Fishing impact on fish communities
-
Upload
joan-moranta -
Category
Education
-
view
164 -
download
1
description
Transcript of Fishing impact on fish communities
Fishing impact on fish communities:
What does biomass (or size) tell us?
Spanish Institute of OceanographyPalma de Mallorca, Balearic Islands, Spain
School of Ocean ScienceMenai Bridge, Anglesey, UK
Joan Moranta
Thesis: Deep western Mediterranean demersal fish communities
Contents :
1.Introduction
2.Three examples of the fishing impact on fish communities
2.1. Large bathymetric range (200-1800m)
Moranta et al. (1998). Marine Ecology Progress Series 171, 247-259.
Moranta et al. (2004). Scientia Marina 68, 141-152.
2.2. Large spatial scale (1200 km)
Moranta et al. (2007). Progress in Oceanography 72, 63-83.
2.3. Short temporal scale (seasons)
Moranta et al. (2008). Journal of Marine Systems 71, 346-366.
3.Conclusions
Fishing impact on fish communities:
What does biomass (or size) tell us?
1. Introduction: Effects of fishing impact on fish communities
Biomass, and Size Structure
Modification
1. Introduction: Something to compare with (CONTROL)
The Baseline Scenario Pristine Ecosystem
Few ‘unfished’ control sites are now available for study, and these are at the scale of small areas such as individual reefs rather than ecosystems (Jennings & Kaiser 1998)
Absence of FishingMarine Reserves
↑ Number of species
↑ Abundance of species
↑ Sizes at shallow depth
2. Examples: 2.1. Large bathymetric range (200-1800 m)
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 538
38.5
39
39.5
40
Mallorca
Menorca
Eivissa
Algeriana subbasin2000
800
1000
600
400
Formentera
400
1000
2000
40.5
41
41.5
42
South of the Balearic Islands
0 m
100 m
200 m
300 m
400 m
500 m
600 m
700 m
800 m
> Bottom trawl fishery banned beyond 1000 m depth
Continental Shelf
Upper Slope
European Hake
(Merluccius merluccius)
Norwey Lobster (Nephorps norvegicus)
Red Shrimp (Aristeus antennatus)
Red Mullet
(Mullus surmuletus)
Example 2.1 Large bathymetric range (200-1800 m)
Wide distribution range:
P. blennoides, G. melastomus, N. aequalis,
A. rostratus
T. minutusC. maculatusA. laternaA. rueppelliP. cataphractumS. caniculaH. dactylopterusG. argenteusM. dipterygia T. lyraL. bosciiM. merlucciusC. caelorhincus S. nigrescensS. phaetonE. denticulatusS. elongataL. caudatusC. agassizii P. blennoidesL. budegassaM. poutassouG. melastomusA. megalokinodonH. mediterraneusH. italicusS. ligulatusD. lichaC. congerE. spinaxT. scabrusE. telescopusN. bonaparteiN. aequalisM. moroN. melanurumC. alleniA. rostratusL. lepidionC. labiatusP. rissoanusB. mediterraneusC. coelolepisCh. mediterraneaC. guentheriL. guentheri
1 2 3 4 5 6 7 8
200 400 600 800 1000 1200 1400 1600 1800
O O O O O O O O
0.00
1.00
1
2
3
4
%
Sim
ilaity
10
0
% S
imila
ity1
00
