Importance of Nest and Paternal Characteristics for Hatching Success in Fathead Minnow
We quantified the importance of nest and paternal characteristics for survival of eggs of Fathead Minnow, a multiple-batch spawner in which breeding males guard and tend nests. We stocked experimental ponds three weeks apart and then intensively monitored 150 nests. Nest predation by conspecifics accounted for most of the egg mortality, and 29% of all nests failed to produce hatchlings. Although egg survival was not affected by date of stocking or nest initiation, hatching success improved in larger and longer-lasting nests. Nests where paternal care was observed during our monitoring were larger, lasted longer, and thus were more likely to produce hatchlings than nests where care-giving was not observed. Over one-third of the male caregivers displayed agonistic behaviors toward nest intruders, and this index of aggressive defense was also associated with improved nest performance. Larger males nested earlier and were more likely to be aggressive than smaller males. Post-spawning mortality of these larger, early-nesting males may facilitate a mid-summer demographic shift among breeders over the spawning season: nests of large, aggressive males are followed by those of smaller or later-maturing fish, who are more likely to survive to spawn again the following year.Abstract
(A, B) Relationships between hatching success and the date that nests first appeared during the spawning seasons of 2003 and 2004. (C, D) Relationships between hatching success and nest size and the duration of a nest. Data are grouped by stocking treatment (Early-Stock: solid shapes; Late-Stock: open shapes) and by year (2003: circles; 2004: squares).
Influence of nest care by male Fathead Minnows on (A) nest size and (B) nest duration. Nests were classified either as having no male guardian observed (No Care; n = 29), a male present (Passive Care; n = 78), or a male that aggressively protected its nest from intruders during egg counting (Aggressive Care; n = 43). Data are presented as x ¯ ± SE. Different letters denote groups that were significantly different (P ≤ 0.017) as determined from Tukey-Kramer multiple comparisons following a three-factor ANOVA.
(A, B) Catch per unit effort (CPUE; x ¯ ± SE) and (C, D) mean percentage composition of Fathead Minnows trapped biweekly in MBRS ponds in 2003 and 2004. For these graphs, data have been pooled across ponds and stocking treatment (2003: n = 3–6 pond-halves; 2004: n = 2–4 pond-halves). Data for Days 42 and 56 only exist for ES populations because of their longer residence in the ponds. At the end of the summer, all surviving fish were removed from the ponds for a final, total population assessment (Rmv).
Contributor Notes
Associate Editor: J. W. Snodgrass.