Diet and trophic position of two mackerel species in the archipelago of Madeira, Portugal

Abstract

The Atlantic chub mackerel Scomber colias and the blue jack mackerel Trachurus picturatus are two abundant species in the Macaronesia region which includes the archipelago of Madeira, Portugal. Both are key species in the trophic web, being important prey for several local top predators, such as seabirds and marine mammals. Nonetheless, little is known about their feeding ecology in oceanic environments. In this study, the authors describe the seasonal variation in the diet of S. colias and T. picturatus in the oceanic region of Madeira throughout a year. Visual inspection of stomach contents revealed that S. colias fed on a broader range of prey groups than T. picturatus, but for both species, zooplankton (particularly calanoid copepods) and fish were the most important food items. The diet of S. colias included a higher proportion of fish, namely Atlantic saury Scomberesox saurus and S. colias, than that of T. picturatus, that included mostly the longspine snipefish Macroramphosus scolopax. T. picturatus consumed a higher proportion of decapods and other copepods. Seasonal variation was found in the diet of both species, with zooplanktonic species being more important in colder months (February to April) for S. colias and during warm months (May to October) for T. picturatus. Their diet in other seasons was dominated by fish. Although they consume similar prey, carbon and nitrogen stable isotope analysis of muscle of S. colias and T. picturatus showed little overlap in their diets, and T. picturatus showed higher δ15N and a narrower isotopic niche.

Interspecific relationships in a suboptimal habitat, an unexpected ally for the survival of the threatened Tenerife speckled lizard (Gallotia intermedia)

“…These resources displayed δ 13 C levels of approximately -18‰, which are markedly different from the δ 13 C levels of C3 plants (∼ -24‰) and C4/CAM plants (∼ -14‰). These levels indicate that the carbon is sourced from marine and epipelagic food sources in the area, such as epipelagic fishes like Trachurus picturatus and Scomber colias , which have δ 13 C values ranging between - 19‰ and -20‰ (Romero et al, 2021). In a similar manner, the δ 13 C values of G. intermedia (∼ -20 ‰) are indicative of this marine epipelagic δ 13 C signature.…”

Seasonal variation in microplastics and zooplankton abundances and characteristics: The ecological vulnerability of an oceanic island system

“…These species occupy intermediate trophic levels and are key prey species in the pelagic food web for many predators, such as tunas (e.g., Romero et al, 2021b), seabirds (e.g., Alonso et al, 2014) and cetaceans (Burkhardt-Holm and N'Guyen, 2019). Furthermore, they have a substantial commercial value, are widely consumed by the local population, and are often used as bait in tuna fishing (Hermida and Delgado, 2016;Tejerina et al, 2019;Romero et al, 2021b). Plastic ingestion by these key species would lead to the trophic transfer of such contaminants to pelagic apex predators and ultimately to humans.…”

“…Such a period coincides with the occurrence of some large pelagic predators, which feed mainly on epipelagic planktivorous fishes. For example, skipjack tuna (Katsuwonus pelamis) and the bigeye tuna (Thunnus obesus) constitute important commercial species in the region, and they occur seasonally in the warmer summer and early autumn months, mainly between June and October (Romero et al, 2021b). The diet of these species is based mainly on epipelagic fishes, such as blue jack mackerel (Trachurus picturatus) and Atlantic chub mackerel (Scomber colias) (Romero et al, 2021b).…”

“…For example, skipjack tuna (Katsuwonus pelamis) and the bigeye tuna (Thunnus obesus) constitute important commercial species in the region, and they occur seasonally in the warmer summer and early autumn months, mainly between June and October (Romero et al, 2021b). The diet of these species is based mainly on epipelagic fishes, such as blue jack mackerel (Trachurus picturatus) and Atlantic chub mackerel (Scomber colias) (Romero et al, 2021b). Other large predators, such as delphinids and baleen whales, which feed mainly on small pelagic fishes, also occur in the area in high numbers during these months (Alves et al, 2018;Fernandez et al, 2021).…”