Agonistic behaviour of age 0, age 1 and non-breeding adult Arctic grayling Thymallus arcticus (Pallas)

Age 0 Arctic grayling begin to show agonistic behaviour 3 weeks after emergence and are territorial by their fourth week. Age 1 fish are territorial throughout the summer feeding period. In adults, territoriality is restricted to larger males during the early spring breeding season while after the breeding season both smaller adult males and adult females also hold territories.
In sub-adults, larger fish and resident fish tend to win most fights. In adults, males usually win against females. In fights between adults of the same sex, larger and resident fish usually win.
The lateral display becomes more important in the agonistic repertoire of Arctic grayling as they mature and the characteristic large dorsal fin develops. Arctic grayling appear to lack an appeasement display.     

Field observations of the spawning behaviour of European grayling

During observations of the River Ourthe, Belgium, 70 spawning attempts were recorded during the reproductive period of the European grayling. Thirty-six per cent of the spawning attempts proceeded to completion, while interference by another male may explain some of the incomplete acts. Sneaking behaviour was observed and one spawning act included two males and one female.     

The behaviour of Abudefduf zonatus (Pisces,pomacentridae) at Heron Island,Great Barrier Reef

Social organization and reproductive behaviour of Abudefduf zonatus were studied at Heron Island, Great Barrier Reef. This species is closely associated with the sand and coral substrate of the inner reef flat zone. Territorial, clustering, nest-digging, breeding and parental care behaviours are described. Mature males maintain territories for several weeks or longer around empty clam shells in which periodic spawning occurs. Females and sub-adult males hold territories interspersed among those of adult males. No pair bonds are formed, and eggs are guarded only by males. Breeding is roughly synchronized among fish of one area. Clustering behaviour may contribute to breeding syndrony in local populations.     

The social and mating system of the maternal mouthbrooderTropheus moorii (Cichlidae) in Lake Tanganyika

Territorial behaviour, reproduction and migration of the epilithic algal eater,Tropheus moorii, were investigated in Lake Tanganyika, Africa. Adults of both sexes had individual feeding territories which adjointed each other. Males, who occupied higher rocks than females, usually stayed at the same sites for more than 5 months. Females left their territories to pair with males in the males’ territories. Paired females actively foraged under the protection of their mates for up to 3 weeks prior to spawning. After spawning, females usually settled in a site unoccupied by territory-holders to mouthbrood the offspring for a month. An examination of the ovaries and a removal experiment of dominant males suggest that females cannot attain fully mature ovaries in their own territories and choose males whose territories can provide enough food to satisfy their nutritive demand. The evolution of a number of local colour morphs in this fish is briefly discussed in relation to social selection.     

A preliminary report on the spawning behaviour and nature of sexual selection in the barbel, Barbus barbus (L.)

In the spring of 1974 the migration and spawning behaviour of barbel, Barbus barbus (L.) were observed. The migration and behaviour of males prior to the spawning attempts may be strategies designed to increase the quota of receptive females experienced by each male. Spawning attempts were divided into two categories: successful and failed. Successful attempts comprised six sequential sub-events: approach period, pre-spawning phase, spawning, post-spawning phase, dispersal period and inter-spawning period. The spawning and post-spawning phases did not occur in a failed attempt. The success or failure of attempts was dependent upon the number of males present. The advantage gained by females abandoning attempts when the male densities were high is discussed. In both the pre-spawning phase of failed attempts and the post-spawning phase of successful attempts, males attempted to drive away other male competitors by the use of male 'chase away' interactions.     

Alternative male mating tactics of the endemic Red Sea parrotfish Scarus ferrugineus

The present study shows that small non‐territorial terminal‐phase males of the rusty parrotfish Scarus ferrugineus are reproductively active and are comparable with initial‐phase males in behaviour, rates of participation during group‐spawning and success in streaking into pair spawning. Large territorial terminal‐phase males defend contiguous territories for several hours during the morning where they pair spawn with initial‐phase females.     

Reproductive success in male Japanese minnows,Pseudorasbora parva: observations under experimental conditions

To evaluate the spawning success of male Japanese minnows,Pseudorasbora parva, and female mate choice, spawning behaviour was observed under both artificial and experimental conditions. Larger males had larger territories and greater reproductive success. The body weight of territorial males decreased during the maintenance of territories, while that of non-territorial males increased significantly. When the weight of non-territorial males exceeded that of territorial males, the former began to establish new territories on the substrate, suggesting a conditional strategy by non-territorial males to trade off immediate reproductive success with growth and hence improve future reproductive success. Females chose males with larger body size, probably based on dominance rank rather than the quality (or size) of territory. It was concluded that females choose males of higher dominance rank and that males compete for large territories, both of which play an important part in male reproductive success.     

