Non é doado contar os peixes do mar!

En prens

Validation of Cod maturity ogive in NAFO 3M. Effect of the reproductive ccycle moment on ogive estimation.

The Flemish Cap (FC) survey is the source of the Atlantic cod maturity data for SSB estimation. FC survey takes place when females are resting and discrimination between spawning active and inactive females is still possible testing the presence of postovulatory follicles, that remains several months after spawning. However, the best moment for discriminate active spawning females is during the spawning season. For 2012 and 2014, the maturity ogives calculated during the spawning season and when females are resting were compared. Assuming a seasonal growth for cod in 3M, the moment in which maturity is estimated, had no effect on the ogives estimation. Thus, it is recommended to continue employing in the 3M cod assessment the maturity ogives produced with the FC survey information

Atlantic mackerel daily spawning dynamics and implications for batch fecundity estimations

The present study contributes to a better understanding of the daily spawning dynamics of southern NEA mackerel (Scomber scombrus) with implications for the estimation of batch fecundity. It shows that there is a time window during the day, mainly in the afternoon, during which the advanced oocyte mode in imminent spawners separates from the remaining, smaller oocytes. This synchronicity in the separation of the spawning batch amongst imminent spawners corroborates evidence for the existence of daily spawning synchronicity in the population. This is particularly important for applications of the daily egg production method, DEPM, because such pattern facilitates both the ageing of eggs for the estimation of the daily egg production at sea and the ageing of postovulatory follicles for the estimation of spawning frequency. For NEA mackerel, batch fecundity could only be measured when a clear hiatus was established between the spawning batch and the smaller oocytes. Hydrated females that do not show such hiatus would not be valid for batch fecundity measurements suggesting that the “hydrated oocytes method” is not fully applicable for this stock. Knowing the time of day at which the batch is separated, will facilitate the sampling of valid females for the estimation of batch fecundity

3M cod possible technical measures: spatial / temporal closures

In 2019, the NAFO Commission requested the NAFO Scientific Council (SC) advice on possible technical measures to protect and improve the productivity of the 3M stock of Atlantic cod, Gadus morhua. The objective of this paper is to study possible protection measures related to the temporal and spatial closures of fishing activity. Analysis of historical maturity data indicates that the spawning time of 3M cod occurs during the first quarter of the year and that it is when 65% of the annual cod catch is made. The catch per unit of effort (CPUE) has generally higher values in this season than in the rest of the year and the mean length of caught cod in that season is generally above the length at maturity (L50). During this first quarter, trawl fishery activities are concentrated in a small area at the Southwest of the fishing ground, but, as our data comes from the fishery, we cannot conclude that this is the only spawning area as we have not information about cod activity in the rest of the area in that season. For all these reasons, it is concluded that a spawning closure of Flemish Cap cod fishery during the first quarter of the year may be a suitable measure to protect and improve the productivity of 3M cod stock

Calculation of mackerel adult parameters for the application of the DEPM in the western spawning area

The ICES Working Group on Mackerel and Horse Mackerel Egg Surveys (WGMEGS) coordinates the mackerel and horse mackerel egg survey in the Northeast Atlantic (NEA) and the mackerel egg survey in the North Sea. The working group plans and reports on these surveys, with recent attention focused on the execution of the surveys given the increasing demands related to covering the expanding survey area as well as balanced fecundity sampling. WGMEGS also addresses data quality assurance in macke-rel fecundity and total annual egg production estimation.Currently, there are 3 surveys in place which are carried out triennially and deliver standing stock bio-mass (SSB) indices: (1) the survey for the western and southern stock components of the NEA mackerel stock, as well as for the western horse mackerel stock, (2) the survey for the NEA mackerel North Sea stock component, and (3) the survey for the southern horse mackerel stock.For the North Sea component, the egg survey in 2017 revealed an estimated egg production of 201*1012, resulting in an SSB of 287*103 tons. This is a strong increase of more than 100*103 tons com-pared to 2015 (SSB = 170*103 tons). While peak spawning in the North Sea was covered, the coverage of the complete spawning season and area was insufficient to produce a reliable estimate of survey in-dices.In 2019, the application of an alternate transect survey design made it possible to survey the persis-tently expanding mackerel spawning area and season. Northern and northwestern spawning bounda-ries for mackerel during survey periods 5 (weeks 19 – 22) and 6 (weeks 23 – 26) were not fully deline-ated. Peak spawning was observed in period 4 (weeks 16 – 18). Subsequent analyses of survey results in conjunction with results from exploratory surveys in the inter-survey-years showed that the mackerel core spawning area was covered and a reliable estimate of mackerel annual egg production was deliv-ered. The estimate of total mackerel egg production was 1.64*1015, which is a decrease of 7.6% com-pared to that of 2016 (rev. 1.77*1015).Realized fecundity was estimated at 1147 per g female, revealing the SSB for the NEA mackerel stock in 2019 at 3.09 million tons indicating at 12 % decrease since the 2016 survey (SSB = 3.52 million tons). At only 1.78*1014 , total annual egg production (TAEP) in western horse mackerel was found to be lowest production reported in the time series since 1992. The spawning maximum was detected in the last pe-riod 7 (weeks 27 – 29). It can, thus, not be concluded that peak spawning and the entire temporal ex-tent of horse mackerel spawning had been sufficiently covered.To further improve the quality of the index time series, WGMEGS will continue to dedicate much of its work to survey design and quality assurance in mackerel egg production and fecundity estimation

Working Group on Mackerel and Horse Mackerel Egg Surveys (WGMEGS). 2021

WGMEG

IEO 2022 MEGS SURVEYS

Campañas de Ictioplancton para Evaluación de StocksCIE