Although Caribbean mixed-species herbivorous fish groups are an important component to the reef community by helping to crop algae that often overgrow and kill corals, little is known of how they organize their foraging groups. In spite of a highly flexible membership, the basic structure of these groups consists of a “core species,” that leads the group and often is either the striped parrotfish (Scarus iserti) or the ocean surgeon (Acanthurus tractus). These species lead their groups to open areas where they feed largely on low profile turf algae. Other members prefer macro algae and are termed “associate species,” of which the two common species we studied were the stoplight parrotfish (Sparisoma viride) and the redband parrotfish (Sparisoma aurofrenatum). In spite of the large difference in group sizes between Jamaica and Grand Cayman Islands, the relationships between movement patterns and compositional changes were largely consistent. There was no support for the hypothesis that these dramatic and continuous group changes were related to foraging success. Instead, we speculated that these group changes perhaps were designed to maintain cohesion among a membership that was spread over a wide area. We also examined if associates species may be more than just passive followers of core species but rather instigated the attracting or the building of core groups. Both associate species do attract striped parrotfish in open areas and thus appear active in initiating mixed-species groups. Finally, given that associate species seem to derive little foraging benefit from following core species, we tested the hypothesis that associate species joined core groups to gain protection against predators. Associate species do not selectively join the larger groups of striped parrotfish but appear to join core species randomly and the groups they joined resembled the wide assortment of core groups available in the area. Thus, while associates may be joining core groups for protection, this protection was not based on sizes of core groups.

The decline in herbivorous fishes is an important contributing factor to the degradation of coral reefs, because their reduction contributes to macro algae overgrowth, which can have harmful effects on corals. Herbivorous fish often form mixed-species groups to locate foraging sites and for defense. The movements and compositions of these groups are dependent on the relative numbers of different species present. Some species, such as the striped parrotfish (Scarus iserti) and ocean surgeonfish (Acanthurus bahianus), serve as core species that lead mixed-species groups. Others, such as the redband (Sparisoma aurofrenatum) and stoplight parrotfishes (Sparisoma viride), follow core species as their associates. Despite the potential importance and abundance of mixed-species groups on reefs, little attention has been given to their composition and movements. Our intent was to determine whether the social dynamics of mixed-species groups in Jamaica were similar to those of Grand Cayman. The overall sizes of mixed-species groups were smaller in Grand Cayman. Focal striped parrotfish in Grand Cayman formed smaller groups, changed composition less, and moved less frequently than in Jamaica. Although probably more abundant than striped parrotfish, the ocean surgeonfish in Grand Cayman did not function as a core species but rather attached themselves as associates to the smaller striped parrotfish groups. Redband parrotfish moved less often in Grand Cayman, and appeared to be more dependent on striped parrotfish groups than stoplight parrotfish. While previous studies on herbivorous reef fish have shown that changes in foraging patterns can change with location, perhaps related to structural heterogeneity and resource distribution, this study illustrates that social interactions between common members of mixed-species groups also change. We suggest that the intra and interspecific social interactions in Grand Cayman are less attuned to finding erratically located high quality resources than those in Jamaica. Other plausible explanations are also considered.

The Convict Cichlid, Amatitlania nigrofasciata, is a popular model organism for behavioral ecologists to study mate choice, monogamy, and parental care. This freshwater Central American fish displays the rare phenotype of reverse sexual dichromatism, and despite the species' pervasiveness in behavioral laboratories, the role of female ornamentation in this system is uncertain. To better understand the function of female ornamentation, this study characterizes the visual sensitivity of A. nigrofasciata with particular attention to the long wavelength spectral sensitivity needed to perceive female coloration. We find Convict Cichlids to express a trichromatic complement of opsin proteins: SWS2A, SWS2B, and LWS. After confirming the expression of a LWS opsin gene, we inspected the LWS gene in order to speculate on directional selection potentially resulting in heightened sensitivity to female ornamentation. We examined seven tuning residues in the coding sequence of the LW'S opsin gene of A. nigrofasciata and present sequence data that suggest Convict Cichlids have heightened long wavelength sensitivity that is tuned to the female ornament present.

