Preliminary Age-length key by reading otoliths of antarctic toothfish (Dissostichus mawsoni)We present preliminary results on age and growth of Dissostichus mawsoni for the
second season (2013/14) of the Spanish research fishing in the 58.4.1 Division
obtained for growth rings on otolith readings. It is included the age-length key and
growth parameters estimates by sex. Growth parameters obtained using length-age
pair values are: L∞: 175.7, k: 0.1078 and t0: 1.528 for females; L∞: 150.3, k: 0.1491
and t0: 1.809 for males; and L∞: 169.8, k: 0.1087 and t0: 1.168 all combined. These
results are very similar to those reported previously for the first season (2012/13)
although they differ slightly with the values used in the Ross sea assessment for
males

Barreiro-Jueguen, S. (Santiago)

López-Abellán, L.J. (Luis José)

Santamaría, M.T.G. (María Teresa García)

Sarralde-Vizuete, R. (Roberto)

English

Repositorio Institucional Digital del IEO

WG-FSAThis paper is presented for consideration by CCAMLR and may contain unpublished data, analyses, and/or conclusions subject to change. Data in this paper shall not be cited or used for purposes other than the work of the CAMLR Commission, Scientific Committee or their subsidiary bodies without the permission of the originators and/or owners of the data.Commission for the Conservation of Antarctic Marine Living ResourcesCommission pour la conservation de la faune et la flore marines de l’AntarctiqueКомиссия по cохранению морских живых pесурсов АнтарктикиComisión para la Conservación de los Recursos Vivos Marinos AntárticosOriginal: EnglishL.J. López-Abellán, M.T.G. Santamaría, R. Sarralde and S. BarreiroWG-FSA-16/58Update of ongoing work on age and growth of Antarctic toothfish(Dissostichus mawsoni) (2013-14 season) from Division 58.4.1 bySpain18 September 20161  Update of ongoing work on age and growth of Antarctic toothfish (Dissostichus mawsoni) (2013-14 season) from Division 58.4.1 by Spain    L.J. López-Abellán, M.T.G. Santamaría, R. Sarralde, S. Barreiro Centro Oceanográfico de Canarias, Instituto Español de Oceanografía    Abstract  We present preliminary results on age and growth of Dissostichus mawsoni for the second season (2013/14) of the Spanish research fishing in the 58.4.1 Division obtained for growth rings on otolith readings. It is included the age-length key and growth parameters estimates by sex. Growth parameters obtained using length-age pair values are: L∞: 175.7, k: 0.1078 and t0: 1.528 for females; L∞: 150.3, k: 0.1491 and t0: 1.809 for males; and L∞: 169.8, k: 0.1087 and t0: 1.168 all combined. These results are very similar to those reported previously for the first season (2012/13) although they differ slightly with the values used in the Ross sea assessment for males.     Introduction    From 2012-13 Spain is conducting fishing research in the 58.4.1 Division in order to get data and biological samples which enable an assessment of Antarctic toothfish in this area at the end of the whole experience. Up to now three surveys have been completed and the WG-SAM-15 requested to Spain to provide additional information on the otolith readings progress to WG-FSA-16.    The Spanish Institute of Oceanography (IEO) is working on the ageing and growth estimates of Antarctic toothfish since 2015. Thus, this document is a progress of the work presented last year (WG-FSA-15/06), following the same methodology. Samples studied were obtained in the course of research experiments conducted by the Spanish flagged vessel Tronio in Division 58.4.1 in the fishing season 2013-14. Otoliths from 495 specimens were used in this second approach to ageing individuals of this species in order to construct the age structure of fished population and to estimate the growth parameters.   In this process, a set of 40 otoliths used as a reference were provided by the CCAMLR Secretary to exchange and fix the ageing criteria among readers. Also  coordination between readers from the Republic of Korea and Spain has been made using pics of the cut otoliths (both raw and with the interpreted age marked).   For the otolith preparations and ageing we followed the methodology described on the Manual for age determination of Antarctic toothfish (Sutton et al., 2012) as “bake and embed” technique. 2  Otolith interpretation and age determination  Table 1 includes the numbers of D. mawsoni otolith samples collected by Spain, prepared (mounting and sectioning) and aged by fishing season.   Table 1. Numbers of otolith samples of D. mawsoni obtained by Spain in the 58.4.1 Division by season.  Season Collected Prepared Aged 2012 -   2013 696 696 514 2014 1242 600 495 2015 -   2016 562 363 - Total 2500 1659 1009   In this second phase on the ageing of D. mawsoni from Division 58.4.1, the protocol adopted consisted of:   Readings are still made by two pairs of readers. The first one were two experienced scientist that taught about the interpretation pattern to the other pair.   The work is in progress. And only results from one of the two pair of readers are presented here. Final agreement on the results with two other readers is waiting for comparison.     At this stage, considering the protocol followed by the readers where the age interpretation has been made by consensus between pairs, we wait for the second pair of readers to finish the otoliths set in order to compare all readings.    