Research activities carried out by IEO in the Canary Islands during intersession

Regarding the research activities carried out by Oceanographic Centre of the Canary Islands (IEO-CSIC) during intersession, several studies on different topics were presented. Firstly, reproductive traits for the four main species have been analysed including all the data obtained since the monitoring system was launched in 2013. Although with some variations, the spawning season matched with winter and beginning spring for S. colias, T. picturatus and S. pilchardus. However, spawning individuals of S. aurita are present all year round. Sizes at first maturity (SFM) were also estimated, with slightly smaller sizes obtained for S. colias and T. picturatus (around 19 cm of total length) compared with the reference values (20 cm and 23 cm, respectively) (Jurado-Ruzafa and Santamaría, 2013; Lorenzo and Pajuelo, 1996). It seems that SFM remains stable for S. pilchardus (15 cm) (Méndez-Villamil et al., 1997). In the case of S. aurita, size at first maturity has been estimated for the first time in the Canary Islands, and has been recently published (Jurado-Ruzafa et al., 2022). Secondly, a first attempt to describe total catches of the Canary artisanal purse-seine fleet based on scientific observation shows that discards are more relevant than what was supposed, reaching the 25 percent of the total catches. The situation is even more concerning if only S. colias is considered, with discards around 40 percent of the total catches, mainly impacting on juveniles’ fraction, which is usually used as bait by commercial vessels but that are not officially reported. Finally, very preliminary results were shown to the working group about the potential adaptive plasticity in Scomber colias from the Canary Islands, based on otolith shape analyses. These results were obtained from analysing 748 otoliths extracted from August 2016 to December 2017. A DIvisive ANAlysis (DIANA) Clustering method using the fourth wavelet obtained from otolith contours resulted in the detection of five different morphotypes (or otolith phenotypes), with two of them representing 85 percent of the samples analysed, and whose individuals were slightly larger than for the other morphotypes. Further questions should be explored, addressing possible intraspecific variation in the growth rate among phenotypes; phenotypes proportions change in relation to seasonal variations; existence of different ecological strategies related to each phenotype and the presence of these otolith phenotypes in other geographical areas, as it has been described for T. picturatus (Tuset et al., 2019; Vasconcelos et al., 2021). References Jurado-Ruzafa, A. and M.T.G. Santamaría. 2013. Reproductive biology of the blue jack mackerel, Trachurus picturatus (Bowdich, 1825), off the Canary Islands. Journal of Applied Ichthyology, 29(3): 526–531. Jurado-Ruzafa, A., B. Sotillo de Olano, Z. Santana Arocha, B. G. Mañé, C. Estil-las, E. Hernández, S. Jiménez, G. González-Lorenzo and C. Perales-Raya. 2022. Reproductive traits of the round sardinella in the Canary Islands (Spain, NW Africa). Journal of the Marine Biological Association of the UK, (early view) 1-7. Lorenzo, J. M. and J.G. Pajuelo. 1996. Growth and reproductive biology of chub mackerel Scomber japonicus off the Canary Islands. South African Journal of Marine Science, 17(1): 275-280. Méndez-Villamil, M., J.M. Lorenzo, J.M. González and R. Soto. 1997. Periodo reproductor y madurez sexual de la sardina Sardina pilchardus (Walbaum, 1792) en aguas de Gran Canaria (Islas Canarias). Boletín del Instituto Español de Oceanografía, 13(1-2): 47-55. Tuset, V.M., A. Jurado-Ruzafa, J.L. Otero-Ferrer and M.T.G. Santamaría. 2019. Otolith phenotypic variability of the blue jack mackerel, Trachurus picturatus, from the Canary Islands (NE Atlantic): Implications in its population dynamic. Fisheries Research, 218: 48-58. Vasconcelos, J., A. Jurado-Ruzafa, J.L. Otero-Ferrer, A. Lombarte, R. Riera and V.M. Tuset. 2021. Thinking of Fish Population Discrimination: Population Average Phenotype vs. Population Phenotypes. Frontiers in Marine Science, 8(1489)

Age of spent Octopus vulgaris and stress mark analysis using beaks of wild individuals

Age estimation of the cephalopod Octopus vulgaris by using beaks has improved in recent years, but maximum age and longevity in the wild have not been confirmed due to the low availability of senescent wild octopuses. In this study, a beak analysis of lateral wall surfaces (LWS) from 20 spent specimens confirmed the one-year lifecycle of the species in Central East Atlantic waters. Stress marks (checks) were clearly located in the daily increment sequence of rostrum sagittal sections (RSS). The highest daily variations in sea surface temperature (ΔT) that occurred during the last months of their lifetimes coincided with the locations of the marks on the beak, enabling confirmation of O. vulgaris beaks as life recorders for the first time. It also supports the daily deposition of RSS beak increments in the wild. Individuals were grouped into two main zones, at 20ºN and 18ºN respectively. Both groups showed different thermal check patterns, in accordance with the oceanographic differences. Two other checks (not coinciding with high values of ΔT) were observed in RSS at averages of 15 and 28 days before death, respectively, which were interpreted as responding to senescent-related events.Instituto Espanol de Oceanografi

The Atlantic Chub Mackerel (Scomber colias) in the Canary Islands (Spain): Fishery and Biological data Update

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Second Workshop on Atlantic chub mackerel (Scomber colias) (WKCOLIAS2)

The Atlantic chub mackerel Scomber colias has become an increasingly important commercial species in the European Atlantic waters in the last 10–15 years, probably through an expansion process from NW African waters and due to market needs. However, at present there are no assessment or advice requirements. In the WK framework, available information of the species in the West Atlantic waters has been compiled in order to evaluate possible geographical differences and trends, and the feasibility to describe its population structure. Though the Atlantic chub mackerel is not routinely included among the target species in the acoustic surveys performed in the Atlantic Iberian waters and the Mediterranean Sea, a synoptic overview of the species is possible over all its West Atlantic distribution. Moreover, the data available have indicated latitudinal trends, mainly in the landings’ length composition, L50 and the spawning periods. Nevertheless, even if some degree of connectivity likely exists and migrations are occurring between adjacent areas, some subunits could be considered for management purposes. From the assessment models’ trials carried out, the results or reference points obtained for the European fisheries cannot be retained at present. Therefore, continuing collating information from fisheries and biological sampling of the species, obtaining reliable biomass estimations from scientific surveys and identifying management units seem the main priorities to address in future research work and in case of assessment requirements