Aggression is often a crucial component to interference interspecific competition and yet there are few studies that examine fight behavior when the opponents are different species. To examine conspecific and heterospecific aggression, we used two species of Caribbean damselfish, the dusky (Stegastes adustus) and the longfin (S. diencaeous) with each one serving as the heterospecific opponent to the other species. Our study was confined to whether or not each species measures the body length of the other species as if it were a conspecific intruder. Body length plays an important role in fight outcome in many species of fish and we presumed that both the dusky and the longfin would use it when assessing opponents. Both the dusky and the longfin damselfish were then presented with two individuals that were either greatly different or minimally different in size. When presented with individuals that differed greatly in size, both species spent more time attacking the larger individual, irrespective of species. However, when the size difference was small, the focal dusky and the longfin responded differently; the dusky showed no preference in either conspecific or heterospecific pairs while the longfin continued to show a bias toward the slightly larger individual. Thus, while we were surprised by the species differences, both the dusky and the longfin were internally consistent in how they treated conspecific and heterospecific opponents.

Interspecific aggression may be caused by competition for resources or result from species misidentification. Species may exhibit aggressive responses that are similar, or symmetrical, to each other, or one species may respond more aggressively than the other, exhibiting asymmetrical aggression. We examined aggressive symmetry in two territorial Caribbean damselfish species, the longfin damselfish (Stegastes diencaeous) and the dusky damselfish (S. adustus) because they exhibit qualities that make such relationships hard to predict. These two species show considerable habitat overlap, are closely related and are nearly identical in gross morphology, suggesting they would show the same intensity of aggressiveness to heterospecifics and conspecifics. However, longfins reach a larger adult size, which may cause these two species to instead aggress asymmetrically toward one another. We also tested residents' responses toward bluehead wrasse (Thalassoma bifasciatum), a common egg predator, to see if highly similar species respond similarly to a presumably equal threat not likely to be misidentified as a conspecific. We presented residents with either a single intruder or two simultaneous intruders to determine if context affected aggressive behavior. When presented with a single intruder, both resident species attacked conspecifics and congenerics with somewhat similar aggression, suggesting either a broad competitive overlap or misidentification. When residents were forced to divide their time between two simultaneous damselfish intruders, they clearly aggressed more intensely toward conspecifics. Additionally, longfins were more aggressive to bluehead wrasse than were dusky damselfish in single and paired presentations. We propose that the higher aggression toward wrasse by longfins is related to longfins having territories on which their eggs are naturally more exposed compared to a typical dusky territory in which eggs are more hidden.

Caribbean damselfish species (genus Stegastes) are permanently territorial, display obvious aggressive behavior related to territory defense, and have divergent habitat preferences for primary territory substrates. Territory quality is directly tied to variation in reproductive success among individuals, which suggests that ecological isolation plays a key role in the maintenance of species boundaries in this genus. If so, hybridization is expected to occur among closely-related damselfish species when there is a limitation in the availability of preferred primary habitat. To test this prediction, we collected damselfish from both high disturbance (Jamaica) and low disturbance (Barbados) coral reef environments, and looked for evidence of hybridization among species based on both morphological variation and discordance between mitochondrial and nuclear genetic markers. Consistent with the hypothesis that species boundaries in this system are maintained by strong substrate preferences and aggressive territoriality, we found evidence for extensive hybridization in Jamaica, where intense hurricanes have led to considerable habitat degradation over the last 30years. In light of ongoing climate change, this result suggests that hybridization leading to a blurring of ecological species boundaries may represent an increasingly common yet underappreciated threat to many coral reef fish species.

There is a trade-off between mutually incompatible behaviors involved in conspecific aggression and courtship by territorial male beaugregory damselfish (Stegastes leucostictus). This trade-off may be variable based on the proximity of each stimulus. We first tested whether presenting male and female conspecific stimuli at varying distances from the breeding site influenced the territorial male's behavioral response by placing a single female or a single male in a clear plastic bottle 1m or 2m from the breeding site of the focal male. We found that the focal males responded similarly to females at either distance while they decreased their response to males at the greater distance. To test how distance influences the trade-off between inter- and intrasexually selected behaviors, we simultaneously placed bottled males and females near a male's breeding site. Reducing the proximity of one stimulus resulted in an increased response to the other stimulus. We suggest that the trade-off between behaviors is variable and show that distance plays a role in territorial males' behavioral response to multiple conspecific stimuli.

