Test
Human interactions and Fisheries
Este test tiene tipos de pregunta que se abren en el reproductor de siempre.
Preguntas del test (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
Información
- Descripción
- Human interactions and Fisheries
- Autor
- Ethan Ross
- Idioma
- English
- Visitas
- 76
- Etiquetas
- Valoración
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