Barnes, T.

Barreiro-Jueguen, S. (Santiago)

Farmer, B.

López-Abellán, L.J. (Luis José)

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

Sarralde-Vizuete, R. (Roberto)

English

López-Abellán, Luis José

Santamaría, María Teresa García

Sarralde-Vizuete, Roberto

Barreiro-Jueguen, Santiago

Digital.CSIC

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

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WG-FSAThis paper is presented for consideration by CCAMLR and may contain unpublished data, analyses, and/or conclusions subject to change.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 AntárticosWG-FSA-18/54 Rev. 103 octubre 2018Original: EspañolUpdate of ongoing work on age and growth of Antarctic toothfish(Dissostichus mawsoni) from Division 58.4.1 by Australia and SpainL.J. López-Abellán, M.T.G. Santamaría, R. Sarralde, S. Barreiro, B. Farmer and T.BarnesUpdate of ongoing work on age and growth of Antarctic toothfish (Dissostichus mawsoni) from Division 58.4.1 by Australia and Spain L.J. López-Abellán1, M.T.G. Santamaría1, R. Sarralde1, S. Barreiro1, B.  Farmer2 and T. Barnes2  1Centro Oceanográfico de Canarias, Instituto Español de Oceanografía. Santa Cruz de Tenerife, Spain.  2Australian Antarctic Division, Department of the Environment and Energy,203 Channel Highway, Kingston, Tasmania, Australia. 7050   1. INTRODUCTION Spain and Australia are conducting fishing research in the 58.4.1 Division from 2013 and 2017 respectively, in order to get data and biological samples which enable an assessment of Antarctic toothfish in this s o  c a l l e d  “ d a t a  p o o r ”  area at the end of the whole experience. From the five surveys completed the last two have been in coordination between the five proponents, namely Australia, Japan, Republic of Korea, France and Spain. Spain and Australia are working on the ageing and growth estimates of Antarctic toothfish from 2015 and 2017 respectively. Previous work h a s  b e e n  presented to the  FSA-WGs where a von Bertalanffy growth function based on a least-square fitting approach from length-age pair values had been estimated for every season.   An intersessional exchange of 40 “bake and embed” otolith samples, mounted by Spain, has been made in order to compare consistency in ages estimated by different readers. Each otolith were read by 6 readers (4 Spanish and 2 Australian). As a result of these comparative analysis further work about coordination between experienced and new readers is needed.    2. METHODS  An intersessional Exchange of 40 “bake and embed” (Sutton et al., 2012) otolith samples has been made between Spain and Australia. The objective is to compare consistency in age estimates for two CCAMLR members working in the same division. During the experience neither reader used fish length information or had prior knowledge of the age estimates obtained by the other reader throughout the process.    Spain has used a different readability index due to the integration of the readings into their National plan and the need of having a single agreed criterion. It is from 1= unreadable to 4=excellent.   1. Otolith unreadable 2. Otolith readable with difficulty; poor contrast between successive opaque and translucent zones 3. Otolith readable; less contrast between successive opaque and translucent zones than in 2, but alternating zones still apparent 4. Otolith very easy to read; excellent contrast between successive opaque and translucent zones   Readability index used for Australia is the recommended in the Manual for age determination of Antarctic toothfish, Dissostichus mawsoni (Sutton et al., 2012) going from 1 = excellent to 5 = unreadable.   1. Otolith very easy to read; excellent contrast between successive opaque and translucent zones 2.  Otolith easy to read; good contrast between successive opaque and translucent zones, but not as marked as in 1; potential error 1 opaque zone  3. Otolith readable; less contrast between successive opaque and translucent zones than in 2, but alternating zones still apparent; potential error 2 opaque zones 4. Otolith readable with difficulty; poor contrast between successive opaque and translucent zones; potential error 3 opaque zones 5. Otolith unreadable  The IEO (Spanish Institute of Oceanography)  is working in a way that two experienced readers started in 2015 working with a stereo microscope with a binocular head doing individual readings at the same time (López-Abellán et al, 2015). Two inexperienced readers have been working closely learning about the interpretation of the otolith banding patterns. Discrepancies were discussed and comparative tests between readers were routinely done, using the CCAMLR-NIWA R code AgeCompare library. The R scripts used in this analysis are available through the CCAMLR Secretariat.  