We studied the prevalence of black-band disease (BBD) and white plague type II (WP) in two sites (Frederiksted and Butler Bay) within a St. Croix coral community that varied in relative exposure to sewage outflow. During sewage discharge events, fecal coliform and Enterococci data indicated impact area was limited to Frederiksted. We gathered data from seven belt transects in each of the two sites during the summer of 2001. We sampled 1046 colonies in 343 m 2 in Frederiksted and 2399 colonies in 302 m 2 in Butler Bay. There was significantly (Chi-square: df = 1, p = 0.0001) more disease in the impacted site with 13.6% of colonies of locally susceptible species infected (n = 566) versus the up current site that had 3.7% (n = 1344). Prevalence was highest for Diploria clivosa, with 23.7% of total colonies (n = 76) infected in the sewage impact site, which was significantly (Chi-square: df = 1, p = 0.0001) more than in the Butler Bay site where only 2.5% of the total colonies (n = 320) were infected. Recorded mortality, due to WP type II, was most severe for Dichocoenia stokesi with 26% of the infected colonies (n = 38) dying in just two months or 9.4% of the total D. stokesi sample population (n = 107). The results of the study suggest a relationship between a high prevalence of BBD and WP type II and exposure to sewage.

Body size is an essential variable in many behavioural and physiological studies. Previous methods for body size estimation present two conflicting drawbacks. They either (1) consider variation in only one dimension through linear measurements or (2) they are time and resource consuming, hard to apply in field conditions and/or stressful to the animal. We present a method for estimating body size, an ellipsoid approximation, which requires simple linear measurements and incorporates variation in three dimensions. The method is tested on two species of teleost fish and one species of insect. The amount of variance in mass explained by the proposed method exceeds that of previous reported methods, including the most accurate ones, that usually require expensive digitising procedures and/or stressful handling.

In this experiment we examined the roles of male size and female eavesdropping in divorce using the serially monogamous convict cichlid (Archocentrus nigrofasciatus) by testing predictions based upon the better option hypothesis of divorce. We tested the role of male size by exposing females to males that were 20-25% larger than their current mate or males that were similar size to their current mate. Female convict cichlids prefer larger males, therefore we predicted that the frequency of divorce would be higher when the alternate mate was larger than the current mate. We also examined the role of eavesdropping as a mechanism of female assessment of relative male quality. Females were either permitted to eavesdrop (males physically interacted) or females were unable to eavesdrop (males prevented from interacting). We predicted that female eavesdropping would result in greater frequency of divorce. We found that females chose divorce most often (50% ending in divorce) in the treatment where the alternate male was larger than the current mate and eavesdropping was permitted, whereas females never chose divorce in the treatment where the alternate male was similar in size to the current mate and the female was not permitted to eavesdrop. Although it had a mild effect, male size difference alone did not significantly increase divorce. When size difference was coupled with eavesdropping, however, females did significantly increase their divorce rates.

Selection usually acts differently on males and females during intrasexual competition for resources and/or mates. Nevertheless, agonistic behavior has been examined both theoretically and empirically mostly in males. Our research questions whether males and females follow the same rules of engagement in intrasexual contests as predicted by the sequential assessment model (SAM). The SAM predicts negative correlations between contest intensity and duration and the magnitude of asymmetry in resource holding power (RHP) between the contestants, such that the most escalated contests are those between similarly endowed individuals. We staged male and female intrasexual contests with varying degrees of body size asymmetry under a round robin design using the monogamous Texas cichlid fish (Herichthys cyanoguttatum) as a study case. We used Mantel's matrix analysis to compare how the behavioral content, duration, structure, and outcome of male and female contests were affected by the relative body size of the contestants. In the case of males, relative size in each contest predicted outcome, duration, and frequency of conventional and escalated behaviors according to prevailing theory. Female contest structure and outcome, however, were not predicted by the relative size of contestants. We discuss our results in terms of other asymmetries that might be important in structuring female contests, and we propose potential approaches to study female-female aggression.

