International Journal of Molecular Ecology and Conservation, 2025, Vol.15, No.3, 111-122 http://ecoevopublisher.com/index.php/ijmec 113 Spanish mackerel (S. maculatus) is distributed in the warm waters of the western Atlantic Ocean, such as the southeast coast of the United States, the Gulf of Mexico and the Caribbean Sea (Alrashada, 2022; Rothman et al., 2022). As migratory fish, different species of Spanish mackerel often have clear seasonal migration routes and spawning grounds. Figure 1 Digital X-ray images of Scomberomorus species (A-J) from the Northern Indian Ocean revealing the diversity, fork length (FL), and number of vertebrae (Adopted from Jeena et al., 2022) 2.2 Ecological habits and environmental adaptation characteristics As a high-speed swimming predatory fish, Spanish mackerel exhibits a series of unique ecological habits and environmental adaptation characteristics. They are usually pelagic or mid-pelagic fish, and are neritic-pelagic species that can move both in the nearshore continental shelf and in the open sea. Take the Japanese mackerel as an example. It is a typical surface-middle layer fish that migrates in the coastal waters of China and surrounding waters throughout the year and has a wide range of tolerance to water temperature and salinity (Muko et al., 2021; Ito et al., 2022). The Indo-Pacific mackerel often appears in coastal waters at a depth of 15 to 200 meters, and prefers turbid, low-salinity nearshore environments such as estuary salt-fresh water mixing areas (Joy et al., 2020; Widiasih et al., 2022). This ability to adapt to lower salinity environments enables it to enter estuaries and bays to feed on prey such as juvenile fish, reflecting a certain degree of euryhaline ecological adaptation. As a carnivorous fish, Spanish mackerel has swift swimming ability and predation skills. Its streamlined body, well-developed tail fin and muscles give it outstanding explosive power and cruising speed, enabling it to chase fast-moving bait fish. Spanish mackerel feed on small fish such as sardines and anchovies, and also prey on crustaceans and cephalopods such as squid, shrimps and crabs (Fatemi et al., 2017; Sui et al., 2021). The digestive and metabolic systems of Spanish mackerel are also adapted to its predatory and high-speed swimming lifestyle: for example, its muscles are rich in myoglobin and mitochondria to meet the oxygen and energy required for long-term cruising and high-speed sprinting; its tolerance and clearance of lactic acid are also strong, which can quickly restore physical strength after high-intensity exercise.
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