Lactarius lactarius

The false trevally (Lactarius lactarius) is a species of fish in the family Lactariidae, currently the sole member of the family. False Trevally, a silvery-blue false trevally fading to silvery-white below with a dusky blotch on the upper part of the gill cover and yellowish fins.

Identifying Features

Body Shape:

• The false trevally has a compressed, elongated, and oval-shaped body. The body is somewhat deep and laterally flattened.

Coloration:

• The body is typically silvery-white or pale in color. The fins may have a yellowish tint, particularly the pectoral fins.

• Juveniles often display vertical bars on their sides, which may fade as they mature.

Head and Mouth:

• The head is relatively small, with a pointed snout. The mouth is terminal, located at the front of the head, and is slightly oblique.

• The eyes are moderately large.

Fins:

• The dorsal fin is continuous, with the anterior part consisting of spines and the posterior part with soft rays.

• The anal fin is relatively short, with a similar structure to the dorsal fin.

• Pectoral fins are long and often pointed, while the pelvic fins are shorter.

Unique Features

Lactating Glandular Structures:

• The false trevally has specialized glandular structures that secrete a milky substance, possibly as a defense mechanism, which is quite unique among fish.

Scales:

• The scales are small, smooth, and easily detached, giving the fish a slippery feel.

Forked Caudal Fin:

• The caudal fin is deeply forked, which aids in fast swimming.

Morphology

Size: 

• False trevally typically reaches a length of about 20-30 cm, though it can grow larger in favorable conditions.

Body Proportions: 

• The body is about 2-3 times as long as it is deep, and the head is about 4-5 times in total body length.

Teeth: 

• Teeth are small and pointed, arranged in bands on the jaws.

Reproduction

Spawning:

•  False trevally is believed to spawn in shallow waters, with eggs and larvae being pelagic (free-floating) in nature.

Sexual Maturity:

•  The fish reaches sexual maturity relatively early, which is an adaptation to its environment where predation pressure might be high.

Breeding Season:

•  Typically, breeding occurs during warmer months, though specific times may vary depending on the geographical location.

Habitat

Geographical Distribution: 

• Found across the Indo-Pacific region, from the eastern coast of Africa to Southeast Asia, and even as far as northern Australia.

Preferred Environment:

• False trevally favors coastal environments, often residing in estuaries, lagoons, and shallow bays.

• They are commonly found over sandy or muddy substrates where they can search for food.

• They can tolerate a range of salinities, which is why they are frequently found in estuarine environments.

Diet:

• These fish are omnivorous, feeding on small invertebrates like crustaceans, mollusks, and sometimes plant material or detritus.

Ecological Role

Trophic Level: 

• As an omnivorous species, false trevally plays a role in both predator and prey dynamics within its ecosystem. It helps control populations of smaller invertebrates and serves as prey for larger fish and marine birds.