The Biology and Culture of Tilapias

question, instead of activation, insemination, or fertilization. Our system

allows us to recognize the comparable intervals for any species, and thus to

make meaningful (biological) comparisons of life history styles across

virtually all organisms (Balon 1975a, 198la; Noakes 1981).

/ Reproductive Guilds

The second basic point for our discussion is the earlier (Balon 197513,

1975c, 1978; Balon et al. 1977) proposal to define fishes according to

reproductive guilds. Again, this has been described in detail elsewhere, and so

will be outlined here only in summary fashion. Basically, the assumption is

that the reproductive style, or guild, of each species will be determined by

factors relating to oxygen supply for the developing young, and predation

upon them (Kryzhanovsky 1956; Soin 1968). The full set of proposed guilds

will not be discussed here, only the major categories (again, this system is

hierarchical). The most inclusive category. the section, contains a number

/of sub-sections, each of which contains the individual reproductive guilds.

There are three sections; nonguarders, guarders and bearers. Within these

are, respectively: open spawning nonguarders and brood-hiding nonguarders,

substratechoosing guarders and nest-spawning guarders, and external and

internal bearers (Table 1).

Table 1. Reproductive guilds of fishes (after Balon 1975b), with most guilds omitted for

the sake of brevity.

Section Subsection Guild

A. Nonguarders A.l Open spawners A.l.l Pelagophils

A.1.6 Psammophils

A.2.1 Lithophils

A.2.5 Xerophils

B. Guarders B.l Substrate-choosers B.l.l Lithophils

B.1.4 Pelagophils

C. Bearers

B.2.1 Lithophils*

B.2.2 Phytophils*

B. 2.3 Psammophils*

B.2.5 Speleophils*

B.2.8 Actiniariophils*

6.1 External

C.2 Internal

C.l.l Transfer brooders

C.1.3 Mouthbrooders*

C.1.6 Pouch brooders

C. 2.1 Ovi-ovoviviparous

C.2.3 Viviparous

*Indicates guild known to contain cichlid species.