200-400m 400-800m 800-1400m 1400-1800 m
Example 2.1 Large bathymetric range (200-1800 m)
Bathymetric distribution of fish community descriptors
Linear regression y=19.73-0.008x (r2 =0.74;P<0.001)
0
5
10
15
20
25
200 400 600 800 1000 1200 1400 1600 1800
Depth (m)
Sp
eci
es
rich
ne
ss
Logarithmic regression y=132.3-18.4Ln(x) (r 2 =0.39;P<0.001)
0
20
40
60
80
100
200 400 600 800 1000 1200 1400 1600 1800
Ab
un
da
nce
/10
00
m2
Polynomial regression y=-137.7+1.4x-0.0007x 2
(r 2 =0.22, P<0.05)
0
200
400
600
800
1000
1200
200 400 600 800 1000 1200 1400 1600 1800
Depth (m)
Bio
ma
ss/1
00
0m
2
Polynomial regression y=-237.8+0.81x-0.0004x (r =0.69; P<0.001)
0
100
200
300
400
500
0 200 400 600 800 1000 1200 1400 1600 1800
Me
an
Fis
h W
eig
ht/
10
00
m2
2
2
Depth (m)Depth (m)
Example 2.1 Large bathymetric range (200-1800 m)
Norm
alis
ed B
iom
ass
Spect
ra (
%)
Biomass Size Class (log2 g)
Upper Slope (200-800 m)
Middle Slope (800-1400 m)
Lower Slope (1400-1800 m)
05
1015
20253035
0
5101520
253035
0 2 4 6 8 10 120
51015
20253035
Example 2.1 Large bathymetric range (200-1800 m)
Council Regulation, EC Nº 1967/2006 of 21 December 2006: prohibition of bottom trawl fishing below 1000 m depth (as precautionary measure, because trawl fleet have not yet explored these grounds)
Mean F
ish W
eig
th (
g)
Mean M
axum
um
FW
(g)
Depth (m)
0
50
100
150
200
250
300
200 400 600 800 100012001400160018000
100
200
300
400
500
FishingImpact
Absence of Fishing
FishingImpact
MEDITS Surveys: 1994-2000 200-800 m
42
41
40
39
38
37
36
35
3210º12345
Cap de Creus
1000 m
SECTOR C (60%)
SECTOR B (29%)
SECTOR A (11%)
Capde Gata
Cap de Palos
PuntaEuropa
MEDITS Surveys
Illes Balears
200 m
Cap Salou
Delta de l´Ebre
Cap de San Antoni
Illa d´Alboran
2. Examples: 2.2. Large spatial scale (1200 km)
Caelorhinchus caelorhinchus
Hymenocephalus italicus
Nezumia aequalis
Trachyrinchus scabrus
S-C (6
0)
S-B (2
9)
S-A (11)
Example 2.2 Large spatial scale (1200 Km)Caelorhinchus caelorhincus
-1 0 1 2
0.0
0.5
1.0
1.5
2.0
2.5
3.0
Hymenocephalus italicus
-1 0 1 2
0.0
0.5
1.0
1.5
2.0
2.5
3.0
Nezumia aequalis
-1 0 1 2
0.0
0.5
1.0
1.5
2.0
2.5
3.0
Trachyrinchus scabrus
PCA-Axis I
-1 0 1 2
0.0
0.5
1.0
1.5
2.0
2.5
3.0
-1 0 1 20.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
-1 0 1 20.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
-1 0 1 20.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
-1 0 1 2
L
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
-1 0 1 2
0.00.20.40.60.81.01.21.4
-1 0 1 2
0.00
0.02
0.04
0.06
0.08
-1 0 1 2
0.0
0.20.4
0.6
0.8
1.01.21.4
-1 0 1 2
0.0
0.5
1.0
1.5
2.0
2.5
Log
10 (
Ab
un
.)Lo
g1
0 (
Ab
un
.)Lo
g1
0 (
Ab
un
.)Lo
g1
0 (
Ab
un
.)
Log
10 (
Bio
m.)
Log
10 (
Bio
m.)
Log
10 (
Bio
m.)
Log
10 (
Bio
m.)
Log
10 (
MFW
.)Lo
g1
0 (
MFW
.)Lo
g1
0 (
MFW
.)Lo
g1
0 (
MFW
.)
