Population structure of the chub mackerel (Scomber colias) in the North-east Atlantic inferred from otolith shape and body morphometrics

Abstract

The Atlantic chub mackerel (Scomber colias) is an important commercial fish species of the Northeast Atlantic. Two-year-old individuals collected between January and April of 2018 at six sampling locations (45 fish per site) of the Northeast Atlantic (Azores, Madeira, Canaries and mainland Portugal-Matosinhos, Sesimbra and Portimão) were used for body morphometrics and otolith-shape analyses. Data were analysed by univariate and multivariate statistics. Re-classification success using shape analyses and body morphometrics showed an overall rate of 51 and 74% respectively. Regional differences regarding the otolith-shape analyses suggested a single stock, not necessarily homogenous, with a discrete separation of two main groups (oceanic islands and mainland Portugal). However, body morphometrics showed a more detailed separation in two main groups (Canaries and the others, but with a slight differentiation between fish from Azores-Madeira and mainland Portugal). Moreover, joint analyses gave an overall re-classification success of 82% and allowed a more comprehensive scenario, showing the existence of three main groups (Canaries, Azores-Madeira and mainland Portugal). Regional differences are probably related with different oceanographic conditions influencing the feeding regime and fish growth. The hereby data suggest that S. colias caught in the Northeast Atlantic are different population units, and we recommend a fishery management at a finer regional scale.

Spatial variability of life-history parameters of the Atlantic chub mackerel (Scomber colias), an expanding species in the northeast Atlantic

“…Some genetic studies showed no significant differences between the Atlantic chub mackerel from the Mediterranean and eastern Atlantic areas (Scoles et al 1998, Zardoya et al 2004). However, significant regional differences have been found between smaller areas in the east Atlantic Ocean, including the Mediterranean Sea and Macarronesian islands, based on the analysis of morphology, meristic characteristics (Allaya et al 2016, Bouzzammit and El Ouizgami 2019, Muniz et al 2020) and associated parasites (Mele et al 2014). Muniz et al (2020), based on otolith morphology analysis, suggested the existence of one group in the northeast Atlantic islands (Azores, Madeira and the Canary Islands) and another one on the Iberian Portuguese coast.…”

“…However, significant regional differences have been found between smaller areas in the east Atlantic Ocean, including the Mediterranean Sea and Macarronesian islands, based on the analysis of morphology, meristic characteristics (Allaya et al 2016, Bouzzammit and El Ouizgami 2019, Muniz et al 2020) and associated parasites (Mele et al 2014). Muniz et al (2020), based on otolith morphology analysis, suggested the existence of one group in the northeast Atlantic islands (Azores, Madeira and the Canary Islands) and another one on the Iberian Portuguese coast. Correia et al (2021), according to microchemical analysis of the same otoliths, suggested the existence of at least four stock components in the northeast Atlantic (Azores, Madeira, Canary Islands and Iberian Portuguese coast).…”

“…Genetic, morphologic and parasite studies have shown significant differences between Atlantic chub mackerel from the western Atlantic and the eastern Atlantic (Scoles et al 1998, Roldán et al 2000, Costa et al 2011, supporting the existence of two different populations at either side of the Atlantic Ocean. However, whether this species constitute a single stock or not in the eastern Atlantic is still unknown, as the studies performed in this area provide conflicting results (Scoles et al 1998, Mele et al 2014, Muniz et al 2020). The information available on the northeast Atlantic suggests that in both African and European waters the species migrates from the wintering areas (mainly located in Mauritanian waters, southern Portugal and the inner part of the Bay of Biscay) towards northern waters in summertime and, in the case of the Bay of Biscay, towards the western Iberian Peninsula (ICES 2021a).…”

Host lifestyle and parasite interspecific facilitation mediate co-infection in a species-poor host-parasite system

“…Following the pattern of their clupeid hosts, no clear differentiation across the North-South axis of LT was found (Kmentová et al, 2020). To study the ecosystem dynamics in the pelagic zone, surveys of pelagic fishes have been combined with analyses of their morphological variation (Muniz et al, 2020; Valentin et al, 2014), otolith composition (Javor et al, 2011) and, more recently, population genomics (Baltazar-Soares et al, 2018; De Keyzer et al, 2019; Junker et al, 2020). This holistic approach has been proposed not only to study spatiotemporal dynamics in the pelagic zone (Abaunza et al, 2008; Kerr et al, 2017), but also other aquatic ecosystems such as large rivers (Lavoué et al, 2008).…”

Comparing otolith shape descriptors for population structure inferences in a small pelagic fish, the European sardineSardina pilchardus(Walbaum, 1792)

“…Currently, two main shape descriptors are widely and routinely used: Elliptic Fourier transform and Discrete Wavelet transform. The Elliptic Fourier descriptor (EFd) routine for describing the otolith shape has been the most used in the latest decades ( e.g ., Bird et al ., 1986; Doering & Ludwig, 1990; Jemaa et al ., 2015a; Mapp et al ., 2017; Moreira et al ., 2019; Muniz et al ., 2020; Neves et al ., 2021), which provides functions in terms of sines and cosines of the otolith contour representation (Libungan & Pálsson, 2015a) characterising the otolith shape. This representation allows pattern recognition and classification ( i.e ., otoliths with similar Fourier decomposition would share similar shape characteristics) (Parisi‐Baradad et al ., 2005).…”