Friday, September 11, 2009

A Black Jack cruises over McDonald's Reef, Grand Turk

This is a Black Jack. Black Jacks are fish that live in the open ocean and that are seen over the reef only occasionally. Black Jacks can be identified by their size, the color of their tail fins, and the size of their dorsal and anal fins. Black Jacks can be up to 3 feet long. This is slightly bigger than many other types of jacks. All jacks have a similar shape. But the Black Jack has a two color (black and white) tail fin, and has long dorsal and anal fins. The dorsal fin is the fin on top, and the anal fin is the fin on the bottom near the tail. The tail fin is also called the caudal fin. Notice this Black Jack has long, yellow pectoral fins, the fins near its gills on either side of its body. Although often a silvery gray color, Black Jacks can change their color to a dark brown or black.
Black Jacks are built for speed. They have a steeply sloping forehead and a body that tapers down to a narrow tail. The Black Jack's tail is deeply forked and swept back from its body. The Black Jack's shape reduces drag, and its tail is shaped for propulsion. The Black Jack is a hunter that catches other fish. It uses its speed to chase and catch its prey. They often swim alone, but may also hunt in small groups.
Black Jacks are fish of the open ocean. Their silver color gives them fairly good camouflage in open water. Many fish of the open ocean are silver colored, unlike the brightly colored fish that live near the reef. Black Jacks can be found over 1200 feet deep. Even though they are usually found in deep water in the ocean, they may sometimes swim near the reef. This fish was cruising along the top of the wall of the reef near the island of Grand Turk. It was curious about the divers in the water, and made one pass to check us out before it cruised off into the deep. It swam close to me, giving me a chance for this great photograph. This Black Jack was 3 feet long, which is about as big as these fish get.
Black Jacks are found all around the world in tropical waters.
Back to ReefNews Photo Gallery Volume 4
Copyright © 1999, ReefNews ®, Inc. 95 Obsidian Loop Los Alamos, NM 87544