β=-0.54 β=-0.49 β=-0.27
β=-0.73 β=-0.63 β=-0.30
β=-0.40
β=-0.52
PCA-Axis I PCA-Axis I
Log
10 (
Abundance
)Lo
g10 (
Abundance
)
Log10 (Body mass) Log10 (Body mass)
S-C (6
0)
S-B (2
9)
S-A (11)
Example 2.2 Large spatial scale (1200 Km)
Caelorinchus caelorhinchus
-2 -1 0 1 2 3
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
Nezumia aequalis
-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5Trachyrinchus scabrus
-2 -1 0 1 2 3
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
Himenocephalus italicus
-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
Sector CSector BSector A
Pre-anal Length (cm)
Sector C (1000-1400 m)
Perc
en
atg
ePerc
en
tage
Example 2.2 Large spatial scale (1200 Km)
S-C (6
0)
S-B (2
9)
S-A (11)
Nezumia aequalis
0 1 2 3 4 5 6 70
5
10
15
20
25
Sector C
Trachyrinchus scabrus
0 2 4 6 8 1012141618 20220
2
4
6
8
10
12
14
Nezumia aequalis
0 1 2 3 4 5 6 70
10
20
30
40
50
Sector A
Trachyrinchus scabrus
0 2 4 6 8 1012141618 20220
5
10
15
20
25
30
35
Sector B
Pre-anal Length (cm)
Pre-anal Length (cm) Pre-anal Length (cm)
Sector A, B, C (200-800 m)
Cabrera
Sóller
31 FV
Year Target species Effort (days)
Cabrera Sóller
European Hake 417 504 2003
Red Shrimp 829 2549
European Hake 420 334 2004
Red Shrimp 774 2499
S'0
3O
'03
N'0
3D
'03
J'04
F'0
4M
r'04
Ap'
04M
y'04
Jn'0
4Jl
'04
Ag'
04S
'04
O'0
4
Fis
hing
day
s
020406080
100120140160180200
Cabrera Sóller
2. Examples: 2.3. Short temporal scale (Seasons)
Fishing Period 1: from May to Sep.
Higher fishing effort at SO
Fishing Period 2: rest of the year.
Similar fishing effort at both
locations
Fishing Period 1: from May to Sep. Higher fishing effort at SO
Fishing Period 2: rest of the year. Similar fishing effort at both locations
ElasmobranchesPeriod 1 Period 2
Body mass (log2) Body mass (log2)
Cabrera Sóller
1 2 3 4 5 6 7 8 9 10 11 126
8
10
12
14
16b=0.77; a=6.63; r 2=0.72; F=15.45*
b=-0.25; a=9.43; r 2=0.16; F= 1.11
1 2 3 4 5 6 7 8 9 10 11 126
8
10
12
14
16b=0.64; a=7.02; r 2=0.77; F=19.85*
b=0.23; a=8.31; r 2 =0.12; F=0.85
CA
SO
Example 2.3 Short temporal scale (seasons)
NB
S (
log
2)
500 - 800 m
Example 2.3 Short temporal scale (seasons)
GL: Blackmouth catshark (Galeus melastomus)RoE: Rest of ElasmobranchsAA: Red shrimp (Aristeus antennatus)RoDC: Rest of Demersal CrustaceansPB: Greater forkbeard (Phycis blennoides)RoDT: Rest of demersal teleosts
Bathymetric range: 500-800 m
Fishing Period 1: from May to Sep. Higher fishing effort at SO
Fishing Period 2: rest of the year. Similar fishing effort
CA
SO
1. Population size-based metrics and biomass spectra are good predictors of fishing effects. Thus, higher biomass and body size values for some dominant and subdominant fishes from the upper slope are associated with lower levels of fishing exploitation.
2. In areas intensively exploited by the trawl fishery, such as the upper slope of the western Mediterranean, the impact of this exploitation has an effect on the species traits, since it influences the distribution, abundance and biomass of fishes at the local and mesoscale levels.
3. The knowledge derived from unexploited fish communities on the middle and lower slope, as well as a comparison between areas with different fishing exploitation rates on the upper slope, can be used as a baseline for assessing and managing fisheries impacts in the context of an ecosystem-based approach to fisheries, which can help to set indicator reference levels.
3. Conclusions:
Tkanks for your attention