Transcript Fisheries and Aquaculture Management_Lecture

Fisheries and Aquaculture Management
Lecture 3:
Haplochromis of Lake Victoria
Introduction
 In the last two decades interest in the phylogeny of the
African Cichlidae has greatly increased
 Amongst the East African cichlids, the haplochromines of
Lake Victoria have become a focus of attention because
their ecosystem has been irreversibly changed by the
introduction of the Nile perch (Lates niloticus)
 Among the three great African Lakes, Lake Victoria, the
source of the Nile, was the last to be discovered by
Europeans.
 Not until thirty years after its discovery by John Harming
Speke in 1858, were the first fish specimens from Lake
Victoria brought to Europe by G.A. Fisher.
Introduction
 F. Hilgendorf (director of the Berlin Museum) was the first
zoologist to examine and describe this collection.
 Among the 19 specimens, probably collected at the shores
of the southern (= "German") part of the lake, were eight
specimens belonging to the Cichlidae (then known as
Chromidae).
 Hilgendorf (1888) (erroneously) described two specimens
as Chromis niloticus Linnaeus, 1758 (= Oreochromis
niloticus) and placed the remaining six specimens in five
new species.
Introduction
 For the generic placement of the new species Hilgendorf
followed Günther (1862) and Bleeker (1868).
 In the second part of his revision of the Cichlidae, in which
the number of African genera was raised to 19 (due to the
examination of the Moore collection from Lake
Tanganyika), Boulenger (1899) considered Haplochromis
and Ctenochromis to be synonyms of Tilapia
 The classification of the very numerous African members
of this family presents the greatest difficulties, and the
division into genera is unsatisfactory and open to criticism.
Introduction
 The species descriptions of Greenwood, the first
ichthyologist involved in field-work on Lake Victoria,
were quite different from preceding ones.
 They were characterized not only b y the fact that the
descriptions of the external morphology, gill rakers, oral
and pharyngeal teeth and preserved coloration were
much more detailed, but they also contained
information on the ecology, e.g. habitat, breeding and
food, and often, on live coloration.
 All new species of haplochromine cichlids from lake
Victoria described by Greenwood et al. (1957-1978)
were placed in the genus Haplochromis.
Characters used in the definition of haplochromine genera
 External characters mentioned in the earliest descriptions of
haplochromine genera were:
 body shape (compressed, elongate, oblong);
 number of dorsal and anal spines;
 scale type (cycloid or ctenoid); scale size (small, moderate,
large);
 squamation of cheek and gill cover.
 Dental characters which were used were: tooth shape
(canine, monocuspid, bicuspid, or tricuspid); tooth size;
number of tooth rows.
 Gill raker shape and size (short, medium sized, moderately
long) was used as well.
 Later on the number of vertebrae and the exposure of the
maxilla were added.
 Boulenger (1902) mentioned tooth curvature and the
movability of the teeth.
Taxonomy of Lake Victoria haplochromine cichlids in general
 Size range of adults 5-25 cm standard length.
 One nostril on each side of the snout.
 The dorsal fin, comprising a spinous and a soft rayed part, is
continuous.
 The lateral line is interrupted.
 From tilapiine cichlids, which share the foregoing characters,
haplochromine cichlids are distinguished by the following
features.
 The scales on the flank and caudal peduncle are ctenoid (feel
rough to the touch).
 Adult males have brightly coloured egg dummies on the anal fin.
 The "tilapia mark" at the base of the dorsal fin, which characterizes
the juveniles (up to 10 cm) of the tilapiine cichlid species in Lake
Victoria, is absent
 Until Greenwood's revisions, apart from the
monotypic genera, the only generic name which
was introduced especially for Lake Victoria cichlids
was Haplochromis.
 Originally proposed by Hilgendorf (1888) as a
subgenus of Chromis in the description of Chromis
(Haplochromis) obliquidens, it was raised to the
generic level by Boulenger (1906) to accommodate
cichlid species from Lake Victoria with teeth
intermediate between those of Paratilapia (outer
rows with conical teeth) and Tilapia (outer rows
with bicuspid teeth).
Genera in haplochromine taxonomy
 In a discussion on the generic or specific value of
morphological characters, only dental characters and
the number of anal fin spines were considered of
being valuable for the generic classification.
 The unravelling of the phylogenetic relationships with
in Haplochromis became a major research subject.