After a discussions and adoption of interpretation pattern a final personal age assignment was made, keeping single readings when there were disagreements. During all the process a graphical analysis of the progress was performed.   For subsequent analysis it was decided to use the readings that obtained the best fitting. Results of these readings were presented later at the  FSA-WGs (López-Abellán et al 2015,2016 and 2017).   In 2018, 260 otoliths for the 2016/17 season have been read individually by 2 readers with less experience. An intercalibration between both readers have been made.   Otolith readings from the season 2016/17 has been made individually by two of the less experienced Spanish readers (Table 1) but calibration analysis are still pending to be finished.  Australian members have read two sets of otoliths from 2016 and 2017 seasons. Two readers with two different levels of expertise, one of them with few more years experience at reading toothfish otoliths at the AAD (Australian Antarctic Division).  Table 1: Reading experience of the readers and season that have been read for each.        SEASON Readers Reading experience 2013 2014 2016 2017 ESP1 High X X X   ESP2 High X X  X    ESP3 Low   X X X ESP4 Low   X X X AU1 High   X X AU2 Medium   X X   3. RESULTS More than 7000 otoliths of Antarctic toothfish have been extracted from 2013 of which ~2300 have been read (Table 2). Results from the 2017 season from Spain still need calibration so results are not showed.     Table 2.Number of Dissostichus mawsoni otolith pairs extracted by season for Australia and Spain. Numbers of otoliths aged are in parentheses. Season is abbreviated to the end year. Season AUS ESP 2013 0 696 (514) 2014 0 1262 (495) 2015 0 0 2016 344 (329) 562 (341) 2017 212 (200) 387 (260) 2018 2547 1273   Preliminary results on age-frequency by fishing blocks are showed in Figure 1. IN the research block the mode is ~15 years in the Spanish readings while ~13 years in the Australian.    Fig. 1. Age-frequency plots by member and Research Block. Reliability on readings of antarctic toothfish is low. Only 1.0% (ESP) or any from AUS of the otoliths sampled was considered easy to read, 12.2% (ESP) or 79.4% AUS readable,  59.2%  (ESP) or 19.8% (AUS) readable with difficulty and 27.6% (ESP) or 0.8% (AUS) unreadable (Figure 2).    Figure 2. Reliability on readings of antarctic toothfish by member and season.    3.1. Reference sets Age estimates  3.1.a. Comparison between AU1 and ESP1.  Age estimates for the the two more experienced readers of every member (AU1-ESP1) were similar, although a slightly lower age estimate for one of the readers, with 19% of the readings being different by more than 2 years and the mean differences being significantly different (P=0.116, Figure 3a,b). However, there was no difference in the age difference over the range of ages sampled (Figure 3c) and the overall CV was relativey low (~10%).     Figure 3: Comparison of estimated ages by AU1 and ESP1. (b, c) Solid lines indicate an expected relationship. Dashed lines show a linear regression for the dataset.  3.1.b. Comparison between AU1 and ESP2.  Interpretation of ages between ESP2 reader and AU1 is also similar. There are differences in estimates mainly for fish ages 13 to 20 (Figure 4b, c, P = 0.83, CV =10.9%).         Figure 4. Comparison of estimated ages by ESP2 and AU1  3.1.c. Comparison between AU1 and ESP3.  Although the mode of the differences between the less experienced readers ESP3 and AU1 was near zero, age estimates varied by more than five years and the mean difference was not statistically equal to zero (P=0, Figure 3a). Age estimates were closer for younger fish, but diverged by age 14 with the difference increasing for older fish (Figure 5b, c). Because of this difference and a high variance in agreement for individual ages, the overall CV was high across all age clases (15.27%) and the slope of the regression was not significantly different than 1.      