Date post: | 23-Dec-2015 |
Category: |
Documents |
Upload: | gyles-mccoy |
View: | 214 times |
Download: | 0 times |
Noëlle BRU Laboratoire de Mathématiques et ses Applications
UMR CNRS 5132 Université de Pau et des Pays de l’Adour
Patrick PROUZETIFREMER LRHA
Michel LEJEUNEUniversité Grenoble 2
As an example the Adour Estuary (Southwestern part of France)
About management groups : ICES (International Council for the Exploration of the sea): “the stock of
European eel (Anguilla Anguilla L.) is outside safe biological limit and that current fisheries are not sustainable”.
18 September 2007: the Council of the European Union adopted a council regulation (EC 1100/2007) establishing measures for the recovery of stock of European eel.
November 2007 : the IUCN (International Union for Conservation of Nature) listed the European eel on its Appendix II and considered the eel as an endangered species.
Glass eel = young eel... Passive migration… During flood tide… Mainly by night…
Colloque ASP - Boulogne sur Mer 2008 2
General context…General context…
(source : IFREMER)
Colloque ASP - Boulogne sur Mer 2008 3
In European estuaries: constant decrease is observed for several years.
Over-exploitation at the different phases of the biological cycle ?
Inland habitat loss ?Climate and ocean current changes ?
Diseases ? Degradation of continental environment and pollution ?…
General context…General context…
??
Colloque ASP - Boulogne sur Mer 2008 4
• Most methods : » Designed for a fixed stock within a given area » Geostatistical approaches» Hydroacoustics campaigns…
• A specific method : in a particular environment : from the mouth of a estuary + an area of migration ... a species with a specific migratory behavior... a method to compute an efficient estimate of glass eels abundance...
Problems…Problems…
Colloque ASP - Boulogne sur Mer 2008 5
Used to propose biomass estimates…
How and why to put together these datasets ??
About the talk...About the talk...
What are the data available to do so ?
Historical time series of professional catches
(by day, into the maritime area)
Data from scientific in situ surveys
Step 1
Step 2
Are they really good indicators of abundance ?
Step 1 of the method :
Using data from scientific in situ surveys…
Step 1 : In situ scientific surveys…
• Sampling protocol and data
• Statistical method for estimation of « observed » glass eels biomass
• Results and discussion
Step 2 : Using professional catches…• Estimate of seasonal glass eels
biomass migrating by night • Estimate of glass eels recruitment
•
« Observed » glass eels biomass estimates(source IFREMER)
Colloque ASP - Boulogne sur Mer 2008 7
All samples are assumed to be simultaneous... -9
-8
-7
-6
-5
-4
-3
-2
-1
0
1 passage 30 min( 8 passages max !!!)
…… during the flood tide….
5 min 5 min 5 min
10 min
Right Bank Middle Left Bank
Glass eel densities(in g/100m3)
ks td
s=1…S (=6) k=1,…, n(=8)
Main Push-sieve fishery
Step 1 : In situ scientific surveys…
• Sampling protocol and data
• Statistical method for estimation of « observed » glass eels biomass
• Results and discussion
Step 2 : Using professional catches…• Estimate of seasonal glass eels
biomass migrating by night • Estimate of glass eels recruitment
•
The Adour estuary
Colloque ASP - Boulogne sur Mer 2008 8
R
t
t
s dtdstBRB2
1
J
j
S
ssj
t
t ss SdttvtdJ
RB1 1
2
1
1
J
j
S
ssj
t
t s SdttBJ
RB1 1
2
1
1
Total biomass (in kg)for the flood tide period
through vertical region R
sB̂ jB̂ RB̂
Step 1 : In situ scientific surveys…
• Sampling protocol and data
• Statistical method for estimation of « observed » glass eels biomass
• Results and discussion
Step 2 : Using professional catches…• Estimate of seasonal glass eels
biomass migrating by night • Estimate of glass eels recruitment
•
J different schemes tested…
Colloque ASP - Boulogne sur Mer 2008 9
2
1
ˆˆˆ t
t sss dttvtdB
tvftd ss
We need a functional form for each term!!