 Later research based on cladistic principles indicated
that the haplochromine species of Lakes Victoria,
Edward, George, and Kivu had to be considered
together
The following definition of Haplochromis may be used:
 Lacustrine, maternal mouthbrooding Cichlidae naturally
occurring in the Lake Victoria basin, with a Haplochromis
type of pharyngeal apophysis, i.e. with the basioccipital
contributing to the articulation facet for the upper
pharyngeal bones as well as to the support of that cranial
facet (Greenwood, 1978).
 The teeth of the outer row of the oral jaws are unicuspid,
bicuspid or tricuspid. In many species a mixture of these
types is found.
 When tricuspids are present they are usually most
numerous in the caudal part of the jaws.
Definition of Haplochromis (Contd’)
 Teeth of the 1-11 inner rows are unicuspid and/or tricuspid,
exceptionally bicuspid, usually of a smaller size than the
outer row teeth.
 The pharyngeal jaws may vary from thin and slender to
massive and strong.
 Pharyngeal teeth vary from slender to molariform and from
pronounced to bevelled or hooked (Barel et al., 1977).
 Usually there is a distinct sexual dimorphism in coloration;
the males being the more colourful sex.
 On the anal fin of males 1-9 distinct egg dummies are
present. The anal f in with 3 spines.
Proposal to stabilize nomenclature
 Until now morphological investigations have failed to give
us a clear picture of the phylogenetic relationships among
the Lake Victoria haplochromines.
 However, there are at least indications from both
morphological (scale and squamation) characters
(Lippitsch, 1993) and molecular data (Sage et al., 1984;
Meyer et al., 1990) that the Lake Victoria (super) flock is a
monophyletic group.
Reproduction
Brood care
 All species show some form of parental care for both
eggs and larvae, often nurturing free-swimming young
until they are weeks or months old.
 Parental care falls into one of four categories:
1. Open (Substrate) brooding
 Open or substrate brooding cichlids lay their eggs in the open,
on rocks, leaves, or logs.
 Male and female parents usually engage in differing brooding
roles.
 Most commonly, the male patrols the pair's territory and repels
intruders, while females fan water over the eggs, removing the
infertile and leading the fry while foraging.
 However, both sexes are able to perform the full range of
parenting behaviours.
Reproduction Contd’
2.
3.
4.
Cave brooding
 Secretive cave spawning cichlids lay their eggs in caves,
crevices, holes, or discarded mollusc shells, frequently
attaching the eggs to the roof of the chamber.
 Free-swimming fry and parents communicate in captivity and
in the wild.
 Frequently this communication is based on body movements,
such as shaking and pelvic fin flicking.
 In addition, open and cave brooding parents assist in finding
food resources for their fry.
Ovophile mouthbrooding
 Ovophile mouthbrooders incubate their eggs in their mouths as
soon as they are laid, and frequently mouthbrood freeswimming fry for several weeks.
Larvophile mouthbrooding
 Larvophile mouthbrooders lay eggs in the open or in a cave and
take the hatched larvae into the mouth.
 Mouthbrooders, whether of eggs or larvae, are predominantly
females.
Mating
 Cichlids mate either monogamously or polygamously.
 The mating system of a given cichlid species is not consistently
associated with its brooding system.
 For example, although most monogamous cichlids are not
mouthbrooders, Chromidotilapia, Gymnogeophagus, e.t.c. are all
monogamous mouthbrooders.
 In contrast, numerous open or cave spawning cichlids are
polygamous; examples include Apistogramma, Lamprologus e.t.c.
Population status
 In 2010, the International Union for Conservation of
Nature classified 184 species as vulnerable, 52 as
endangered, and 106 as critically endangered.
 At present, the IUCN only lists Yssichromis sp. Nov.
“argens” as extinct in the wild, and six species are listed
as entirely extinct, but it is acknowledged that many
more possibly belong in these categories (for example,
Haplochromis aelocephalus, H. apoogonoides, H. dentex,
H. dichrourus and numerous other members of the
genus Haplochromis have not been seen since the
1980s, but are maintained as Critically Endangered in
the small chance that tiny but currently unknown
populations survive).
Population status (Contd’)
 Because of the introduced Nile perch
(Lates niloticus) and water hyacinth,
deforestation that led to water siltation,
and overfishing, many Lake Victoria
species have been wiped out or
drastically reduced.
 By around 1980, lake fisheries yielded
only 1 percent cichlids, a drastic decline
from 80 percent in earlier years.
 About two-thirds of endemic cichlids
(approximately 300 species), especially
bottom feeders, became endangered or
extinct.
 Some survivors have adapted by
becoming smaller or hybridizing with
other species.
Haplochromis latifasciatus is
critically endangered