Reproductive cycle of the blue jack mackerel,Trachurus picturatus(Bowdich, 1825), off the Portuguese continental coast

Abstract

This work provides for the first time a description of the reproductive biology of Trachurus picturatus in Portuguese continental waters (between 41° 49′ and 36° 57′ latitude North). From January 2010 to December 2016 a total of 7409 individuals were sampled from bottom trawlers operating on the northwestern coast of Portugal. The observed sex ratio was 0.56 in favor of the females. Monthly variations in gonadosomatic index, proportion of actively spawning individuals, hepatosomatic index and Fulton′s condition factor were analyzed. More than 60% of spawning individuals were recorded in the first quarter, corresponding to the highest values of GSI, and Fulton's K and hepatosomatic index increased after the start of spawning. The morphometric relationships between total length and gutted weight showed significant correlations (high determination coefficient, r2 > 0.9) and isometric growth (b = 3) for both sexes. Results indicate that the spawning season of T. picturatus starts in December and extends until April–May, with a peak in March, which agrees with what has been indicated by other authors for the northeast Atlantic. This work provides important biological information on a species that although not subject to stock assessment is currently the 5th species landed by weight in Portuguese continental waters.

Importance of Depth and Artificial Structure as Predictors of Female Red Snapper Reproductive Parameters

“…Conversely, the best predictions of ovarian development were seen for reproductively active versus inactive females, with OOB error of only 10.72%, implying that a combination of GSI, month, FL, and depth can accurately distinguish reproductive activity. Our model supports previous work, which has suggested that simply assigning an active or inactive classification to fish can aid managers in identifying spawning seasonality or even spawning location (e.g., Lowerre‐Barbieri et al 2015; Brown‐Peterson et al 2017; Costa 2019). Finally, month became less important than FL when predicting the spawning activity of reproductively active fish.…”

Length-weight relationship and condition factor of Trachurus trachurus found in the central-east region of the Moroccan Mediterranean

“…Fulton's condition factor (K), also known as the length-weight factor, is used to determine the physiological state of a fish, including its reproductive capacity and sexual maturity as well as the influence of the environment (degree of nutrition) on the species (Costa, 2019;González-Kother et al, 2020). The condition factor is determined by the ratio relating the weight and the length of the fish according to the following formula: K = (TW/TL 3 ) x 100…”

“…Fulton's condition factor (K) is used to estimate seasonal changes in fatness under the influence of external (environment) or internal (physiological) factors (Costa, 2019).…”

Negative impact on the reproductive potential of blue jack mackerel Trachurus picturatus by Kudoa infection of the ovary

“…Landings in the mainland Portuguese coast, although highly variable, reached an average value of ca 2800 tonnes/yr in the last decade. Despite its growing economic importance, there is few information on the reproductive strategy of the blue jack mackerel, apart from data on size at maturity and spawning season in the Portuguese continental coast (Costa 2019), Azores (Garcia et al 2015) and Canary Islands (Jurado-Ruzafa & Santamaría 2013), and the type of fecundity for Madeira Island (Vasconcelos et al 2017).…”