Noëlle BRU Laboratoire de Mathématiques et ses Applications UMR CNRS 5132 Université de Pau et...
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Transcript of Noëlle BRU Laboratoire de Mathématiques et ses Applications UMR CNRS 5132 Université de Pau et...
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 !!!