Considered a single stock: No
The Working Group considers each of the two species of sardinella in the subregion to constitute single stocks, covering the whole subregion. Further details on stock identity can be found in an earlier report of the Working Group (FAO, 2001).
In Zone C to the north of Cap Blanc, sardinella is exploited by a fleet of Moroccan purse seiners and by industrial trawlers from the Russian Federation, and the European Union.
In Mauritania, sardinella is exploited by long-distance trawlers from the EU and other countries, by some small purse seiners, and by an artisanal fleet of canoes that originate not only from Mauritania but also from Senegal. Some of the Senegalese canoes operate in the southern part of Mauritania and land their catches in Saint Louis. These catches are included in the Senegalese landing figures. Other Senegalese canoes work under charter for fish meal factories and a fish processing plant in Nouadhibou. Finally there is a group of Senegalese canoes that operate from Nouakchott and that land sardinella for human consumption. The industrial fleet in Mauritanian waters can be divided in two segments: the Dutch-type fleet (trawlers from the Netherlands, France, UK, Germany and Lithuania) and the Russian-type fleet (all from Eastern European origin). This division is based on the fact that the Dutch-type fleet targets sardinella, whereas the Russian-type fleet targets horse mackerel and mackerel, and take sardinella only as secondary species.
In Senegal, sardinella is exploited by the artisanal fleet, and to a much lesser extent by a small industrial fleet. The main fishing gears used in the artisanal fleet are the purse seine and the surrounding gillnet. In 2011 there was also a fishery by Russian trawlers in Senegal (see below). Total catches
Total catches of Sardinella aurita
and Sardinella maderensis
by fleet and by country are given in Table 3.2.1a and Table 3.2.1b respectively. Total catches for each species for the subregion are presented in Figures 3.2.1a and b.
In Morocco, the national fleet in Zone C more than doubled its catch of S. aurita
from 25 178 tonnes in 2010 to 65 985 tonnes in 2011. This catch consisted entirely of juvenile S. aurita
In Mauritania, the total catch of sardinella decreased from 332 449 tonnes in 2010 to 229 244 tonnes in 2011. This catch as usual consisted predominantly of S. aurita
(91%). The decline in catch occurred in the Dutch-type fleet (-36%) and in the artisanal feet (-47%). In contrast, catches in the Russian-type fleet increased (+33%).
In Senegal, total catches of sardinella in the artisanal fleet showed an increase from 281 734 tonnes in 2010 to 323 915 tonnes in 2011 (+15%). The catch in 2011 consisted of 72 percent for S. aurita
and 28 percent for S. maderensis
. The catch in the Senegalese industrial fleet was 1 767 tonnes in 2011; an increase of 2 percent over 2010. This year for the first time a fleet of Russian trawlers worked in Senegal. They took a total of 6 976 tonnes of sardinella, 57 percent of which was S. aurita
In The Gambia, the total catch of sardinella was 7 780 tonnes in 2011, which was a decrease of 1 percent from 2010. Sardinella aurita
made up 36 percent of the catch, and S. maderensis
64 percent. Sardinella aurita
The total catch of S. aurita
for the whole subregion was estimated at 600 332 tonnes in 2011. This was an increase over the already very high level of the previous three years, and it constituted a record for the period for which the Working Group has collected statistics (1990–2011). The increase in catch occurred in all countries of the subregion, except for Mauritania.Sardinella maderensis
Catches of S. maderensis
showed a decrease at the level of the subregion, from 148 591 tonnes in 2010 to 124 735 tonnes in 2011. Catches in Mauritania decreased from 42 495 tonnes in 2010 to 26 247 tonnes in 2011. This decrease was found mainly in the landing by the artisanal fleet. Also in Senegal the catch of this species decreased, from 100 755 tonnes in 2010 to 90 355 tonnes in 2011. Fishing effort
Available data on effort by country and fleet are given in Table 3.2.2 and Figure 3.2.2 .
In Mauritania, effort by the Dutch-type trawlers increased by 106 percent compared to 2010. This continued increase in effort was again related to the return of large vessels that had fished in the Pacific in previous years. There was also a considerable increase of Russian-type effort. Updated figures available from IMROP show that this increase started already in 2010.
In Senegal the effort of the artisanal fishery targeting Sardinella
spp. in 2011 decreased by 10 percent compared to 2010. No split was available of artisanal effort directed at sardinella in Mauritania (canoes operating from Saint-Louis) and effort in Senegalese waters. The effort in the Senegalese artisanal fleet, expressed in number of canoe trips, has remained rather constant since the beginning of the series (Figure 3.2.2). This series, however, does not take into account the increase in average size of the canoes. In reality, therefore, fishing effort in the artisanal fleet has probably increased.. Recent developments Mauritania
Fishing effort by the Dutch-type trawlers further increased in 2011, due to the return of vessels that had been working previously in the southern Pacific. The declining catches in the Pacific have stimulated a transfer of effort from this region to Mauritania. This applies not only to vessels that earlier worked in Mauritania (such as the Dutch-type trawlers), but also to trawlers that never worked in Mauritania before. These include the factory vessel LAFAYETTE with a processing capacity of 1 500 tonnes/day that receives fish from its own fleet of small purse seiners. In addition, there were vessels from China and Vanuatu that moved from the Pacific to Mauritania. All these new arrivals caused a significant increase in fishing effort already in 2010, and the Russian-type effort remained at this high level in 2011.
The recent expansion of the fish meal industry in Nouadhibou was halted in 2011. Catches of sardinella landed by the artisanal fleet for this purpose declined by 47 percent. This decline in landings was due partly to new regulations concerning the minimum number of Mauritanian fishermen on board the canoes (formerly the crews existed exclusively of Senegalese fishermen). However, the decline in catches was also due to a reduced abundance of the sardinella in the coastal zone. Senegal
There are still a large number of foreign fish traders in Saint-Louis and along the "Petite côte" (Mbour and Joal) that are buying sardinella. The strong demand for sardinella has further increased by the construction of fish meal factories.
