The yellowfin is a large tuna. Adults may reach 6 feet in length and weigh pounds. Yellowfin tuna live in all tropical and subtropical oceans except for the Mediterranean. The species is epipelagic , preferring deep offshore water above the thermocline in the top feet of the sea. However, the fish can dive to depths of at least feet. Yellowfin tuna are migratory fish that travel in schools. Movement depends on water temperature and food availability.
The fish travel with other animals of a similar size, including manta rays , dolphins, skipjack tuna, whale sharks , and whales. They commonly aggregate under flotsam or moving vessels. Yellowfin fry are zooplankton that feed on other zooplankton. As they grow, the fish eat food whenever it is available, only swimming more slowly when satiated. Adults feed on other fish including other tuna , squid, and crustaceans.
Tuna hunt by sight, so they tend to feed during daylight hours. Yellowfin tuna can swim up to 50 miles per hour, so they can capture fast-moving prey. The yellowfin tuna's speed is due partly to its body shape, but mainly because yellowfin tuna unlike most fish are warm-blooded.
In fact, a tuna's metabolism is so high the fish must constantly swim forward with its mouth open to maintain sufficient oxygenation. While fry and juvenile tuna are preyed upon by most predators, adults are sufficiently large and quick to escape most predators.
The pectoral fin is also long, reaching beyond the space between the dorsal fins. The caudal peduncle is very slender and includes three sets of keels. Seven to ten dorsal and ventral finlets are present. Scales are lacking behind the corselet, a band of large scales forming a circle around the body behind the head. A swim bladder is present. The eyes are small; teeth are small and conical. Similar species occurring in the same areas as yellowfin tuna include bigeye tuna Thunnus obesus , blackfin tuna T.
The bigeye tuna has shorter dorsal and anal fins than the yellowfin tuna and is generally a heavier and deeper-bodies fish. Blackfin tuna have dorsal and anal finlets that are dusky in color, rather than bright yellow with black margins as seen in the yellowfin and bigeye tunas.
Albacore can be distinguished from the yellowfin with the size of the pectoral fins. The pectoral fins of the albacore are much longer than the yellowfin tuna, reaching to the second dorsal finlet in most cases. Also the caudal fin of the albacore has a white posterior edge which is lacking on the yellowfin tuna. Coloration The body is metallic dark blue or greenish above, while the belly and lower sides are silvery white and crossed by many vertical, interrupted lines.
Perhaps most distinctly, a golden stripe runs along the side. The second dorsal and anal fins and finlets are bright yellow, and the finlets are bordered by a narrow band of black.
Size, Age, and Growth The maximum length reported for yellowfin is inches cm total length and the maximum weight is lbs. This latter example is more indicative of the common maximum size for the species. Food Habits Primary prey items include fish, cephalopods, and crustaceans.
Yellowfin appear to forage rather indiscriminately for any of these items. A study by Watanabe found 37 families of fish and 8 orders of invertebrates in yellowfin stomachs. Fish species consumed by the yellowfin tuna include dolphinfish , pilchard, anchovy, flyingfish, mackerel, lancetfish, and other tunas. Other prey items are cuttlefish, squid, octopus, shrimp, lobster, and crabs. Yellowfin are apparently sight-oriented predators, as their feeding tends to occur in surface waters during daylight.
Other large fish and marine mammals compete with yellowfin for food. Reproduction Size at maturity varies by region, and may also be different between individuals found near- and offshore.
Each night, they travel up to 9 miles offshore to feed and then return to the exact same spot the next day. Tagging studies on tunas in the open sea show similar behavior.
A tuna will hang around a floating log or other debris during the day, travel long distances at night, and return to the exact same log the next day. All species of tuna share some interesting biological characteristics. This is a huge advantage. For most cold-blooded fish, the colder the water and therefore their body is, the slower and more sluggish they are.
This allows them to swim faster and have increased endurance. No other fish can swim as far or as fast as tuna. Water has a great deal of resistance or drag, so every eight-fold increase in swimming speed takes a fold increase in energy. However, there are some populations that are fished more heavily than others, and it is important to continue to monitor these activities in order to prevent fishing levels that could threaten this iconic, powerful species.
In the s, fisheries that targeted the yellowfin tuna were responsible for accidentally catching and killing several million spotted and spinner dolphins and sparked the famous and successful dolphin-safe tuna campaign. The tendency of adult yellowfin tunas to school with similarly sized adult dolphins led to the unfortunate habit of fishermen setting their nets on dolphin pods with the hope of catching the nearby tuna.
That activity is now illegal in most places around the world. Yellowfin tuna get their name from the bright yellow color of their dorsal, anal, and tail fins. Female yellowfin tuna species can release up to 4 million eggs when spawning. Yellowfin tuna are known to travel in schools with different species, including skipjack and bigeye tuna.
Click here or below to download hands-on marine science activities for kids. Ocean Fishes Yellowfin Tuna Thunnus albacares.
0コメント