Step 1 : In situ scientific surveys…
• Sampling protocol and data
• Statistical method for estimation of « observed » glass eels biomass
• Results and discussion
Step 2 : Using professional catches…• Estimate of seasonal glass eels
biomass migrating by night • Estimate of glass eels recruitment
•
For the current speed vs(t)…
A sinusoidal model depending on time
A log-log linear model depending on the current
speed
For glass eels density ds(t)…
An explicit form for the estimate
+An evaluation of its
variability
• to correct possible errors of measurement• to evaluate the beginning and the end of the flood tide
Finally,◦ Simple method... With sparse data...◦ Some approximations and hypothesis…◦ More surveys than results...◦ But “observed” biomasses seems
“realistics” !
Method easily adaptable for other estuaries
Exploitation rates for push-sieve are derived by days...
Colloque ASP - Boulogne sur Mer 2008 10
Step 1 : In situ scientific surveys…
• Sampling protocol and data
• Statistical method for estimation of « observed » glass eels biomass
• Results and discussion
Step 2 : Using professional catches…• Estimate of seasonal glass eels
biomass migrating by night • Estimate of glass eels recruitment
• Season Day Biomass (in Kg) push-sieve catches (in Kg)
98/99
12/01/1999 138 6
14/01/1999 379 8,2
22/01/1999 157 11,2
28/01/1999 42 4,5
11/02/1999 79 4,6
17/02/1999 206 14,5
17/03/1999 203 13,5
99/00
09/12/1999 1597 36,79
22/12/1999 664 21,15
05/01/2000 409 77,31
07/01/2000 821 63,64
08/01/2000 763 34,67
09/01/2000 993 12,56
12/01/2000 95 8,79
01/02/2000 1715 36,18
08/02/2000 464 1,2
00/01
14/12/2000 152 3,2
21/12/2000 134 14,7
03/01/2001 28 3
10/01/2001 97 11,5
12/01/2001 81 18,1
24/01/2001 264 64,5
26/01/2001 132 45,9
02/0303/01/2003 55 30,4
22/01/2003 82 2,6
03/0426/11/2003 80 8,2
21/01/2004 37 8,2
04/05
09/11/2004 550 10,3
18/11/2004 257 33,8
23/11/2004 37 1,5
08/12/2004 375 13
14/12/2004 198 17,6
Step 2 of the method :Using both information (« observed » estimates and professional catches)
Estimate of seasonal glass eels biomassmigrating by night
Estimate of glass eels recruitment for a fixed fishing season
Step 1 : In situ scientific surveys…
• Sampling protocol and data
• Statistical method for estimation of « observed » glass eels biomass
• Results and discussion
Step 2 : Using professional catches…• Estimate of seasonal glass eels
biomass migrating by night • Estimate of glass eels recruitment
•
Colloque ASP - Boulogne sur Mer 2008 12
Evolution des captures professionnelles en zone maritime et des biomasses journalières estimées lors des campagnes scientifiques in situ .
0
200
400
600
800
1000
1200
1400
1600
1800
27/10/1999 16/11/1999 06/12/1999 26/12/1999 15/01/2000 04/02/2000 24/02/2000 15/03/2000
Saison 1999/2000
TOTTAM (en kg) Biomasse (en kg)
Model ? Dependent variable : rate of exploitationExplanatory variables : catches
+ environmental variables
Step 1 : In situ scientific surveys…
• Sampling protocol and data
• Statistical method for estimation of « observed » glass eels biomass
• Results and discussion
Step 2 : Using professional catches…• Estimate of seasonal glass eels
biomass migrating by night • Estimate of glass eels recruitment
•
Professional catches with push-sieves
« observed » biomass
Data concerning the same glass eel run !!
