Temporal and geographic variability of sardine maturity at length in the northeastern Atlantic and the western Mediterranean

Abstract

Temporal and geographic variability of sardine maturity at length in the northeastern Atlantic and the western Mediterranean. e ICES Journal of Marine Science, 63: 663e676.We investigate spatial and temporal variations in sardine maturation patterns and discuss the implications for stock structure, using recent samples collected opportunistically across the species range and data collected regularly for the assessment of the Atlanto-Iberian stock. Maturity ogives were fitted to maturity-at-length data using Generalized Linear Models, and maturation patterns are summarized by length at first maturity (L 50 ). Sardine attain sexual maturity at a total length of 10.9e16.8 cm. The percentage of mature small sardine increases from north to south across the Northeast Atlantic. L 50 is low in the Mediterranean and Moroccan waters, but maturation is delayed towards the limits of the species' range. Sardine mature smaller in the Gulf of Cadiz than in other areas of the Atlanto-Iberian stock, although there is no indication of a different maturation pattern north of the stock boundary. These results are not sufficient to review the stock structure of sardine, but question the hypothesis of homogeneous biological properties of sardine populations within the stock area. Sardine maturation length reduced and the spawning period extended in western Iberia during the past two decades. Associated increases in fish condition and fat reserves during the summer feeding season suggest that variations in reproductive traits may have been caused by environmentally driven changes in food availability.

Essential habitat for sardine juveniles in Iberian waters

“…Estimates of sardine juvenile abundance (in number and biomass) were calculated following the procedures described in Simmonds and MacLennan (2005) and implemented in the "EchoR" package (Doray 2013) for R (R Development Core Team 2011). Based on sardine growth (Silva et al 2006), we assumed sardine juveniles observed each year to be survivors of eggs spawned the year before. Therefore, estimates of sardine juvenile abundance were made with the explanatory variables of year i with the corresponding variable egg abundance of the previous year (year i-1).…”

“…For sardine, a sub-sample of 100 individuals was taken and their total length (TL) and weight (W) were measured. In this study, juveniles were considered to be individuals with TL≤16.0 cm (Silva et al 2006). Sardine age-length keys show that individuals with TL≤16.0 cm broadly represent the recruiting year-class in spring surveys (age-1 individuals).…”

“…Sardine age-length keys show that individuals with TL≤16.0 cm broadly represent the recruiting year-class in spring surveys (age-1 individuals). Since sardine length at which 50% of the fish are mature (L 50 ) is around 14.0 cm in the study areas (Silva et al 2006), a small proportion of young adults are also included. …”

Environmental factors affecting anchovy reproductive potential in the southern coastal waters of Korea

“…The South Korean coastal waters are characterized by a wind-driven and strong tidal current in the shallow southwestern area and a weak tidal current in the relatively deep southeastern area (Na et al 1990;Bae & Kim 2012). Geographical patterns of maturation and fish condition are affected by environmental conditions (Roessig et al 2004, Silva et al 2006. However, few studies have been conducted on the research on geographical differences for the reproductive potential of the anchovy and their environmental factors in Korean waters.…”

Bathymetric segregation of spawning stages in the Atlantic sardine Sardina pilchardus

“…Sardines release multiple batches of pelagic eggs (Ganias et al 2004) through protracted spawning periods in which duration and timing display both latitudinal ) and size-related (Silva et al 2006, Ganias et al 2007 shifts. During the spawning season, population egg production is continuous, and each day a relatively small fraction (~10%; Ganias et al 2003) of the reproductively active population is reproducing, suggesting that at any given time active individuals are in various spawning states.…”