Implications of life-history strategies for a new wrasse fishery

The variety of life-history patterns exhibited by the five species of wrasse common in Northern Europe are reviewed. The two larger wrasse species, the ballan, Labrus bergylta Ascanius, and cuckoo, Labrus mixtus (L.), are exploited through sport angling. The three smaller species, the corkwing, Symphodus (Crenilabrus) melops (L.), rock cook, Centrolabrus exoletus (L.) and goldsinny, Ctenolabrus rupestris (L.), are being exploited by a new fishery for use as parasite cleaners of farmed salmon.
The nature of salmon farming limits the wrasse fishery to a minimum size, restricted areas and the warmer months of the year. The fishery may be expected to alter population structure through selective removal of larger fish. Removal of dominant territorial males may affect social structures and removal of nest-guarding males would reduce egg survival. Quantitative models incorporating stock size and fishery requirements are now required.     

The effect of territorial damselfish (family Pomacentridae) on the space use and behaviour of the coral reef fish, Halichoeres bivittatus (Bloch, 1791) (family Labridae)

Most demersal species of damselfish (family Pomacentridae) are territorial herbivores that aggressively chase other fishes away from their nests. This study investigates whether the aggressive territorial damselfish, Stegastes leucostictus, modifies behaviours and home range area use in a less aggressive, non-territorial species, the slippery dick wrasse, Halichoeres bivittatus (family Labridae). Damselfishes and wrasses are ubiquitous and abundant members of coral reef fish assemblages around the world; hence, this study has broader implications beyond the two Caribbean species chosen for this study. A manipulative field experiment consisted of transplanting one or three S. leucostictus into artificial shelters positioned within adult or adjacent to juvenile H. bivittatus home ranges. The introduction of damselfish had little effect on the size of home range areas of juvenile or adult wrasses, but had a significant effect on the location of their home ranges. The damselfish also affected adult microhabitat use but did not affect use by juveniles. In addition, there was an increase in damselfish-wrasse interactions that resulted in a significant reduction in the amount of time adult wrasses could spend foraging or in a foraging assemblage. It was concluded that aggressive interactions with territorial damselfish affect individual H. bivittatus space use and may consequently affect the spatial distribution of H. bivittatus populations.     

Preliminary study on female choice of mates versus sites in a wrasse, Cirrhilabrus temminckii

Female choice of mates versus sites was studied in a wrasse, Cirrhilabrus temminckii. Males had territories within a restricted area on a rocky slope at which females visited and pair-spawned pelagic gametes. Females visited several males or territories before spawning, suggesting the opportunity of female choice. Of the four characteristics of territorial males examined—body size, ratio of pelvic fin length to body size, courtship, frequency and territory depth—only territory depth was significantly correlated with daily mating success of males. The former three male characters were not related to territory depth. These results suggest that female C. temminckii chooses deep sites rather than specific mates in mating.     

Intraspecific variation in sand-diving and predator avoidance behavior of green razorfish,Xyrichtys splendens (Pisces,Labridae): effect on courtship and mating success

Synopsis Green razorfish are Caribbean wrasses that live in harems on shallow sand or seagrass beds, which offer little cover for predator avoidance (PA). Field observations showed that non-conspecific fishes that intruded were either attacked, ignored, or actively avoided. Food competitors and small piscivores were attacked by male razorfish. Razorfish PA behaviors varied among three habitats with different substratum compositions, suggesting that these fish possess phenotypic plasticity for PA behavior. In a rocky-rubble habitat, razorfish dove into the coarse sand for PA, but most sand dives observed there were to soften a small site for future PA. In a sandbed habitat, they hid among coral branches and dove into the sand when attacked; few maintenance dives were observed as soft sand was widespread. In a seagrass habitat, they hid among blades of grass for PA, and dove into the sand less frequently than at the other sites. Some female razorfish that were transferred among habitats adopted PA behaviors similar to those of females in the new site, while others did not, suggesting that behavioral plasticity is not universal in this species. Razorfish spawned lower in the water column in the presence of natural predators and a predator model, than when these were absent. When the predator model was introduced into a male's territory during spawning periods, there was a reduction in his courtship rate, but not in the number of spawns he achieved. Predation pressure may reduce males' long-term fitness by causing decreased courtship rates which can facilitate sex change in harem females.     

