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COPYRIGHT 2005 Southern California Academy of Sciences
Abstract.--Seasonal and ephemeral color patterns in the kelp bass, Paralabrax clathratus, were studied on Santa Catalina Island, California from April 2000 to September 2002. Adults were monochromatic for part of the year (calico phase) and sexually dichromatic from April to October, with most adult males adopting bright orange snouts (OS phase). The seasonal occurrence of the OS phase in males overlapped with the spawning season, and the color was limited to ripe males. The OS phase in ripe males may function as a signal of sexual identity and sexual readiness to females. Both males and females exhibited distinct color patterns during courtship and spawning periods. During these periods, males were charcoal colored with dark black bars overlaying white spots (checkered phase), and females were often black with no visible spots (dark phase). Color patterns displayed by adults during spawning activities may facilitate mate signaling and the formation of spawning groups. Specific color patterns were also observed in relation to habitat and aggressive behaviors.
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Fishes are unique among vertebrates in their ability to display a wide variety of permanent and temporary color patterns, which are believed to be important in both social and environmental interactions (Townsend 1929; Cott 1940; Lorenz 1962). Some species exhibit permanent sexual dichromatism, where different color patterns are adopted for each sex and retained for life (DeMartini 1985; Kodric-Brown 1998). Conversely, monochromatic fishes often exhibit patterns of seasonal sexual dichromatism during the spawning season, and these color patterns are only adopted by actively breeding individuals (Thresher 1984; Kodric-Brown 1998). Ephemeral color changes, which usually persist for only brief periods of seconds to minutes, are widespread among fishes and occur under a variety of conditions including courtship, agonistic interactions, feeding, and changes in habitat (Losey 1976; Thresher and Moyer 1983).
Color patterns have often been used as key characters for identifying species within the family Serranidae (Heemstra and Randall 1993). Permanent dichromatism has not been described in the Epinephelinae but is common in the Anthiinae in association with sex change and sexual dimorphism (Shapiro 1981). Among serranines, permanent dichromatism has been reported in at least two species, black sea bass, Centropristes striatus, and barred serrano, Serranus psittacinus (Lavenda 1949; Hastings and Petersen 1986). Seasonal and ephemeral color changes in serranids are well known and are most commonly associated with the social behavior (i.e. courtship, aggression) of groupers (Colin 1992; Gilmore and Jones 1992; Sadovy et al. 1994), and color change has also been related to habitat (Townsend 1929; Smith 1971; Nemtzov et al. 1993). Investigations of color changes and associated behavior in serranines have focused mainly on two genera, Serranus and Hypoplectrus, both of which have tropical distributions (Clark 1959; Thresher 1984; Hastings and Petersen 1986).
Color patterns and associated behaviors of temperate serranines are poorly understood, although brief descriptions of sexual dichromatism have been reported in the genus Paralabrax. Male P. maculatofasciatus (spotted sand bass) adopt a pale body color with white chins during the spawning season, where as females become darker in coloration with yellow chins (Allen et al. 1995). During spawning, male P. maculatofasciatus often adopt a high-contrast body coloration consisting of dark vertical bars overlaying a white body background (Miller 2004). In P. nebulifer (barred sand bass), breeding males are a high-contrast gray and white color, and they develop golden-yellow crescents below their eyes that are not well developed in females (Allen and Hovey 2001). Other members of the genus exhibit permanent sexual dichromatism. Adult male P. loro (parrot sand bass) have bright orange dorsal fins and cheeks, and the females have red dorsal fins and cheeks (Thomson et al. 2000).
The functional significance of color change has not been examined in most serranids, including members of the genus Paralabrax, although color changes are believed to serve a similar purpose in all. Temporary color changes, whether seasonal or ephemeral, are usually associated with specific behaviors, where they function as social signals of motivation (Losey 1976; Thresher 1984; DeMartini 1985). Moreover, distinct color patterns, when coupled with courtship behavior, may enhance the conspicuousness of the color, thereby serving to attract the attention of potential mates (Thresher 1984; Kodric-Brown 1998). The combination of certain color patterns and display behaviors by adults may also convey information on their sexual identity and physiological state (Thresher and Moyer 1983).
The kelp bass, Paralabrax clathratus, is a temperate serranine fish that inhabits the nearshore, rocky-reef environments of southern California and northern coast of Baja California (Quast 1968; Miller and Lea 1972). Historically, the species has been an important component of local fisheries, which has led to a number of studies on various aspects of its biology (e.g. Quast 1968; Smith and Young 1966; Love et al. 1996). Histological evidence and sex-specific size frequency distributions of P. clathratus indicate a gonochoric sexual pattern, and no evidence of sex change has been reported (Smith and Young 1966; Oda et al. 1993). Recent studies by Erisman (2003) indicate that spawning occurs in single female, multi-male groups of 3 to 20 individuals within large breeding aggregations that form from late spring to early fall. Several hundred adults may aggregate in a small area during spawning. Spawning begins at sunset and occurs for several hours past dark. Unlike many tropical serranids, spawning in P. clathratus occurs continuously throughout the summer months and does not follow a lunar or semilunar rhythm (Erisman 2003).
The first scientific documentation of color changes in R clathratus appeared in Quast (1968), who noticed that some males became "golden on the snout" during the breeding season. This color pattern was most frequently observed in small males, although the color was present in some larger males. Similar results were reported by Turner et al. (1969). These early observations suggested that P. clathratus were seasonally dichromatic, although the descriptions were vague and no systematic investigations of the color patterns or their relation to the spawning season were ever conducted.
The purpose of the current investigation was three-fold: 1) to document and describe seasonal and ephemeral color patterns in P. clathratus, 2) to record and describe behaviors associated with specific color patterns, and 3) to compare the color patterns of collected individuals by sex and reproductive condition. This study represents the first complete description of color changes and related behaviors in a temperate serranine fish.
Materials and Methods Hook and Line Sampling
Eight hundred twenty-five individuals (365 males, 397 females, 63 juveniles) were collected by hook and line from May 2001 to April 2002 at several sites along the coast of Santa Catalina Island, California (33[degrees] 26' N, 118[degrees] 29' W) (Figure 1). In addition, 60 individuals were collected by hook and line in San Pedro, California on February 2002 (Figure 1). Collections were made on a monthly basis during the non-spawning season and daily during the spawning season. Standard length (SL) of each individual was recorded to the nearest mm and body weight was recorded to the nearest g. Time and date of collection and the lunar...
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