Using the permanently territorial beaugregory damselfish (Stegastes leucostictus), we examined behavioral differences between neighbors and how they relate to territory quality, male size, and social interactions. We manipulated territory quality by replacing some male's poor quality natural breeding sites with artificial sites. These artificial sites were known to rapidly increase a male's reproductive success. Three types of paired neighbors were tested: both males with high quality artificial sites (Group I); both neighbors with low quality natural sites (Group II); one male with a low quality natural site and his neighbor with a high quality artificial site (Group III). Because neighbors rarely interact, we stimulated interactions by placing a bottled male or a bottled female midway between the two breeding sites. The area between the 2 sites was rarely patrolled by either neighbor and we judged them to be outside of either male's territory. Although we found that both neighbors were in close proximity to each other while they simultaneously attacked a bottled male or courted a bottled female, the neighbors rarely interacted. Without one neighbor aggressively dominating the other neighbor, the neighbor that attacked or courted the bottled animal most intensively was termed 'dominant.' For pairs where both neighbors defended sites of similar quality (Group I and II), dominance was not related to male size. Reproductive success was only measured for Group I (both males with artificial sites) and relative reproductive success was not related to dominance. For heterogeneous pairs (Group III), dominance was related to territory quality (the male given the artificial site was always dominant when compared to his neighbor) but not male size. Irrespective of pair type (Groups I, II, or III), there was no inter-group differences in behavior among the dominants or among the subordinates. With the removal of the dominant individual, the remaining subordinates increased their aggressiveness toward bottled males and resembled the dominant individuals that were removed. Removing subordinate individuals caused no change in the behavior of remaining dominant individuals. Thus, the dominant males of all group types appeared to suppress the behavior of subordinates. We speculate that when neighbors have similar sites (Groups I and II), their past social interactions may be responsible for the development of the initial dominant-subordinate relationship. However, this dominant-subordinate relationship can be reversed by giving the subordinate male a higher quality breeding site (i.e. Group III). We found no evidence that a subordinate's reproductive success was influenced by his more dominant neighbor and we speculate that it may influence his ability to secure a breeding site.

Research on fighting has emphasized contests between individuals, typically males, but pairs also compete. Monogamous pairs of convict cichlids (Archocentrus nigrofasciatum) compete with other pairs for breeding sites in nature. We simulated such contests with competing pairs who differed in one or two of three possible asymmetries: body size, residency, and pair experience. In single-asymmetry experiments, larger pairs defeated smaller pairs, resident pairs defeated intruder pairs, and experienced pairs (those that had been together for 96 hours) defeated novice pairs (those that had been together for 48 hours). Thus, each of the three asymmetries was important in determining the outcome of contests. In further experiments, pairs had two contrasting asymmetries simultaneously. Larger pairs always defeated smaller pairs (15-25% difference in male standard length) even though the larger pair was inferior in one of the other asymmetries. When the two pairs were similar in size (standard length of males differed less than 6%), experienced intruder pairs defeated novice resident pairs nearly half the time. This is the first study to investigate the effects of pair experience on fighting ability. Although we predicted that experience might benefit pairs through improved coordination of their behaviour, behavioral measures such as time spent at the spawning site and pair digging behaviour showed no significant differences among groups. We posit that more experienced pairs fought harder for the breeding site because they were closer to spawning and the expected payoff for winning the breeding site was therefore higher. Finally, when both pairs were of similar size but differed in residence status and experience, there was more escalated fighting than in contests between size-disparate pairs; two possible interpretations of this result are discussed.

In Jamaica, the saddle blenny (Malacoctenus triangulatus) and the beaugregory damselfish (Stegastes leucostictus) defend territories in small rubble and sand habitats. When defending separate territories, both species were highly aggressive to conspecifics and both attacked the egg-eating bluehead wrasse (Thalassoma bifasciatum). When defending the same territorial space, both species remained highly aggressive to conspecifics. However, in this association, the beaugregory was the primary defender against the bluehead wrasse.

Naked gobies (Gobiosoma bosci) are a "scaleless" species of gobies. Males of this species form breeding aggregations and establish individual breeding territories within these aggregations. A male will defend a shell, entice females to spawn in it, and care for the eggs until they hatch. Experiments were conducted using 5 gallon aquariums, fine sand substrate, and ½" PVC tubing for habitat. Pairs of fish were chosen based on closeness of size. Competitions were filmed so that behaviors could be assessed more accurately at a later time. Three hypotheses were considered. (1) With increasing size difference there will be a decrease in escalated behaviors. (2) With increasing size difference there will be an increase in conventional behaviors. (3) With increasing size difference there will be a decrease in fight duration. A total of 11 behaviors, both conventional and escalated, were observed and counted. Conventional behaviors were trembling, bouncing, head raising, and chasing. Escalated behaviors included flitting, charging, and biting. Running away, time spent in the tube, time spent near the tube, and breeding activity were also counted behaviors, but they were classified as neither conventional nor escalated. Data were analyzed using linear trendlines in an XY scatter plot with size difference as the independent variable. Hypotheses 1 and 3 were shown in this study; however, hypothesis 2 was not supported. Bar graphs showing rates per minute of all behaviors were also constructed. Results are discussed on the basis of game theory (Maynard Smith & Parker, 1976), assessor strategy (Maynard Smith, 1982), and the sequential assessment game (Enquist & Leimar, 1983; Keeley & Grant, 1993; Koops & Grant, 1993).