Carlotta Molfese & Jason Hall-Spencer 2015 Fishing Down the Food Chain
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Overfishing and the replacement of demersal finfish by shellfish: an example from the English Channel Carlotta Molfese & Jason Hall-Spencer Plymouth University South West Marine Ecosystems 2015
Carlotta Molfese & Jason Hall-Spencer 2015 Fishing Down the Food Chain
Reports from the front line of the current mass extinction: ocean acidification, fisheries and ecocideCarlotta Molfese & Jason Hall-SpencerMarine Biology and Ecology Research Centre, Plymouth UniversityE: [email protected][email protected] the 1950s there has been a human population explosion with widespread coastal habitat damage exacerbated by our ever increasing use of hydrocarbon reserves. Within the past 100 years fishing using internal combustion engines has completely changed the ecology of coastal waters, it has damaged nursery areas and homogenised seabed habitats. We have also fished-down coastal food-webs, removing large long-lived fish (like cod and hake) to the benefit of invertebrates (like scallops and cuttlefish). Despite this marine ecocide, we can turn things around. Evidence of the widespread damage caused to cold-water coral reefs by trawls in 2002, forced governments to take action. Several High Seas and EU closures are now in force and satellite vessel tracking data indicate that they are working effectively, with good compliance by international fleets.A key solution to securing Good Environmental Status is obvious: reduce the footprint of the most destructive practices to allow recovery of coastal systems but attention has recently turned to the question of whether these efforts can really work, given that the temperature, chemistry and biology of the oceans is changing rapidly. Underwater CO2 vents show why we need to factor acidification and warming into marine management plans and provide realistic insights on which flora and fauna are able to thrive in high CO2 environments, forewarning those people that are reliant on aquaculture, fisheries and coastal tourism. This talk uses case studies on inshore fisheries, deep-water coral reefs and ocean acidification to show that we have our work cut out if we are to achieve ‘Good Environmental Status’ anytime soon. But, if we are sensible, we can limit on-going damage.https://theconversation.com/profiles/jason-hall-spencer-131492/articlesHall-Spencer JM, Tasker M, Soffker M, Christiansen S, Rogers S, Campbell M, Hoydal K (2009) The design of Marine Protected Areas on High Seas and territorial waters of Rockall. Marine Ecology Progress Series 397, 305-308Jackson EL, Davies A, Howell KL Kershaw PJ Hall-Spencer JM (2014) Future-proofing Marine Protected Area networks for cold water coral reefs. ICES Journal of Marine Science. doi: 10.1093/icesjms/fsu099Molfese C, Beare D, Hall-Spencer JM (2014) Overfishing and the replacement of demersal finfish by shellfish: an example from the English Channel. PLoS ONE 9(7), e101506.
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Overfishing and the replacement of demersal finfish by
shellfish: an example from the English ChannelCarlotta Molfese
& Jason Hall-Spencer
Plymouth University
South West Marine Ecosystems 2015
Scallop dredges and trawls alter the seabed; scallops are
resilient but many long-lived organisms (e.g. maerl) are not
Satellite data show the large area affected by modern heavy gear
types in the English Channel
a
Footprint of a) UK scallop dredgers and b) beam trawlers >15
m length (Campbell et al. 2014 Marine Policy)
b
Pauly et al. (1998): Fishing Down Marine Food Webs
o mean Trophic Level of global fisheries landings declining
o NW Atlantic cod shrimps, crabs, lobsters
o Firth of Clyde finfish Nephrops and scallops
Current study
90-year English Channel landings dataset
Is there a Fishing down trend in the English Channel?
Have there been major changes in species landed?
Catch composition
GadoidsCod (Gadus morhua)
Ling (Molva molva)
Hake (Merluccius merluccius)
Landings now low
We import them to meet demand
Catch composition
InvertebratesEdible crab (Cancer pagurus)
Lobster (Hommarus gammarus)
Scallop (Pecten maximus)
0
1000
2000
3000
4000
5000
6000
7000
8000
1920 1930 1940 1950 1960 1970 1980 1990 2000 2010
Lan
din
gs (t
)
Time (yr)
D Cuttlefish (Sepia officinalis)
Shellfish (e.g. scallops) now more prevalent in Channel
landings.
Landings and trophic level
There were more big fish before widespread use of heavy towed
gear
We need to ensure that measures we put in place are not
maladaptive
Electric pulse fishing by the Dutch fleet
Electric pulse lab. tests cause significant increases in viral
infections in shrimp (Crangon crangon) and severe injuries in cod
(Rinsjorp pers. comm)
Its not too late to turn things around
Technology that puts marine life at risk can be used to protect
it
Demersal gear closures that maximize habitat protection and
minimize fisheries displacement
We know we are causing the current planetary mass extinction
what survives will depend on how sensible we are in protecting the
resources we still have.
Because there have been far fewer extinctions in the oceans, we
still have the raw ingredients needed for recovery.
Remove damaging practices to allow nature to rebound under an
economic model that values environmental quality as well as
continued ocean use.
