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Report of the Workshop for maturity staging chairs (WKMATCH), 11–15 June 2012, Split, Croatia

AuthorsSaborido-Rey, Fran ; Basilone, Gualtiero; Belcari, P.; Ferreri, Rosalia; Kec, Vanja; Kjesbu, Olav S.; Korta, María; Nash, Richard D. M.; Villamor, Begoña; Zorica, Barbara
Issue Date2014
PublisherInternational Council for the Exploration of the Sea
CitationICES CM 2012/ACOM 58: 1-29 (2014)
AbstractThe recorded maturity stage at the time of observation is an important biological parameter to be used in the calculation of maturity ogives (and therefore of Spawning Stock Biomass), for the definition of the spawning season of a species, for the moni-toring of long-term changes in the spawning cycle, and for many other research needs regarding the biology of species. Thus, maturity data are fundamental part of the stock assessment process and hence a vast effort is put on validating the macro-scopic inspection of gonads. In the last decade a series of workshops addressed the maturity staging of different species with the objective of developing common ma-turity scales, decreasing discrepancies between laboratories and validating maturity staging through microscopic evaluation. A total of 11 of those workshops on species-specific maturity staging were revised here. These workshops have analysed 20 teleosts, elasmobranchs as a whole subclass, three orders of cephalopods and four crustacean species. The WKMAT 2007, and later WKMSCWHS 2007, proposed a six point maturity scale for both males and fe-males that have been used as a reference in the different maturity workshops to de-velop and adopt a common scale between laboratories for each species. A notable effort has been made by all workshop participants to standardize the existing maturi-ty scales and accommodate the standard scale proposed. All workshops acknowl-edged the biological differences between the reference scale stages. All workshops proposed new scales that although were generally consistent with WKMAT scale, showed several differences. As a result, the four stage scale proposed in WKMAT has generally not adopted, partially because such scale does not allow reflecting specific particularities, useful for a number of species.
To overcome this, we propose the use a single scale of 4+2 stages or divisions which is believed to be universal, that is, it can be used for the majority of species, although viviparous and hermaphrodites may need some adaptation. This 6 stage codes and names should be used for all species and both sexes without exception; species-specific particularities should be reflected creating subdivisions and never modifying the 6 main stages. Using this proposed coding system, particularities of species and stocks can be addressed by each workshop (subdivisions), without losing consistency and traceability (divisions). In this way the code number of the divisions or main stages has the same biological meaning across species and laboratories. Some poten-tial subdivisions are proposed as well, for its facultative use in some batch spawners an in viviparous species. The merging of different stages should be avoided and in-stead a combined code should be used. In this manner the consistency of stages defi-nition and codes is maintained across species. The definition of each stage needs to be linked to biological phases and incorporate into its description species-specific aspects relevant for an easy identification of each stage. The use of the terminology for maturity stages considers a general scheme of the reproduction that can be applied to all male and female elasmobranchs and tele-ost fishes, including hermaphrodites and livebearers. A full glossary of terminology was compiled. Training (of the observers) is the major issue for maturity staging, and it should be strengthen within the umbrella of ICES.
When staging maturity macroscopically timing of the sampling is critical to obtain reliable results. To define this period it is important to know the timing of the repro-ductive cycle, as this is species specific. If maturity staging outside the optimal peri-ods is required, this should be based on histological information. However, we suggest that whole mounts preparations are useful to validate macroscopic staging of ovaries being particularly useful to separate between early developing and develop-ing specimens, immature and regressing/regenerating specimens, or even specimens that have just completed a spawning season from those have not yet entered sexual maturity. Nevertheless, it is recommended that the whole-mounts method is careful-ly calibrated before taken into practical use. The maturity Workshops should discuss the new and general scale in their respective WKs by e-mail to assess the correspondence with the agreed scale, and evaluate the uncertainties and the problems this new general scale may cause. At the same time, ICES should ensure an appropriate attendance and a required level of basic knowledge, both on maturity studies and on the species targeted by the Workshop. Beyond of experts in the matter, the participants should be trained people, this can be achieved by training courses in ICES. We have revised and updated the Guidelines for Workshops on Maturity Staging, and provided general recommendations for future workshops.
We reviewed a total of 148 stocks of 53 species from 8 ecoregions from which ICES provides some type of advice. In 88 stocks (59%) maturity data are not used or are used improperly. This includes the use of time invariant maturity ogives when annu-al ogives can be available. In 39 stocks (26%) the assessment uses a proper maturity ogive, but over a limited time period. Finally in only 21 stocks 14% of the total ad-vised stocks the maturity ogive has been estimated on regular basis and in these cases they are used properly in the assessment. Therefore, lack of data and/or poor quality is the main causes of maturity not being used. However, there is a general lack of information in the reports on how the maturity data was collected, ogive estimated, quality control and other relevant information. There is a need to determine what maturity data are required for assessment purposes, including how phenomena such as skipping spawning should be included in assessments. In spite of the effort on collecting maturity data, almost in 100% of the cases sex-specific ogives are combined without analysing the impact of this. Expert groups should provide comprehensive reports on how the maturity data is used, and more specifically, at least: the method used to estimate maturity, in which sex and how a sex-specific maturity ogive is used in the assessment, source of data (survey, commercial sampling), the time of the year when the sampling was conduct-ed, and years of proper estimation. The impact on the assessment of combining sex-specific maturity ogives should be analysed.
Description59 páginas, 8 anexos
Publisher version (URL)http://ices.dk/sites/pub/Publication%20Reports/Expert%20Group%20Report/acom/2012/WKMATCH/WKMATCH%20Final%20Report%202012.pdf
Appears in Collections:(IIM) Informes y documentos de trabajo
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