Costas, G. (Gersom)

dos santos Schmidt, T.

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dos Santos Schmidt, T.

Costas, Gersom

Digital.CSIC

Long term changes in length distribution and age structure of mackerel sampled during the triennial mackerel egg surveys

Repositorio Institucional Digital del IEO

Long term changes in length distribution and age structure of mackerel sampled during the triennial mackerel egg surveysTHASSYA C. DOS SANTOS SCHMIDTGERSOM COSTAS2001 2004Western and Southern mackerel componentsYears of sampling: 1987 – 2019  (triennial survey)- Data presented: 2001 - 2019Period: January to JulyArea: Eastern North Atlantic from Gulf of Cadiz to Background color: coverage area Shaded rectangles: 75% of egg productionthe Faroe Islands and Iceland along the continental shelf and the North SeaParameters: length, weight, maturity stage (Walsh scale), age2010 20132007Background color: coverage area Shaded rectangles: 75% of egg production20192016Background color: coverage area Shaded rectangles: 75% of egg productionYear Jan Feb Mar Apr May Jun Jul Total2001 0 0 0 0 162 646 0 8082004 0 101 621 726 350 656 182 26362007 0 446 685 1636 449 466 0 3682Biological data: Western and Southern mackerel components2010 181 1427 551 1641 971 594 409 57742013 0 579 1362 1083 613 474 0 41112016 0 495 441 1913 795 419 28 40912019 26 164 802 1161 618 415 137 3323Year Jan Feb Mar Apr May Jun Jul Total %2001 0 0 0 0 17 30 0 47 5.82004 0 0 0 0 49 29 0 78 3.0Biological data: Western and Southern mackerel componentsAge data availableBias2007 0 0 0 100 160 255 0 515 14.02010 0 0 50 28 316 132 0 526 9.12013 0 44 237 303 317 343 0 1244 30.32016 0 297 145 675 703 222 28 2070 50.62019 0 100 432 748 617 212 119 2228 67.0Length distribution: Western and Southern mackerel componentsTL = 31.6 TL = 30.8TL = 33.8TL = 31.0TL = 32.8TL = 34.7Interannual variation in length distribution and mean length TL = 35.5Length distribution per month in 2013- Selected just fish at stages 4 to 6 (Walsh maturity scale)- Mean length variation among monthsTL = 31.9TL = 35.3TL = 35.2TL = 33.7Length distribution: Western and Southern mackerel componentsTL = 34.3Age structure: Western and Southern mackerel componentsThe percentage of younger fish has decreased, and older fish, increased over the years~ 75% of mackerel caught from February to April are up to 7 years old, from May onwards the frequency has decreased to 50% (mainly in the latest years of the time series)  Spawning area divided into 3 areas1. Bay of Biscay (BoB; > 48°N)2. Ireland Sea (IRL Sea; > 48° and < 55° N)3. Scotland Sea (SCO Sea; > 55°N)Age distribution by areaAge structure: Western and Southern mackerel componentsBoB more older fish being collected over the years, same for Ireland SeaNorth Sea mackerel componentYear May June2002 0 50Year May June2002 0 502005 0 56Period: May or June2005 0 192008 0 362011 16 432008 0 2642011 101 1082015 0 2002017 0 400Data just from the NetherlandsTL = 33.4 TL = 32.9 TL = 30.3Length distribution and age structure: North Sea mackerel componentTL = 36.3TL = 33.2 TL = 34.4Final remarksCoverage area and number of fish increased over the yearsMackerel mean length varies over the years, and among months within a year.Decrease of the number of younger fish by month over the yearsIMPORTANT:Review the data base: will include some new data information (e.g. Gear data from Scotland, Norway data fromNorth Sea survey (2002 – 2011), updated data from IEO)- Data missing - e.g. sampling position, age dataThe data need to be carefully interpreted since different gears have been used for each participatingcountry/instituteResearch collaboration “Mackerel year class spatiotemporal dynamic” 22 scientists, from 12 institutes and universities in 11 countries, working with 10 time series on mackerel distribution, from 1980s onward, to describe distribution of different year classes for all seasons (feeding-wintering-spawning) from age 0 until it fades out at old age. fOctober 2020 meeting, split into 3 sub-groups:• Spawning Dynamic and Overwintering – Chair Aril Slotte,• Juvenile Dynamic – Chair Teunis Jansen,• Summer Feeding Dynamic – Chair Anna Olafsdottir. fSub-groups aim to present preliminary results to whole research collaboration in middle of December.From Berge et al., 2015Thank you for your attention!Questions?

http://www.repositorio.ieo.es/e-ieo/bitstream/10508/12470/1/Long_term_changes_LD_mackerel.pdf

Long term changes in length distribution and age structure of mackerel sampled during the triennial mackerel egg surveys

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