The Fishes: Erythrinidae

CYPRINIFORMES - carps and characins: Page 1

Family: Erythrinidae

Family: Ctenolucidae

Erythrinidae
A group of primitive Characiformes. They are predatory fish living along the edges of streams, lakes and within flooded forest. All are adapted to low oxygen conditions. The three common species are Erythrinus erythrinus, Hoplias malabaricus and Hoploerythrinus unitaeniatus. A considerably rarer species is Hoplias macrophthalmus which is known as the giant trahira and can reach 80 cm in length.

Erythrinus erythrinus
This is a small erythinid reaching a maximum adult length of about 20 cm. It is common in the margins of floodplain lakes and small forest pools where it lies concealed waiting for suitable prey to attack. It feeds on insects, prawns and small fish. During the dry season when forest pools dry out this species can move across the forest floor to enter a new pool or stream.

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Lateral view of adult Erythrinus erythrinus caught in flooded forest

Hoplias malabaricus
H. malabaricus is widely distributed in the Amazon basin and is common in both black and white water lakes and blackwater streams. It attains a maximum length of about 50 cm and is a powerful fish which can produce a painful bite. It is a ambush predator that waits quietly under cover until suitable prey comes close. I have seen people with wounds inflicted by this species and one local who was working with us was bitten on the heel while wading bare footed through flooded forest. The Hoplias darted out from under some leaves and attacked his foot. This species is an aggressive predator which takes a wide variety of prey. Larger individuals are piscivores, the food items found in the guts of specimens in the floodplain near Tefe at high water are shown in the table below.

Hoplias malabaricus gut contents (P=Present)
INDIVIDUAL NUMBER	1	2	3	4	5	6
LENGTH (cm)	10.1	13.8	12.6	9.7	6.6	5.6
MASS (g)	12	42	34	12	2	2
PISCES-FLESH	P
PISCES-BONES	P
PISCES-SCALES	P			P
PISCES-FINS	P			P
EMPTY		P	P		P	P

H. malabaricus is one of the commonest fishes found on the margin of flooded forest and within floating meadow. The size and weight distributions of specimens caught in white water lakes are shown in the figures below. They are a tough species well adapted to low oxygen levels. Because of their aggressive behaviour and tendency only to leave cover when the light is low they are unsuitable pets for home aquarists.

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Length/frequency distribution of Hoplias malabaricus, October 1994	Hoplias malabaricus, lengths & weights, October 1994	Hoplias malabaricus, lengths & weights, March 1995 & October 1994	Hoplias malabaricus, lengths & weights, March-July 1995
	Hoplias malabaricus, recorded lengths & weights, October 1994	A specimen of Hoplias malabaricus caught in the margin of a floodplain lake

Hoploerythrinus unitaeniatus
This species is smaller than Hoplias malabaricus, reaching a maximum length of about 40 cm. It is a general predator and scavenger which normally eats insects and other arthropods.

Hoplerythrinus unitaeniatus gut contents (P=Present)
INDIVIDUAL NUMBER	1	2	3	4	5	6	7	8	9	10
LENGTH (cm)	14.5	14.3	16.5	15	17.2	19.5	15.5	18	15	15
MASS (g)	60	58	88	66	102	154	70	110	70	64
AVES - BONES			3
REPTILIA									P
PISCES-SCALES						1
ARACHNIDA					P		1
COLEOPTERA		1
ISOPODA									1
DIPTERA	1
LEPIDOPTERA				1
ODONATA							2
ORTHOPTERA				P				P	P
CECROPIA LOTILOBA								190
EMPTY										P

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Lateral view of preserved adult Hoploerythrinus unitaeniatus caught in a floodplain lake near Tefe

Ctenolucidae
A small family of elongate-bodied predatory fish belonging to the Characiformes. They are distinguished by their elongate form with the dorsal and anal fins set well-back and close to the tail. They have sharp, conical teeth set in a single row. They are common in varzea and blackwater lakes.

There are two described genera within this family, Boulengerella and Ctenolucius. Both genera comprise elongate, piscivorous fish so as a typical example of the form we include details of Boulengerella maculata.

Boulengerella maculata
This is a slender pike-like piscivore that can attain almost 70 cm in length. In Brazil it is called Peixe-agulh�o, literally needle fish, because of its elongate form. The jaws hold sharp, curved, conical teeth and the upper jaw has a characteristic extended tip. It is an open water predator of fish and is found in both white and black water lakes.

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Boulengerella maculata - Recently caught specimens from a white water lake near Tefe	Lateral view of a preserved specimen of Boulengerella maculata. Note the characteristic cartilagenous extension to the upper jaw