Female Mate Preference for Males Having Long and Symmetric Fins in the Bower-holding Cichlid Cyathopharynx furcifer

Female mate preference in a bower-holding cichlid, Cyathopharynx furcifer, was studied in Lake Tanganyika. Most males held territories with crater-shaped bowers in sand, but some males held territories without bowers. Territories were distributed adjacently and females visited them to spawn. After engaging in circling behaviour with the male, a female deposited eggs in the bower. Soon after spawning, the female picked the eggs up into her mouth and brooded them in places away from male territories. Female mate choice appeared to follow three steps: 1) females visited only bower-holding male territories, and more frequently visited territories of males that performed courtship displays at a higher frequency and had longer pelvic fins; 2) females preferred to start circling with males having longer and more symmetrical pelvic fins; 3) females chose males with more symmetrical pelvic fins as their mates. Less than 7% of females that visited male territories spawned eggs in the bowers. In contrast to other bower-holding species, bower size did not correlate with male reproductive success in C. furcifer. Bowers may therefore be essential as spawning sites or may function as a species recognition character for females. Female choice may be dependent instead on males having long and symmetrical pelvic fins apparent during the circling behaviour carried out in the bowers.     

Predation risk and the opportunity for female mate choice in a coral reef fish

The influence of predation risk on the opportunity for female mate choice was investigated in the tailspot wrasse Halichoeres melanurus at two sites on a coral reef in Okinawa, Japan. Females mated repeatedly with the nearest males, but they also changed mates frequently at both sites. Mate changes were seen not only in the context of spatiosocial changes (mate disappearance or shifts in male territories) but were also probably the result of actual mate choice by females. Females at one site (site A) changed mates more often and conducted longer spawning trips from their home ranges to male territories than at the other site (site B). Fish at site A were faced with a higher frequency of predators than that of site B. However, fish of site A suffered fewer attacks from predators because they had more shelter, suggesting lower predation risk in that site. These results suggest that females under higher predation risk had less opportunity to choose preferable mates and that they had to mate with the same, nearest males in most cases.     

Multiple matings in the blue gourami, Trichogaster trichopterus (Pisces,Belontiidae)

The reproductive behaviour of the blue gourami, Trichogaster trichopterus, was examined in 15 bisexual pairs and 22 trios maintained in 75-litre aquaria for 23 days. During this time, 74 spawning episodes occurred among 26 different pairs and trios. Sixty-nine of these spawnings were directly observed. Both males and females were capable of mating repeatedly with the same or different partners with as little as 20 to 24 h separating successive spawnings. Females often mated with two males in the same afternoon, while only one male succeeded in mating with two females in one day. It is concluded that blue gouramis probably do not form pair bonds and that both sexes will mate with differet partners when the physical environment permits two or more males to maintain territories in the same aquarium.     

Females prefer mating males in the carmine triplefin,Axoclinus carminalis,a paternal brood-guarder

Synopsis This study investigates the role of male mating status in female choice patterns in the carmine triplefin, Axoclinus carminalis, a tripterygiid fish that exhibits paternal care. The distribution of daily reproductive activity is clumped, with many males receiving no mates and some receiving three or more. Females in this species do not prefer larger males, and characteristics of the oviposition site appear to have minimal effects on male mating success. When a female is removed from a male early in the daily spawning period, that male attracts fewer additional females for the remainder of the spawning period than does a control male. These changes in mating success are temporary, and do not affect mating success on subsequent days. A preference for mating males or males that are guarding eggs could provide asymmetric benefits for males to defend oviposition sites. This preference for males with eggs could be acting alone or with other factors such as high variance in oviposition site quality to favor the evolution of paternal care in fishes.     

Territorial and non-territorial spawning behaviour in the bream

The spawning behaviour of bream Abramis brama was studied in 1993, in a harbour on the River Meuse, Belgium. Fish spawned from 22 to 27 April and from 11 to 14 May, when the water temperature rose to 14.5) C. The reproductive behaviour of the bream was studied within a 15 m long part of the harbour using a video camera. Territorial males with tubercles (33–43 cm total length; >5 years old) defended bank areas of diameter 80–150 cm which included spawning substratum, i.e. roots of alder and willow trees and aquatic plants. Water depth ranged from 25 to 50 cm. Non-territorial males without tubercles (24–33 cm; 3–4 years old), remained 2–4 m away from the bank. Aggressive behaviour between males was frequent and, occasionally, males with tubercles were unable to defend a territory. Mature females (25–43 cm; >3 years old), coming from the deeper water of the surrounding area, were followed by non-territorial males before spawning in territories near the bank.     

