Models describing mackerel (Scomber scombrus) early life growth in the North and Northwest of the Iberian Peninsula in 2000

Abstract

SUMMARY: Mackerel (Scomber scombrus) in early life stages were captured in 2000 in the north and northwest of the Iberian Peninsula (ICES Divisions VIIIc and IXa North). Daily rings on their otolith sagittae were identified. Otoliths from 377 larvae and post-larvae caught in April and May 2000, ranging in length from 2.3 to 23.7 mm L S (Standard length) and ranging in age from 7 to 38 days after hatching were analysed. Additionally, 68 otoliths from juveniles and pre-recruits caught between July and October 2000 with a length range of 121-202 mm L S and aged between 65-186 days after hatching were analysed. Gompertz and Logistic growth models were fitted to the pooled length at age data of the larvae-postlarvae and juveniles-pre-recruits. As length at hatch is assumed in the literature to be 3.0 mm, the models were applied in two ways; not forced to pass through L 0 =3.0 mm and forced to pass through L 0 =3.0 mm. The unforced logistic growth curve appeared to be the most suitable for describing growth during the first year of life of mackerel (L ∞ = 191.6 mm; K= 0.070; t 0 = 66.7 d). . Los anillos diarios se han identificado en el otolito sagitta. Se ha analizado un total de 377 otolitos de larvas y post-larvas, capturadas en abril y mayo de 2000, con un rango de tallas entre 2.3 y 23.7 mm L S (Talla estándar) y con edades comprendidas entre 7 y 38 días después de la eclosión. Además se han analizado 68 otolitos de juveniles y pre-reclutas, capturados entre julio y octubre de 2000, con un rango de tallas entre 121 y 202 mm L S y edades comprendidas entre 65 y 186 días después de eclosionar. Se han ajustado los modelos de crecimiento Gompertz y logístico a los datos de las tallas por edad de las larvas, post-larvas, juveniles y pre-reclutas. Como se asume que la talla al eclosionar es de 3.0 mm, los modelos fueron aplicados de dos maneras; no forzados a pasar por L 0 =3.0 mm, y forzados a pasar por L 0 =3.0 mm. La curva de crecimiento logística no forzada a pasar por L 0 =3.0 mm parece ser la más adecuada para describir el crecimiento de la caballa durante su primer año de vida (L ∞ = 191.6 mm; K= 0.070; t 0 = 66.7 d).

Postflexion larvae and juvenile daily growth patterns of the Albor&aacute;n Sea sardine (<em>Sardina pilchardus</em> Walb.): influence of wind

“…This is the same pattern found previously in other daily growth studies on sardine juveniles (Álvarez and Butler, 1992;Álvarez and Morales-Nin, 1992;Alemany, 1993;Álvarez and Alemany, 1997;Álvarez, 2002), and even in other winter spawned pelagics off the Iberian peninsula, as Scomber scombrus (Cotano and Álvarez, 2003;Villamor et al, 2004). These patterns are probably influenced by endogenous factors, such as the decrease in potential growth with age; but they are also modulated by environmental factors, such as temperature and food abundance (Catalán et al, 2006;Ramírez et al, 2004).…”

Validation of daily increments in the otolith microstructure of Northeast Atlantic mackerel fish larvae

“…However, the utilisation of otolith microstructure analysis, in wild-caught specimens, is limited by the need of confirming the daily rhythm of ring deposition (Geffen, 1987). In this way, the formation of one growth ring per 24-h period has been assumed, but not validated, repeatedly within several field studies undertaken with Northeastern Atlantic mackerel larvae (Cotano and Alvarez, 2003;Villamor et al, 2004). Such findings have been based upon the results within the context of other validation studies, carried out with Northwest Atlantic mackerel (Migoya, 1989, unpublished).…”

“…The counting of daily increments and the measurement of increment widths, on Northeast Atlantic mackerel, Scomber scombrus (L.), otoliths has been utilised in several fisheries and ecological studies (Eltink, 1987;Dawson, 1991;Cotano and Alvarez, 2003;Villamor et al, 2001Villamor et al, , 2004. However, the utilisation of otolith microstructure analysis, in wild-caught specimens, is limited by the need of confirming the daily rhythm of ring deposition (Geffen, 1987).…”

Environmental control of Northeast Atlantic mackerel (Scomber scombrus) recruitment in the southern Bay of Biscay: case study of failure in the year 2000

“…Otolith samples for mackerel juveniles and pre-recruits were obtained from July to October 2000 from the commercial purse seine fleet and also from the bottom trawl survey. The microstructure analysis used 313 larval, 64 post-larval and 68 juvenile ⁄ pre-recruit otoliths, following the procedure described in Villamor et al (2004b). Age was estimated by interpreting and counting daily growth rings on the otoliths (sagittae).…”

“…It can be seen that no larvae born before the first storm were caught after the second storm (neither larvae nor postlarvae). As fish over 40 mm in length (about 45 days old; Villamor et al, 2004b) are not caught with the plankton net, from the sampling in the second cruise we can only account for the lack of larvae born in the 2 weeks before the first storm, and cannot know for sure whether older specimens were present. However, the sampling with purse-seine and trawl gears indicates a total absence of juveniles that hatched earlier than the first storm, which indicates that large post-larvae from early spawns did not actually survive.…”