| Virginia
Journal of Science.
2001. Vol 52 (1) : 25-34 |
| Comparison
of Spawning and Non-spawning Substrates in Nests of Species of Exoglossum and Nocomis (Actinopterygii: Cyprinidae) Eugene G. Maurakis1,2 and Terre D. Green1 Science Museum of Virginia,1 2500 West Broad Street, Richmond, VA 23220 and Department of Biology,2 University of Richmond, Richmond, VA 23173 ABSTRACT
Percent composition of pebble size classes from spawning and
non-spawning substrates of nests were used to test the hypothesis that
distribution of pebble sizes is random in nests of Exoglossum laurae, Exoglossum maxillingua, Nocomis leptocephalus, Nocomis micropogon, Nocomis platyrhynchus, and Nocomis raneyi in Virginia.
In nests of the two species of Exoglossum,
spawning areas (i.e., upstream bases of nests) contain significantly
greater amounts of the 6.0 mm size class, and significantly smaller
amounts of the 2.5 mm size class of stones than do non-spawning
areas. Spawning areas (i.e., pits) in nests of N. leptocephalus contain
significantly more 6.0 mm pebbles than non-spawning areas, whereas
spawning areas (i.e., troughs) in nests of N. micropogon, N. platyrhynchus, and N. raneyi are composed of
significantly more 6.0 and 11.3 mm pebbles than non-spawning
areas. In all Nocomis
species, there was significant selection against the largest (23.0 mm)
size class of pebbles in spawning areas. Male Exoglossum and Nocomis expend significant amounts
of time reorganizing substrate material in spawning areas of their
nests before and during spawning. Reorganizing pebbles results in
relatively uniform sizes of substrate material at spawning areas in
nests of each species. We propose that selection of 6.0 and 11.3
mm size classes for spawning areas is related to spawning behaviors and
enhancement of survival of eggs and larvae in nests. Sizes larger than
11.3 mm interfere with spawning behaviors, and sizes smaller than 6.0
mm form a compacted substrate, which can crush eggs and larvae during
trough or pit reshaping, and impede water flow, and consequently,
aeration of eggs and larvae. |