Diurnal periodicity of spawning activity of permanently territorial damselfishes (Teleostei: Pomacentridae)

Synopsis Like other congeneric damselfishes, the herbivorous Stegastes altus defends individual feeding territories from heterospecific food competitors, regardless of sex. Females spawned demersal eggs for 31.4 min (n = 25) at the nest in territories of males 0–75 m away from theirs. Throughout the spawning season (June to September), spawning occurred only at dawn, mainly just after sunrise. Daily activity of the fish community showed that potential diurnal food competitors were few or inactive only at dawn and dusk. The frequency of intrusions into the female's territory by heterospecific competitors were as low when she left her territory to spawn at dawn, as they were in the daytime when she defended it. Removal of the female in the daytime resulted in a significant increase in intrusion frequency. An ‘anti-competitor hypothesis’, whereby dawn spawning ensures the food resource in the female's territory seems to explain not only the spawning periodicity in S. altus but also the timing of spawning of other permanently territorial damselfishes. Contribution from the Laboratory of Animal Ecology, Kyoto University, No. 492.     

Social factors of group spawning as an alternative mating tactic in the territorial males of the threespot wrasse <Emphasis Type="BoldItalic">Halichoeres trimaculatus</Emphasis>

In most labrid fishes, large males with bright terminal phase (TP) coloration normally defend mating territories and pair spawn after following (i.e., courting) solitary females. It has also been reported that the TP males may abandon their territories and participate in group spawning when mating groups of small non-territorial males with drab initial phase (IP) coloration frequently intrude into the territories of TP males. In the similar situation of the present study, however, the territorial TP males of the threespot wrasse, Halichoeres trimaculatus, did not always participate in group spawning but continued pair spawning. Only the TP males that had few opportunities to encounter solitary IP individuals participated in group spawning, frequently following the mating groups of IP individuals. It is therefore suggested that group spawning of the territorial TP males is regarded as a tactic of making the best of the bad situation by the TP males with few opportunities to pair spawn in an area where group spawning dominates.     

Environmental determinants of butterflyfish social systems

Synopsis Butterflyfishes (Chaetodontidae) display a variety of social systems, including monogamous pair-bonds, harems, and schooling with group spawning. The range of reproductive options available to butterflyfishes is shaped by their general life history characteristics, such as broadcast spawning with widely dispersed pelagic larvae, large body size and low adult mortality. The distribution and quality of food resources are major determinants of group size and mobility, thereby influencing the relative costs and benefits of available options, and determining specific social systems. Planktivorous and corallivorous butterflyfishes exemplify the relationship between food resources and social systems. Pelagic plankton is a patchy, but temporally and spatially unpredictable food resource which is efficiently exploited by fish in mobile schools. Neither sex is able to monopolize food resources necessary for the other sex, and plantivorous butterflyfishes appear constrained to spawn in groups. In contrast, corals are stable and predictable in space and time, favoring residence in one area and territorial defense of that space by coral-feeding butterflyfishes. Females defend food resources from other females, and males defend territories containing a female from other males. Males attempt to defend areas containing more than one female, but are unsuccessful. A monogamous social system results. This system favors the evolution of cooperative behavior between mates to increase female fecundity, as long as the male has an opportunity of sharing in that reproduction. Mate removal experiments conducted on two monogamous coral-feeding species,Chaetodon multicinctus andChaetodon quadrimaculatus reveal a division of labor between male and female pair-mates. Paired males assume most of the territorial defense activities, allowing their mates to feed more.     

Male spawning success and female choice in the mottled triplefin,Forsterygion varium (Pisces: Tripterygiidae)

A detailed analysis was made of the variation in spawning success among male Forsterygion (э Tripterygion) varium. The aim was to assess whether females were mating selectively and, if so, to examine the basis of that choice. Eggs were laid on small rocks within the males' territories. Females did not distribute eggs randomly among males. Some males guarded as many as 23000 eggs in one breeding season, while others experienced little or no breeding success. Male spawning success was positively correlated with both their size and some characteristics of their territories, namely the amount of spawning substratum and the presence of a large boulder adjacent to the territory. Experimental manipulations indicated that female choice of males was based on these features. Addition of small rocks into the territories of previously unsuccessful males resulted in a significant increase in spawning success. Conversely, spawning success of the most successful males decreased when small rocks were removed from their territories. When successful males were removed, each territory was occupied by small males; however, there was no significant change in the spawning success of these males. This experiment suggested that, although territory quality was important, female mating decisions could also be influenced by male characteristics such as body size.     