Model : glm( Rate ~ TurbCod + Catches^0.646 + TideCod+
FlowCod * Moon+catches*Moon)
◦ Gamma distribution (with canonical link = inverse)◦ Coded explanatory variables :
Colloque ASP - Boulogne sur Mer 2008 13
Step 1 : In situ scientific surveys…
• Sampling protocol and data
• Statistical method for estimation of « observed » glass eels biomass
• Results and discussion
Step 2 : Using professional catches…• Estimate of seasonal glass eels
biomass migrating by night • Estimate of glass eels recruitment
•
TurbCod TideCod FlowCod
1 if <13 NTU 2 otherwise.
1 if <60, 3 > 86 2 otherwise
1 if <250 m3/s, 3 > 400 m3/s 2 otherwise
Degree of
freedom Deviance
Residual Degree of freedom F value Pr(F)
NULL 31
TurbCod 1 9,572 30 18,746 0,001
Catches^0,678 1 3,185 29 6,237 0,024
TideCod 2 0,939 27 0,919 0,419
FlowCod:Moon 8 7,044 19 1,724 0,168
Catches:Moon 3 1,295 16 0,845 0,489
With 32 observations…
Colloque ASP - Boulogne sur Mer 2008 14
« cleaned » values
+ A variability associated to each predicted
value of the rate of exploitation !
Step 1 : In situ scientific surveys…
• Sampling protocol and data
• Statistical method for estimation of « observed » glass eels biomass
• Results and discussion
Step 2 : Using professional catches…• Estimate of seasonal glass eels
biomass migrating by night • Estimate of glass eels recruitment
•
Values >100 or < 0
Predicted rate of exploitation <1,5% and catches >100kg
tide < 60 and rate of flow >600m3/s
Colloque ASP - Boulogne sur Mer 2008 15
Nov Dec Jan Feb1999 2000
10
00
20
00
30
00
40
00
50
00
60
00
*
* ****
*
*
*
Biomasse estimée sur certains joursBiomasse extrapolée sur la saisonBiomasse observée
Smoothed biomass (by gaussian kernels)
Predicted biomass + erreur
« observed » biomass + error of prediction
Step 1 : In situ scientific surveys…
• Sampling protocol and data
• Statistical method for estimation of « observed » glass eels biomass
• Results and discussion
Step 2 : Using professional catches…• Estimate of seasonal glass eels
biomass migrating by night • Estimate of glass eels recruitment
•
T97ˆ nightB
With a estimated standard error around 7 T
Colloque ASP - Boulogne sur Mer 2008 16
+Glass eels recruitment for a fixed season ???
Known for every night (see before) unknown
Hyp : mean value between two consecutive nights
Fishing season
Catckes with push-sievesin kg
Total catchesin kg
Biomass
in kg
Rate of exploitation
of push-sieves
Glass eels recruitment
in kg
Overall rate of exploitation
1998/1999 1,655 ~ 6,000 28,200 5.9% 53,478 11.2%
1999/2000 4,579 ~15,000 96,900 4.7% 181,354 8.3%
2000/2001 1,446 1,983+F 15,500 9.3% 32,990
2001/2002 770 2,395+F 20,600 3.7% 43,307
2002/2003 388 0,594+F 3,100 12.5% 6,231
2003/2004 1,093 2,969 8,700 12.6% 17,550 16.9%
2004/2005 1,398 7,183 27,700 5.0% 59,292 12.1%
2005/2006 686 3,531 7,870 8.7% 15,719 22.4%
average 1,502 26,070 7,85% 51,240
median 1,246 18,050 7,3% 38,149
Step 1 : In situ scientific surveys…
• Sampling protocol and data
• Statistical method for estimation of « observed » glass eels biomass
• Results and discussion
Step 2 : Using professional catches…• Estimate of seasonal glass eels
biomass migrating by night • Estimate of glass eels recruitment
•
Need to explicit the precision of each estimates at each step of the calculus.
The method is adaptable to other estuary but with the search of a model…
But the level of seasonal biomass is realistic !!
Colloque ASP - Boulogne sur Mer 2008 17
Conclusions and Conclusions and perspectives…perspectives…
Colloque ASP - Boulogne sur Mer 2008 18
Thanks to the numerous scientists and crew members who conducted the experimental campaigns because our analysis is based on their hard work !!!