Social control of terminal phase transition in primary males of the diandric wrasse, <Emphasis Type="Italic">Halichoeres poecilopterus</Emphasis> (Pisces: Labridae)

In many diandric fishes, large territorial males with bright body coloration (terminal phase (TP) males) are derived either from initial phase (IP) females that change sex to male or from IP primary males that change color and behavior, but do not change sex. The mechanism controlling the transition of IP primary males into TP males is not well understood. We conducted cohabitation experiments to examine social conditions favoring TP transition by primary males in the diandric wrasse, Halichoeres poecilopterus. IP primary males always started TP-specific sexual behavior in the presence of a smaller subordinate, and subsequently acquired TP body coloration. In contrast, primary males under subordinate conditions often performed female-like sexual behavior. In pairs with similar body sizes, both individuals initiated TP male behavior. The results suggest that TP transition in primary males may be closely related to a dominance relationship (or size order) within social groups, as it is in the case of sex change by females.     

颈斑尖猪鱼——中国南海隆头鱼科新纪录种

本文根据采自海南岛的标本描述了中国南海一新记录种:颈斑尖猪鱼(Leptojulis lambdastigma)。本种的主要形态特征为:体长形,体长为体高的3.7~4.0倍,为头长的3.1~3.6倍;头长为吻长的2.7~3.3倍,为胸鳍长的1.45~1.65倍;头裸露无鳞;两颌前端各具2对大犬齿,外侧1对犬齿弯向外后方;背鳍Ⅸ-12,臀鳍Ⅲ-12,胸鳍i(不分支)+11-12(分支);侧线完整,侧线鳞27;颈部具一个"V"形大黑斑,胸鳍后部的上方、侧线的下方具一小黑斑。新鲜标本头部具2条黄色纵带,沿体侧分别经眼和胸鳍基部向后达尾鳍基部;体侧背部具1条浅棕黄色条带;胸鳍基部棕红色,后部浅色;臀鳍浅蓝色;尾鳍下部淡蓝色,上部橙色。本种与尾斑尖猪鱼(L.urostigma)形态较为相似,主要差别在于颈斑尖猪鱼的颈部具有一显著的"V"形黑斑,尾鳍基部无黑斑(尾斑尖猪鱼具此黑斑)。     

中国隆头鱼科一新纪录种——雀尖嘴鱼

尖嘴鱼属(Gomphosus)是一群分布于印度洋和太平洋热带珊瑚礁海域鱼类,共有2种,以往在中国海域记录有1种杂色尖嘴鱼(G.varius)。我们在分析20世纪90年代采自中国南海大陆坡的鱼类标本时,发现了该属的另一种雀尖嘴鱼(Gomphosus caeruleus Lacepède,1801),为中国新纪录种。本种的主要鉴别特征为:体呈浅黄褐色(雌)或深黑色(雄);吻部特别延长呈管状;体长为体高的4.2倍,为头长的2.6倍;背鳍Ⅷ-13,臀鳍Ⅲ-11,胸鳍i(不分支)+14(分支);脊椎骨25;鳃盖条7;体被中大圆鳞;侧线完全,在背鳍条的后部下方急剧向下弯折,侧线有孔鳞片27;头部仅鳃盖上部有9枚呈三角状排列的小鳞;背鳍起点前方有鳞8行;背鳍第一至第三鳍棘间的鳍膜具1黑斑;尾鳍截形。     

Group spawning results from the streaking of small males into a sneaking pair: male alternative reproductive tactics in the threespot wrasse Halichoeres trimaculatus

In many protogynous wrasses, large males with bright coloration (terminal phase males, TP males) establish mating territories and pair-spawn with females. In contrast, small primary males with drab coloration (initial phase males, IP males) are non-territorial and adopt three alternative reproductive tactics—group spawning, streaking, and sneaking. We investigated how IP males of the threespot wrasse Halichoeres trimaculatus use these tactics in different situations. The mating frequency of the IP males was positively correlated with their courtship frequency, but not with their body size. Larger IP males tended to attack the smaller ones at the mating sites. This indicates that the larger IP males attempted to exclude the smaller ones from mating with the intention of minimizing the number of IP males involved in group spawning and ultimately leading to pair spawning (sneaking). However, the larger IP males were unable to completely exclude the smaller males because the intensity of the attack by the larger IP males was weak. Consequently, the smaller IP males could easily streak into the sneaking of larger IP males, thereby resulting in group spawning.