454
JAMES E. DEACON AND W. L MINCKLEY
It is notable that mosquitofish have been implicated in the decline of
many fish species, in North America and elsewhere (Myers, 1965). In light
of its essentially world-wide dissemination by man for use in mosquito control (Gerberich and Laird, 1965), it is likely that an untold amount of
damage has been done by this species, especially in faunally depauperate
areas. Mosquitofish may actively prey upon other fishes, however, rather
than compete with them for food or space.
Most desert fish populations were relatively devoid of parasites prior
to 1930 or so (Wilson et al, 1966; James, 1968); and a general correlation between introduction of alien fish species and an increase in incidence
of parasitic crustaceans on natives has been demonstrated. This may have
resulted from an initial introduction of the parasite along with stocked
fishes, and a high susceptibility of indigenous forms to its depredations,
or to a weakening of native fishes under competitive stress of exotics, or
both.
B. MODES OF REPRODUCTION AND DEVELOPMENT
Reproductive habits of fishes are receiving ever-increasing study by
physiologists, ethologists, and others, and a vast amount of information,
too voluminous to be reviewed here, is currently available. Breder and
Rosen (1966) include many references plus a broad synthesis of reproductive behavior in a systematic treatment. Carlander (1969) provided
an overall view of many life-history data for North American species, including information on fecundity, spawning times, etc. Physiological
aspects of reproductive cycles and sexuality have been covered in volumes
edited by Brown (1957), Hoar and Randall (1969), and others cited
therein.
1. Sexual Cycles and Behavior
In temperate zones, reproductive activities of fishes may be closely attuned to changes in photoperiod and temperature. As one moves toward
the tropics, other factors, such as seasonal rains, may provide triggering
reproductive stimuli. And, where conditions warrant year-round reproduction, energy demands for gamete production may dictate cyclical phenomena, at the individual level at least (Hoar, 1969). Fishes may also
develop unique reproductive cycles geared to their special habitats.
For example, some species, notably those of perennially turbid streams,
appear to spawn at whatever time in spring or summer the rivers reach
flood stage. Eggs and larvae of the Arkansas River shiner (Notropis
girardi) drift free near the water surface, and development is so rapid that
swimming initiates 3 or 4 days after hatching. Eggs deposited in the shifting, sandy bottom would be buried, and in backwaters they would be cov-
JAMES E. DEACON AND W. L MINCKLEY
It is notable that mosquitofish have been implicated in the decline of
many fish species, in North America and elsewhere (Myers, 1965). In light
of its essentially world-wide dissemination by man for use in mosquito control (Gerberich and Laird, 1965), it is likely that an untold amount of
damage has been done by this species, especially in faunally depauperate
areas. Mosquitofish may actively prey upon other fishes, however, rather
than compete with them for food or space.
Most desert fish populations were relatively devoid of parasites prior
to 1930 or so (Wilson et al, 1966; James, 1968); and a general correlation between introduction of alien fish species and an increase in incidence
of parasitic crustaceans on natives has been demonstrated. This may have
resulted from an initial introduction of the parasite along with stocked
fishes, and a high susceptibility of indigenous forms to its depredations,
or to a weakening of native fishes under competitive stress of exotics, or
both.
B. MODES OF REPRODUCTION AND DEVELOPMENT
Reproductive habits of fishes are receiving ever-increasing study by
physiologists, ethologists, and others, and a vast amount of information,
too voluminous to be reviewed here, is currently available. Breder and
Rosen (1966) include many references plus a broad synthesis of reproductive behavior in a systematic treatment. Carlander (1969) provided
an overall view of many life-history data for North American species, including information on fecundity, spawning times, etc. Physiological
aspects of reproductive cycles and sexuality have been covered in volumes
edited by Brown (1957), Hoar and Randall (1969), and others cited
therein.
1. Sexual Cycles and Behavior
In temperate zones, reproductive activities of fishes may be closely attuned to changes in photoperiod and temperature. As one moves toward
the tropics, other factors, such as seasonal rains, may provide triggering
reproductive stimuli. And, where conditions warrant year-round reproduction, energy demands for gamete production may dictate cyclical phenomena, at the individual level at least (Hoar, 1969). Fishes may also
develop unique reproductive cycles geared to their special habitats.
For example, some species, notably those of perennially turbid streams,
appear to spawn at whatever time in spring or summer the rivers reach
flood stage. Eggs and larvae of the Arkansas River shiner (Notropis
girardi) drift free near the water surface, and development is so rapid that
swimming initiates 3 or 4 days after hatching. Eggs deposited in the shifting, sandy bottom would be buried, and in backwaters they would be cov-