Age-length key and mean length analysis   Table 2 shows the preliminary age-length key estimated for all individuals, where the length ranged from 45 cm to 200 cm total length and ages ranged from 5+ to 36+. Few individuals with more than 31 years were found in the whole sample analyzed.             3  Table 2. Age-length key for D. mawsoni from Division 58.4.1 in the fishing season 2013-14.                                                                                                     Length interval (cm)/  Age class (years)5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 3645 15055 2 160 2 2 1 165 1 5 3 8 1 170 2 4 5 4 175 2 6 1 1 280 1 2 5 1 185 2 1 2 1 290 1 2 4 1 195 3 5 3 2 4 2 2100 2 4 4 5 2 1 1 2105 2 2 4 4 4 2 2 1 1 1110 1 1 2 3 3 6 3 2 1 1115 2 2 2 4 2 5 1120 1 4 3 1 1 2 1 4 2 1 1 1 2 1125 5 2 3 1 2 2 1 1 1 2 1 1 3 1 2130 2 3 5 3 3 1 1 1 2 2 2 1 1135 4 2 1 2 4 3 1 1 2 1 2 1 1140 1 1 3 3 4 1 4 3 1 2 2 2 1145 2 1 1 6 1 3 2 2 1 4 3 1 1 1150 1 3 5 3 3 2 5 2 2 2 1 1 1155 1 2 3 1 1 3 2 3 2 1 5 1 2160 1 2 1 2 1 1 3 4 1 2 3 1 2 1 2165 1 1 2 2 1 3 1 1 2 1 3 1 1 1 1 1 1170 3 1 4 2 1 2 2 2 1175 1 1 1 3 1180 1 1 2 1 1185 1 1190 1195 1 1n 9 14 26 31 20 34 23 27 19 28 15 17 24 25 17 21 27 12 21 26 19 10 9 6 3 5 6 1 0 0 1 1M ean length(cm) 68.06 68.93 82.88 84.92 98.75 105.44 109.24 113.06 117.24 125.00 135.83 143.09 150.21 147.30 151.32 147.50 150.09 152.50 152.02 156.54 155.66 156.00 160.28 155.83 155.83 165.50 159.17 137.50 167.50 167.50SD 18.45 5.69 13.56 15.86 13.66 16.43 16.83 12.51 18.52 18.08 15.20 15.09 16.87 15.64 16.25 13.96 17.99 18.09 20.18 17.26 20.22 17.17 5.65 13.29 12.58 10.95 17.224  Growth parameters  A von Bertalanffy growth function based on a least-square fitting approach from length-age pair values had been estimated. Growth parameters by sex and combined are presented in Table 3.   Table 3. Parameters of von Bertalanffy growth fitting by sex and all sex combined, for D.  mawsoni from Division 58.4.1 and standard error estimations for 2013/14 season and number total of otoliths read.  n Sex  t0 (y)  k (y–1 )  L∞ (cm)  208 Male  1.809 0.1491 150.3 287 Female 1.528 0.1078 175.7 495 Combined 1.168 0.1087 169.8           Standard error Male  0.548 0.01781 3.562 Female 0.596 0.01237 4.626 Combined 0.4674 0.009768 3.593   Figure 1 shows pair values and growth curve fitted for males, females and both sex combined for the 2013/14 season as well as a comparative with the previously obtained from the 2012/13 season. Results of all sex combined are very similar although the fitted curve by sex differs slightly being the 2012/13 estimated values of L∞ lower for females and bigger for males than the obtained with the 2013/14 season set.   Figure 1.- Values of length-age used to estimate growth parameters and growth curves fitted for males, females and all combined by season.    5  Comparing visually our results with the age-length curve used in the Ross sea assessment (CCAMLR, 2015) in Figure 2, our estimates of L∞ are lower in all cases.     Figure 2.- Values of length-age used to estimate growth parameters and growth curves fitted for males and females by season in division 58.4.1 and the Ross sea.   Work in progress  The annually age estimation from the Antarctic toothfish samples will continue and progress reports will be reported to WG-FSA. The finalization of the ongoing otolith readings of the 2013/14 season for the two remaining readers will enable to compare between reader pairs and to obtain the final result. It is expected to finish with the 2015/16 set from the last season research survey onboard the F/VTronio before the WG-SAM-2017 meeting.   A set of 40 otoliths used as a reference has been provided by the CCAMLR Secretary to coordinate the ageing among readers. Although this could be a useful tool to compare between members this set is not easy to interpret due to the confusing numeration of every otolith’s cut as well as the unclear images but also due to the inherent difficulties of the otoliths of toothfish itself, that provoke that discrepancies cannot be solved.   Coordination between readers of Republic of Korea and Spain has been made using pics of the cut otoliths (both raw and with the interpreted age marked) provided by the Korean colleagues. Some important discrepancies have been found and will be discuss between both members, especially concerning the 5-6 first rings identification and placement. We consider that the Korean criteria allocate in general the readings almost equidistant between rings along three different zones of the otolith. Even when is not always observed, the criteria of the allocation of the first (La Mesa, 2007) and subsequent rings should be considered.  6  References  La Mesa, M. (2007). The utility of otolith microstructure in determining the timing and position of the first annulus in juvenile Antarctic toothfish (Dissostichus mawsoni) from the South Shetland Islands. Polar Biol. 30: 1219-1226.  López-Abellán, L.J, M.T.G Santamaría, R. Sarralde and S. Barreiro (2015). Contribution to knowledge on age and growth of Antarctic toothfish (Dissostichus mawsoni) from Division 58.4.1. WG-FSA-15/06  Sutton, C.P., P.L. Horn. and S.J. Parker (2012). Manual for age determination of Antarctic toothfish, Dissostichus mawsoni V2. Document WG-FSA-12/43 Rev. 1. CCAMLR, Hobart: 30 pp.   CCAMLR fisheries report 2015: Fisheries report for exploratory fisheries in  Subarea 88.1. CCAMLR, 2015.  

Update of ongoing work on age and growth of Antarctic toothfish (Dissostichus mawsoni) (2013-14 season) from Division 58.4.1 by Spain

Abstract

Similar works

Full text

Available Versions

Repositorio Institucional Digital del IEO

Digital.CSIC