Figure 5: Comparison of estimated ages by AU1 and ESP3 readers  3.1.d. Comparison between AU1 and AU2.  Age estimates for the 2 Australian readers were similar, although one of the readers tended to produce a slightly upper age estimate, with 31% of the readings being different by more than 2 years, and the mean differences being significantly different (P=0.103, Figure 6a,b). The overall CV was ~10%).  Figure 6: Comparison of estimated ages by AU1 and ESP3 readers 3.2. Age estimates for ESP3 and ESP4 of the 2017 Spanish collection.   Comparative analysis between the age estimates of the two Spanish less experienced readers for the 2017 season samples has been performed.   The otoliths sampled are 237. 36% of the readings being different by more than 2 years, and the mean differences being significantly different (P=0.011, Figure 7a,b). The overall CV was ~11%).   Figure 7: Comparison of estimated ages by ESP3 and ESP4 of the otoliths collected in 2017   4. DISCUSSION  The reading experience level of the age readers might have a significative effect according to the results of the comparative analysis performed. Results suggest an agreement in ages determined by experienced readers being lower with those with less experience although the “readability index” of the samples might have a strong influence in this variability  Age estimates by different age readers on the same samples allows differences in interpretation to be isolated and monitored within and between different ageing programmes. For programmes that use multiple age readers, monitoring age interpretation by individual readers through time and between age readers is an important and explicit quality assurance process (Campana 1995, 2001).  This study also highlights the importance and need for comparisons within and among ageing programmes as a routine procedure to provide confidence in the comparability of ages used for management (Parker et al, 2013). Spanish readings for the 2017 season were made for the less experienced readers. Data need to be calibrated and probably re-read again before results could be published.  (a)Santi  -  RobertoRelative frequency-15 -10 -5 0 5 10 15 2000.250.50.75% disagreement > 2 y ears = 36n = 237paired t-test p = 0.0110 5 10 15 20 25 30-505(b)SantiSanti  -  Roberto111324112451131421112251113621132411231111115131111212211111112111153331113112111133111212111152121212331411214121221112111111311112121110 5 10 15 20 25 30051015202530(c)SantiRobertoCV = 10.83%0 5 10 15 20 25 3005101520(d)SantiPrecison(first reader vs secon CVAustralia expects to have available a photographic reference set of  Antarctic toothfish for use between members very soon.    5. REFERENCES  Campana, S.E. (2001). Accuracy, precision, and quality control in age determination, including a review of the use and abuse of age validation methods. Journal of Fish Biology 59:197– 242.  Campana, S. E., Annand, M. C.; McMillan, J. I. (1995). Graphical and statistical methods for determining the consistency of age determinations. Transactions of the American Fisheries Society 124: 131–138. López-Abellán, L.J, M. 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  López-Abellán, L.J, M. Santamaría, R. Sarralde and S. Barreiro (2016). Update of ongoing work on age and growth of Antarctic toothfish (Dissostichus mawsoni) (2013-14 season) from Division 58.4.1 by Spain. WG-FSA-16/58.  López-Abellán, L.J, M. Santamaría, R. Sarralde and S. Barreiro (2017). Update of ongoing work on age and growth of Antarctic toothfish (Dissostichus mawsoni) (2013-14 season) from Division 58.4.1 by Spain. WG-FSA-17/66.  Parker, S.J.; Sutton, C.P.; Kuznetsova, E.N.; Petrov, A.F. (2013). Comparison of age readings by two otolith preparation techniques and readers. WG-FSA-14/53. 10 p.  Sutton, C.P., P.L. Horn., 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.   

http://www.repositorio.ieo.es/e-ieo/bitstream/10508/13674/1/24748.pdf

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

Abstract

Similar works

Full text

Available Versions

Digital.CSIC

Repositorio Institucional Digital del IEO