Courtship displays and coloration as indicators of safety rather than of male quality : the safety assurance hyposthesis

Male courtship displays and bright coloration are usually assumedto provide information to females about some aspect of themale's value as a mate. However, in some species, courtshipmay serve another function—namely, indicating the currentpredation risk at the mating site and assuring the female thatit is safe to mate there at this time. We developed this safetyassurance hypothesis (SAH) and tested its predictions in thebluehead wrasse (Thalassoma bifasciatum), a Caribbean reef fish. Females in this species come to males' territories to spawn,and males court each arriving female. Males with larger whiteflank patches court less intensely than less bright males.We show that such males are probably more visible to predatorsand thus need not court so intensely to provide the same degreeof safety assurance to a female. When model lizardfish predatorsare presented at spawning sites, males habituate to them quickly,but newly arriving females who see the predator are expectedto demand more assurance of site safety. Accordingly, and consistentwith the SAH, males court females more intensely (longer averagecourtship bout length) under such circumstances, but maleswith bright flank patches do not increase their courtship asmuch as duller males do. Despite this relatively low intensityof courtship, the spawning rate of bright males does not declinerelative to that of duller males in the presence of a predator,suggesting that bright coloration conveys a differential benefit.Females of species like the bluehead wrasse, who spawn repeatedlyover the course of their life, are expected to be more concernedwith their own risk of mortality during each spawning boutthan with the quality of a particular male. It is in such speciesthat we expect the SAH to be most applicable.     

Androgen control of social status in males of a wild population of stoplight parrotfish, Sparisoma viride (Scaridae)

In the protogynous stoplight parrotfish (Sparisoma viride), large males defend territories that encompass the home-ranges of several mature females. However, high-quality habitat is in short supply, such that smaller, competitively inferior males do not defend territories. We investigated the role of 11-ketotestosterone (11KT) and testosterone (T) in the regulation of territorial behavior in a wild population of a protogynous reef fish, the stoplight parrotfish, at Glover's Reef, Belize. Radioimmunoassay of plasma samples from individuals of known social status revealed that nonterritorial males have lower levels of T and 11KT than territorial males. Nonterritorial males allowed access to vacant territories underwent pronounced increases in T and 11KT. When sampled 1 week after territory acquisition, levels of T and 11KT in new territorial males were significantly higher than the levels in established territorial males, but by 3 weeks after territory acquisition, there was no significant difference. We further investigated the hypothesis that such short-term increases in androgen levels are a response to intense male-male interactions during territory establishment. Simulated territorial intrusion promoted increased plasma levels of both T and 11KT while access to vacant territories without neighboring territorial males did not. These findings suggest that the endocrine system plays a role in fine-tuning the levels of territorial aggression exhibited by male stoplight parrotfish. We discuss these results in light of recent theory in behavioral endocrinology.     

Mating patterns of female Leon Springs pupfish Cyprinodon bovinus

In a field study of Leon Springs pupfish Cyprinodon bovinus, two questions about female promiscuity were investigated. First, were females selective in the males with whom they spawned or were they unselective, spawning randomly among males? Second, how promiscuous were the females, i.e. with how many males did they spawn? If simply spawning with many males maximized a female's reproductive success, then females might be expected to spawn randomly with as many males as possible. Alternatively, if females were selective but engaged in multiple mating, they would limit their spawning to preferred males. In the only wild population of this endangered fish, breeding males defend closely associated territories in the shallow margins of a single desert pool. No territories were observed elsewhere in the pool. Therefore, all territorial males were present simultaneously and females could survey all of them, depositing any number of eggs with one, a few or many males. Rather than spawning randomly, females surveyed many males first, visited relatively few males and ultimately spawned with a small fraction of those available males. With increasing numbers of spawns, however, females increased the number of different mates with whom they spawned. Thus, females showed a bet‐hedging tactic of having a narrow mate preference while also laying eggs in the territories of other males, possibly to reduce egg predation and to avoid inbreeding.     

The trophic interactions of young Arctic grayling (Thymallus arcticus) in an Arctic tundra stream

1. Young (0+) Arctic grayling (Thymallus arcticus) have the potential to control the trophic structure of Arctic tundra streams through consumption, nutrient excretion and the modification of prey behaviour. The effect of young grayling on three trophic levels (algae, invertebrates and fish) was investigated by manipulating fish density and by fertilizing the river with phosphorus (P). 2. Nutrients, epilithic chlorophyll a, benthic invertebrates and fish biomass were measured within each fish density treatment (0, 4, and 40 fish m^–2) within the P-limited reference zone and the P-enriched fertilized zone of the Kuparuk River, Alaska. 3. Epilithic chlorophyll a increased with increased fish density in both reference and fertilized zones, while mayfly density decreased with increased fish density in the fertilized zone only. Final mean mass of young grayling in the 40 fish m^–2 cages was lower than mean mass in the 4 fish m^–2 cages. 4. Young grayling may produce a top-down cascading trophic effect in areas where nutrients are not limited. 5. River nutrient status and river discharge may modify the strength of top-down control by young grayling.