Evidence of mutual benefits of nest association among freshwater cyprinids and implications for conservation

Abstract

1. Although nest association among Nocomis chubs and other minnows (Cyprinidae) is common throughout North America, the overall outcome of this relationship and its mechanisms of costs and benefits remain unclear. Because imperilment of stream fishes is affected by reproductive traits, the implications of this widespread interaction must be understood.2. Nest association mechanisms were explored using a multiple working hypotheses framework on fish assemblage data from 25 reaches in three tributaries of the New River, Virginia, USA. Multiple linear regression models predicting reproductive success (age-0 abundance) of chubs and associates were compared based on model weights (w i ) calculated from Akaike's Information Criterion, adjusted for small sample size (AICc), and relative change in AICc among models. For age-0 chubs, models represented hypotheses emphasizing the additive effects of adult abundance, nest abundance, and egg dilution by juvenile associates (causing decreased egg predation). For age-0 associates, models represented hypotheses emphasizing adult associate abundance, gravel substrate availability, nest abundance, parental care (as nest defence) from chubs, and egg dilution by chubs.3. Model evidence suggests that chubs can sustain themselves (w = 0.61), but their reproductive success is enhanced by a dilution effect from juvenile strong associates (w = 0.37). Strong associate reproductive success was best described by variables emphasizing nest association interactions (w = 0.46) and natural sources of habitat variability (w = 0.45), whereas that of weak associates was more closely related to availability of unmodified habitat (w = 0.50).4. Chubs and associates appear to receive a net benefit from the association, suggesting a mutualistic relationship. Community-wide conservation strategies may be useful for protecting symbiotic spawning fishes. In addition to competition and predation, conservation practitioners should consider positive interactions in conservation plans of imperiled mutualists.

Recognizing gape limitation and interannual variability in bluehead chub nesting microhabitat use in a small Virginia stream

“…However, unlike other studies of Nocomis nesting substrate preference (Lobb & Orth 1988;Wisenden et al 2009), we found little evidence of substrate preference À most likely because we accounted for gape size. Accounting for the gape size of adult male chubs drastically reduced the large differences between Peoples et al (2013) observed respective average differences (adjacent minus preferred) of 25.1 and 131 mm (for hornyhead and river chub N. micropogon, respectively) but measured adjacent substrate particles up to 70 and 680 mm, respectively. Our study excluded pebbles greater than 40 mm.…”

“…Nest associate reproduction often is closely tied to that of Nocomis (Wallin 1992). This spawning mode greatly influences associate reproductive success (Peoples & Frimpong 2013), geographic distribution (Pendleton et al 2012), and dispersal processes (Walser et al 2000;Hitt & Roberts 2011). Thus, protection of Nocomis spawning habitat benefits numerous species.…”

“…Nocomis nests are also used for spawning by over 35 other cyprinids, collectively termed 'nest associates' (Johnston & Page 1992). Nest associates benefit from the parental care provided to brood by the guarding male chub (Johnston 1994), and/or by the protective and physical characteristics of nests (Peoples & Frimpong 2013). Because substantial portions of local fish communities rely on them for spawning, Nocomis exert great influence on community structure (Walser et al 2000;Hitt & Roberts 2011), and are considered as keystone species in many systems (Vives 1990;Marcy et al 2005).…”

Nesting microhabitat comparison of Central stoneroller and Bluehead chub: potential inference for host-switching by nest associates

“…Nest building fishes can facilitate associate reproduction through the unique physical characteristics of their nests and by providing parental care to broods (Vives 1990;Johnston 1994a). Accordingly, whether or not a species exhibits nest associative spawning (or lack thereof) can have important implications for persistence in changing environmental conditions (Hitt & Roberts 2011;Peoples & Frimpong 2013). Because these facilitative mechanisms are likely to differ among hosts and associates, a better understanding of the microhabitat characteristics of nests of various hosts is a logical starting point for understanding host switching in this system.…”

A survey of macroinvertebrates colonizing bluehead chub nests in a Virginia stream

“…Over 30 cyprinid species have been documented using chub nests for spawning (Johnston & Page 1992). While the motive for other fish species using chub nests can vary and include egg predation, the spawning association of other species with Nocomis is widely considered mutualistic (Wallin 1992;Johnston 1994;Peoples & Frimpong 2013), making the chubs likely keystone species. The male chub cleans, guards, and buries the eggs against predators, thereby enhancing hatching success.…”