Report of the FAO Working Group on the Assessment of Small Pelagic Fish off Northwest Africa
Subtitle: Nouakchott, Mauritania, 21-30 April 2009
Publisher: Food & Agriculture Organization of the United Nations
Published: 2011
Language: eng
Number of pages: 252
ISBN-13: 9789250068824
Description: The ninth meeting of the FAO Working Group on the Assessment of Small Pelagic Fish off Northwest Africa was held in Nouakchott, Mauritania, from 21 to 30 April 2009. The Group assessed the state of the small pelagic resources in Northwest Africa and made projections of the development of the stocks and of future effort and catch levels. The advice for the stocks are given in relation to the agreed reference points F0.1, FMSY, B0.1 and BMSY and on the basis of the projections for the next five years. The structure of the report is the same as that of the previous Working Group reports (FAO, 2002-2008). A separate section is devoted to each of the main groups of species (sardine, sardinella, horse mackerel, chub mackerel, bonga and anchovy). For each of these, standardized information is given on stock identity, fisheries, abundance indices, sampling intensity, biological data, assessment, projections, management recommendations and future research.

The Working Group used dynamic production models for all stocks. An index of environmental quality has been introduced in the production models since 2005. For most of the stocks, the time series from the acoustic surveys with the R/V DR. FRIDTJOF NANSEN and national research vessels are used as the index of abundance in the assessments and future assessments would therefore depend on the continuation of the time series by the local research vessels. The Norwegian research vessel, DR. FRIDTJOF NANSEN surveyed the subregion from 1995 to 2006, carrying out acoustic surveys during the months October-December each year. In addition, from 2001 to 2003, the vessel carried out acoustic surveys covering the same area from May to July. From 2004 to 2006, intercalibrations and parallel surveys were carried out between R/V DR.

FRIDTJOF NANSEN and the national research vessels AL AMIR, AL AWAM and ITAF DEME and in 2007 and 2008 these national research vessels carried out a coordinated regional survey during the months of October-December. It should be noted that during the 2008 survey, the Gambia was not covered. The Nansen series is continued with data from the national research vessels converted to a "Nansen Value". With the exception of sardine (Sardina pilchardus) in zone C, the other small pelagic fish stocks in the region were considered to be either fully exploited or overexploited. Sardine in zone C did not show signs of overexploitation and the estimated biomass index from the regional survey (November-December) increased in 2007 as compared to 2006, followed by a decrease of 18 percent in 2008. Nevertheless, given the fluctuations observed in the abundance of this stock, care should be taken in its management.

The situation for the sardine stock in zones A+B seemed to have improved since 2006 and this stock was considered fully exploited. Cunene horse mackerel (Trachurus trecae) was found to be overexploited and the recruitment survey index suggested a poor recruitment for 2008 compared with 2007. In addition, a change of exploitation pattern occurred with higher catches of smaller fish in 2008. The state of the stock of Atlantic horse mackerel (Trachurus trachurus) seemed to have improved in 2008, which was probably due to a good recruitment in 2007. This stock was considered fully exploited. However, because the horse mackerel fishery in parts of the zone does not make a distinction between the two species, an overall reduction of effort on these species was recommended. The catches of round sardinella (Sardinella aurita) were high over the last three years, probably associated with a very good recruitment in 2005, but there was no evidence of another good year class since.

For this reason the Working Group continues to be concerned about this stock and still considers it as overexploited. Chub mackerel (Scomber japonicus), anchovy (Engraulis encrasicolus) and bonga (Ethmalosa fimbriata) were found to be fully exploited. For the latter two species, the Working Group noted the deficiency of the available catch and effort data. Without reliable commercial data it was not possible to conduct reliable assessments. With the exception of bonga, anchovy and flat sardinella, the Working Group succeeded in providing a model based assessment of all the main small pelagic fish stocks considered, using available estimates of total catch and abundance indices. However, the Working Group considers that the assessments could be greatly improved if more and better data were available. In 2007 and 2008, the national research vessels took over the responsibility of the November-December acoustic survey from the R/V DR. FRIDTJOF NANSEN.

Many of the assessments made by the Working Group depend on this time series and hence the Working Group reiterated last year's recommendation that a thorough analysis of the properties and reliability of this data series should be carried out according to agreed terms of reference. It also recommended continuing work on age reading of sardine and sardinella to improve the models of stock assessment.