes in [blank_start]restrictions[blank_end], market prices for specific species, [blank_start]fuel[blank_end] prices, vessel exclusions, population [blank_start]shifts[blank_end]).
Also, in a random stationary time series, maximum catch is likely to [blank_start]increase[blank_end] with a longer time series (so more chance of having collapse figures over time)- Arestrictions
- Bfuel
- Cshifts
- Dincrease
13Summary so far
Estimating how many fish have been caught is difficult
Catch and effort data are biased in complex ways as these reflect [blank_start]socio-economics[blank_end] and [blank_start]geopolitics[blank_end] as well as ecology/biology
Satellite and big data approaches are changing the way we understand, measure and police global fishing efforts- Asocio-economics
- Bgeopolitics
14Fishing effects
Direct removal of target species
Changes in [blank_start]size[blank_end] structure of target populations
Alterations to [blank_start]non-target[blank_end] populations of fish and benthos
Alterations to physical environment
Food chain effects (trophic [blank_start]cascades[blank_end], altered [blank_start]predation[blank_end] pressure)- Asize
- Bnon-target
- Ccascades
- Dpredation
15Fishing down (through) the food chain
Pauly et al (1998). Fishing Down Marine Food Webs. Science 279: 860-863.
Most food fish were trophic levels 4.0-4.5
Argument that we are now moving our predation [blank_start]down a trophic level[blank_end] from 4 to 3 (fishing down).
Also by removing predators, [blank_start]low[blank_end] trophic level biomass expands, decreasing mean TL (fishing through)- Adown a trophic level
- Blow
16Alternative : Catch TL is not the same as ecosystem TL
Theoretical comparison based on simulation ecosystem [blank_start]models[blank_end] (week 3)
Catch TL poor reflection of ecosystem TL when catch is [blank_start]selective[blank_end] within the food web- Amodels
- Bselective
17Recent data from research trawls are suggesting that deep-sea fish species (including by-catch) biomass is [blank_start]on the decline[blank_end].
- Aon the decline
18Summary: state of world fish
Globally, best estimate is that c. [blank_start]30%[blank_end] of fish stocks are over fished, [blank_start]60%[blank_end] are fully exploited, and 10% are underexploited
Aquaculture provides [blank_start]more[blank_end] fish than capture fisheries
Long history of management failure, stock collapse.
Current ecosystems have low [blank_start]abundance[blank_end] and [blank_start]diversity[blank_end] with [blank_start]small[blank_end] body sizes. Top predators heavily [blank_start]depleted[blank_end]
Catch data easily available but may give [blank_start]flawed[blank_end] picture of ecosystem state and trends
Rebuilding occurring in heavily regulated fisheries
[blank_start]Satellite[blank_end] vessel monitoring and big data processing give us a much richer view of fishing effort
More to be done in developing world fisheries- A30%
- B60%
- Cmore
- Dabundance
- Ediversity
- Fsmall
- Gdepleted
- Hflawed
- ISatellite
19Fill in the blank
- ACarrying capacity
20Fill in the gaps
- A70%
- B30%
21Fill in the blanks
- AK
- BImposition of limits
22Fill in the blanks
- AFully exploited
- B10%
23Fill in the blanks
- AIntrinsic rate of population increase
24Fill in the blanks
- AAdriatic Sea
25Fill in the blanks
- AAtlantic Cod
26Fill in the blanks
- APopulation growth rate
27Fill in the blanks
- AMaximum growth rate
- BMaximum sustainable yield
28Fill in the blanks
- Aautomatic Identification system
29Fill in the blanks
- AVessel monitoring system
30Fill in the blanks
- A0.1
Information
- Description
- Human interactions and Fisheries
- Author
- Ethan Ross
- Language
- English
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- 76
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