Assessing fishing and marine biodiversity changes using fishers' perceptions: the Spanish Mediterranean and Gulf of Cadiz case study.
BACKGROUND
The expansion of fishing activities has intensively transformed marine ecosystems worldwide. However, available time series do not frequently cover historical periods.


METHODS
Fishers' perceptions were used to complement data and characterise changes in fishing activity and exploited ecosystems in the Spanish Mediterranean Sea and Gulf of Cadiz. Fishers' interviews were conducted in 27 fishing harbours of the area, and included 64 fishers from ages between 20 to >70 years old to capture the experiences and memories of various generations. Results are discussed in comparison with available independent information using stock assessments and international convention lists.


RESULTS
According to fishers, fishing activity substantially evolved in the area with time, expanding towards deeper grounds and towards areas more distant from the coast. The maximum amount of catch ever caught and the weight of the largest species ever captured inversely declined with time. Fishers (70%) cited specific fishing grounds where depletion occurred. They documented ecological changes of marine biodiversity during the last half of the century: 94% reported the decline of commercially important fish and invertebrates and 61% listed species that could have been extirpated, with frequent mentions to cartilaginous fish. Declines and extirpations were in line with available quantitative evaluations from stock assessments and international conventions, and were likely linked to fishing impacts. Conversely, half of interviewed fishers claimed that several species had proliferated, such as cephalopods, jellyfish, and small-sized fish. These changes were likely related to trophic cascades due to fishing and due to climate change effects. The species composition of depletions, local extinctions and proliferations showed differences by region suggesting that regional dynamics are important when analysing biodiversity changes.


CONCLUSIONS
Using fishers' perceptions, fishing and ecological changes in the study area were documented. The recovery of local ecological knowledge provides valuable information complementing quantitative monitoring and evaluation surveys.
Institut de Ciències del Mar (ICM-CSIC). Barcelona, Spain ; UMR EME 212 Centre de Recherche Halieutique Méditerranéenne et Tropicale. IRD - IFREMER & Université Montpellier II. Sète Cedex, France.
Marta
M
Coll
OCEANA, Madrid, Spain.
Marta
M
Carreras
Investigación, Planificación y Desarrollo S.A., Madrid, Spain.
Cristina
C
Ciércoles
OCEANA, Madrid, Spain.
Maria-José
MJ
Cornax
Institut de Ciències del Mar (ICM-CSIC). Barcelona, Spain.
Giulia
G
Gorelli
Universidad de Almería (UAL). Almeria, Spain.
Elvira
E
Morote
Institut de Ciències del Mar (ICM-CSIC). Barcelona, Spain.
Raquel
R
Sáez
D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D000818:Animals; D001267:Atlantic Ocean; D044822:Biodiversity; D057231:Climate Change; D003247:Conservation of Natural Resources / Q000379:methods / Q000706:statistics & numerical data; D017753:Ecosystem; D005398:Fisheries / Q000379:methods* / Q000706:statistics & numerical data; D005399:Fishes / Q000145:classification / Q000254:growth & development*; D005843:Geography; D006801:Humans; D008522:Mediterranean Sea; D008875:Middle Aged; D010465:Perception; D011156:Population Density; D011157:Population Dynamics; D012623:Seawater; D013030:Spain; D011795:Surveys and Questionnaires; D013997:Time Factors; D055815:Young Adult