The creation of so-called local “co management commissions” with the support of local entrepreneurs of the artisanal fishery and representatives of the government is increasing at certain landing sites such as Kayar and along the "Petite Côte" (Ngaparou and Pointe Sarène).
In Senegal, landings of juvenile fish of pelagic are forbidden at the various landing sites, and the offenders are punished by penalties and sanctions.
The number of canoes licensed to fish in the Mauritanian zone was decreased from 300 in 2011 to 275 in 2011, and the duration of the licences was reduced from 12 to 3 months. The restrictions concerning catches per trip and number of trips, the ban on certain fishing gears like the driftnet, and the obligation to land 15 percent of the catches in Mauritania are still in force.
The industrial fleet is composed of small local purse seiners that are called "sardiniers dakarois". The size of this fleet has not changed since 2010 (three units in operation). A closed period was introduced during the month of October for this industrial fleet.
In 2011, Senegal issued 22 fishing licences to Russian trawlers fishing for coastal small pelagics.
Starting from 2008, there has been no complete coverage of the entire distribution area of sardinella by acoustic surveys. Therefore, the working group in 2011 decided to replace the acoustic abundance index by the CPUE of the Dutch type fleet in Mauritania. This year, the same procedure has been followed. The CPUE for the Dutch type fleet in 2011, based on data supplied by the Dutch ship owners was used for the assessment. Although these data for 2011 cover only a fraction of the Dutch type fleet, this "traditional" index was more comparable to the values used in previous years than the new index calculated on the basis of IMROP data (Section 3.3.1).Input parameters for the dynamic production model
The dynamic production model has been run both for S. aurita
and for the two sardinella species combined.
The initial parameter values are presented in Table 3.6.1.
As in last year's assessment, a positive environmental effect was included in years in which a strong year-class of S. aurita
was assumed to have been born. From the length compositions in Mauritania it has been noticed that strong year classes were born in 2005 and 2007 (these year classes resulted in large catches of 3-year old in 2008 and 2010). Hence, a positive environmental effect has been applied to both years (+1.0 for 2005 and +0.5 for 2007 in the case of S. aurita
, and +1.0 and +0.3 in the case of Sardinella
In the absence of adequate data for an age-based analysis, the group decided to use the same production model that was used during previous meetings. This is the Schaefer dynamic production model, implemented on an Excel spreadsheet (Appendix II).
Overall Assessment Results
The model has been run both for S. aurita
, and for the two species combined. It was not considered realistic to run the model for S. maderensis
only, as the CPUE for the Dutch type fleet in Mauritania refers to a fishery that is directed primarily to S. aurita
In both cases, the model does not provide a good fit of the predicted abundance against the observed abundance.Discussion
The very low stock sizes estimated by the model may be partly due to a bias in the abundance index used, particularly the redirection of the Dutch fishing effort towards sardine during the first quarter of the year. However, despite the inaccuracies in the CPUE and their possible effects on the results of the Biodyn model, there is no doubt that the stock of adult sardinella has further declined in 2011. This was due both to the absence of new recruitment in that year, and to the sharp increase in fishing effort. This increase in fishing effort has resulted in record catches in 2011, but at the same time in a further depletion of the stock.
As mentioned in last year's report, fishing effort is now at such a high level that even strong year-classes are depleted within one or two years. The fishery has been able to sustain the high catch levels in recent years only because of the strong year classes entering into the fishery in 2005 and 2007.
The development of the stock in future years will depend both on the incoming recruitment and on the regulation of fishing effort. The high catches of juvenile S. aurita
north of Cap Blanc in 2011 could be an indication of improved recruitment. However, even if recruitment would go up in 2012, this will only temporarily improve the stock situation, as long as the current high fishing effort continues. Therefore, in order to rebuild the stock and to stabilize catches of adult sardinella, fishing effort has to be considerably reduced.
The very low stock sizes estimated by the Biodyn model for 2011 were not suitable as a starting point for stock projections for the next five years. The development of the stock will depend Overexploited
not only on the stock size in 2011 and the intrinsic growth rate (r
), but much more on the strength of the incoming year-classes. This recruitment in the next few years is unknown, and therefore the development of the stock in the next years is unpredictable.
Scientific AdviceFuture research Follow up on last year’s recommendations:
- Coverage of the total subregion during the acoustic survey in 2011 was not obtained.
- No progress was made in Mauritania and Morocco in cooperating with the Senegalese project on age reading.
- No subgroup was established to consider the possibility to establish a series of recruitment indices for S. aurita, using length data from commercial catches and the acoustic data.
- Discrepancies in Mauritanian catch statistics for EU fleet were resolved.
- Sampling of artisanal catches in Mauritania was improved, but the results were not available to the meeting.
- No sampling data for artisanal catches in Senegal at different landing sites were available at the meeting.
For this year, the Working Group formulates the following recommendations:
- Effort statistics for the industrial fleet in Mauritania were improved.
- Biological sampling of landings in Las Palmas and analysis of data was continued.
for Management consideration
- Coverage of the total subregion by national acoustic surveys in 2012.
- Splitting of data on landings, fishing effort and length composition by main landing sites in Senegal.
- Correction of artisanal effort data taking into account the increased fishing power of the canoes.
Current catches of sardinella are not sustainable. Catches have to be reduced in order to avoid a future depletion of the stock. The Working Group recommends a reduction in fishing effort in 2012, and reinforces the recommendations expressed in the Working Group of 2010 and 2011.
The Working Group could not make a catch recommendation as at present it is unable to predict future recruitment.