Spatial management and cod recovery

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Spatial management and cod recovery
M. J. Kaiser School of Ocean Sciences, University
of Wales, Bangor
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Spatial management in relation to key
life-history bottle-necks
Useful for juvenile and adult stages
if associated with habitat/area
Not useful for eggs and larvae
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Stock movements water
source GLOBEC
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Stock dynamics- at a finer scale
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Evidence for stock structure- from mark-recapture
experiments
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Implications for scale of networks of spatially
managed areas
Network for entire North Sea
Network within the sub-population
ILLUSTRATIVE ONLY!!!!!!
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Using spatial management to mitigate the effects
of fishing on habitat critical to particular
life-history stages Is spatial management better
than effort reduction?
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Acute impacts of fishing gear a global
analysis Meta-analysis of 101 different fishing
impact manipulations. The direct
effects of different types of fishing gear were
strongly habitat-specific.
No change
Habitat type (gravel, sand, mud)
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Trawling impact on nematodes
lt 1mm, live in the sediment Very
abundant Contribute about 50 of total benthic
production
Effects of trawling more pervasive than
previously considered
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Chronic bottom trawling alters the functional
composition of benthic invertebrate communities
on a sea basin scale
Consistent decrease in abundance of permanently
attached biota and filter feeders. May cause
breakdown of energy flow to bottom ecosystems
(Choi et al. 2004 Can. J. Fish. Aquat. Sci.)
Changes in function and processes Habitat Prey
resources Flow of energy between seabed and water
column Regime shift to pelagic dominated
system (e.g. jellyfish or herrings)
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Application and evaluation of spatial
planning Marine Protected Areas - MPAs Closed
areas result in redistribution of fishing
effort Impact of area closures on biomass and
production benthic communities
Open area
Open area
Open area
MPA
Medium
Medium
None
Heavy
Trawling
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MPA
Removal of effort slow recovery Relocation of
effort negative effect on benthic biomass and
production
Remains open
Without effort reduction, MPAs only have a minor
(positive or negative) impact on overall benthic
ecosystems.
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Habitat sensitivity classes
Recovery time
0-1 y shallow,
1-2 y high tidal currents
2-4 y
4-7 y deep areas,
gt7 y low current and waves
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Gear restrictions can produce similar results to
MPAs
This fishery area is c. 500 km²
Devon, UK
Static gear.
Static Jul - Jan.
Static Apr - Dec.
Static Sept - Jan.
Static Sept - Mar.
No towed gears.
English Channel / La Manche
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Secondary effects of fishing on fecundity
Greater abundance and biomass of scallops in
protected areas, but more importantly bigger
gonads for animals of the same size
But scallops do not move 100s km as adults
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Fisheries benefits of MPAs - what scale is
appropriate in temperate systems?
- Small short-lived species with limited ranges
benefit from protection. - Large bodied,
longer-lived species do not benefit from
protection at this scale
Year
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And then there are the unforeseen effects..
Ecological impact of the plaice box Gear
restriction area (MPA) Only small trawlers,
effort in box reduced gt90. Effort outside box
increased Aim to reduce the bycatch of
undersized plaice in a nursery ground.
North Sea
Ineffective Juvenile plaice have moved out of
plaice box after implementation
Plaice box
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Plaice eat small worms Trawling Total
production down / small worm production - up
Juvenile plaice may have followed their food to
the trawled areas MPAs are not suitable
for all fish species Suitability depends on
ecology of the species (what do they eat,
migrations, etc.)
Hilmar Hinz
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Understanding the wider implications of spatial
management

• Fisheries economic hotspots around the coast of
  Wales
• Some areas very important, others almost
  insignificant to the fishery

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Results marine reserve networks
Coarse resolution (DEFRA)
Area-minimising

0.38 (most similar)

0.19
Biodiversity
Fine resolution
0.11 (least similar)


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Predicted fishery losses
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Acknowledgements Simon Jennings Paul Hart Heidi
Tillin Gareth Edwards-Jones Trevor Hutton Bob
Clarke Gerjan Piet Mel Austen Adriaan
Rijnsdorp James Forde Hilmar Hinz Rob
Blyth-Skyrme Paul Somerfield Ana Queiros I
Karakassis Daniel Duplisea