The Behaviour of the Mediterranean Tripterygion Species (Pisces,Blennioidei)

The behaviour of the three mediterranean benthic fish Tripterygion tripteronotus, T. xanthosoma, and T. melanurus is described from observations in the field and observations on captive animals. The ♂♂ defend a territory only during the reproductive season; ♀♀ do not defend a territory. At the height of the breeding season, a male T. tripteronotus on average spawns with four ♀♀ Per day. The ♂ defends the territory against egg predators and cleans the eggs. ♀♀ spawn repeatedly during a spawning season. A spawning pair of T. tripteronotus frequently attracts conspecifics. The majority of these “satellites” are small, sexually mature ♂♂, which do not own a territory themselves. The reproductive strategies of the two types of ♂♂ (territorial ♂♂ and satellite ♂♂) and of the ♀♀ are discussed. On the basis of ethological, morphological, and palaegeographic data the evolution of the eastern-atlantic and mediterranean Tripterygiidae is reconstructed. A bibliography of the literature on eastern-atlantic and mediterranean Tripterygiidae is given. As in their morphology and anatomy, benthic fish show convergent adaptations in their behaviour. Some of these are pointed out and discussed.     

Pheromone-Induced Spawning of Pacific Herring

A spawning pheromone in the milt (semen) and testes of the Pacific herring,Clupea harengus pallasi,is thought to facilitate school spawning of this species. We found that responsiveness to the spawning pheromone was variable among ripe fish (milt-producing or ovulated). Measurement of five principle reproductive steroids in the free form and five steroids in conjugated forms in the plasma of male fish early in the spawning season (newly ripe fish) showed that elevated plasma levels of 3α,17α-dihydroxy-5β-pregnan-20-one and 17α-hydroxyprogesterone coincided with responsiveness to the spawning pheromone in these fish; levels of other steroids did not differ. In contrast, responsiveness to the pheromone by female fish later in the spawning season (ripe-and-holding fish) coincided with lower levels of glucuronated 17α,20β-dihydroxyprogesterone and a lower gonadosomatic index. We suggest that these differences indicate a more advanced mature reproductive state in the responsive individuals among both the newly ripe male and the ripe-and-holding female fish. We found no differences in the level of cortisol in the blood of the herring that could be correlated with differences in pheromonal responsiveness. We conclude that differences in responsiveness to the spawning pheromone coincide to some extent with levels of reproductive maturation but probably not with recent stress.     

Influences of the reproductive cycle on condition of marine catfishes (Siluriformes,Ariidae) in a coastal area at southeastern Brazil

Marine catfishes use estuaries and bays as part of their life cycle for spawning and feeding purposes, respectively. We compared three species of the family Ariidae in two different environmental conditionsa relatively stable bay site and an estuarine site, which differ in their magnitudes of environmental fluctuation to investigate effects of spawning on condition. We found differences in the parameter b (slope) and in they-intercept (a) among species and sexes. The parameter a varied inversely with b, and thus is not a good indicator to express fish condition. Condition factor did not differ between the two sites for species and sexes when we consider the pooled data. Overall condition was associated with reproductive process, and was high before the reproductive season, decreasing during the spawning period in the estuary, then increasing when fish move to the bay (April–August). Temporal segregation in the reproductive period and small-scale movements between the estuary and the bay are the probable mechanisms to optimize the use of the area by the three species.     

The Lek-like Mating System of Halichoeres melanochir (Pisces: Labridae) at Miyake-jima,Japan1

Reproductive behavior and social organization of the labrid fish Halichoeres melanochir were studied at Miyake-jima, Izu Islands, Japan. ♂♂ set up contiguous territories from early to mid-afternoon daily during the breeding season, with ♂♂ at the center of the spawning site experiencing significantly higher spawning success than those at the periphery. Unlike other labrids with lek-like mating systems previously reported, H. melanochir is sexually monochromatic and shows only minimal sexual size-dimorphism. The spawning behavior and mating system are described and compared with current theories on labrid reproductive strategies.     

Polygynous Mating System of Trimma okinawae (Pisces: Gobiidae) at Kagoshima,Japan with a Note on Sex Change

Mating system, social structure and reproductive behaviour of the gobiid fish Trimma okinawae were studied at Akamizu, Kagoshima, Japan. Mating system of this species is polygyny. There were two types of habitat-related distribution patterns of male and female home ranges: females have home ranges outside a small territory of the male; female home ranges are covered by male territory. Spawnings take place with a cycle of four to five days during the spawning season of June to Sept. In the morning of the day of spawning, males stay at the spawning sites. Females visit the site and spawn with the male. On days between spawnings males exhibit courtship displays at female home ranges. Higher reproductive success is not connected with frequency of such courting of the male, but with male size. The largest female of a social unit changes into a male when the dominant male is removed, which shows that T. okinawae is a hermaphrodite.     

Observations on the reproductive biology of Mastacembelus armatus (Lacèpede)

Some observations on the biology of Mastacembelus armatus (Lacepède) from Muzaffarnagar (U.P., India) have been made during the period July 1966 to June 1969. At a particular stage of maturity of the fish there is a close relationship between the gonad weight and the body weight which helps in determining the breeding period of the fish. Both male and female fishes mature simultaneously. The gonad weight influences the relative condition, while the visceral weight does not exert any significant effect on it. The development of the female gonads greatly affect the curve of relative condition, more than the development of male gonads, though the curve for male fish also shows a steady rise and fall in the seasonal variations of the relative condition. Seasonal fluctuations in relative condition correspond to its spawning season. In M. armatus , the presence of two peaks in the curve confirm two breeding seasons. The present studies have also elucidated to a certain extent the important aspect of the maturation and spawning habits of M. armatus in North India. The fish has two breeding seasons of short duration during June and July and again in November. The mature ovaries of each season contain slight maturing ova of next season along with mature ova of the present season. The entire stock of ova measuring 0.16 mm and above are shed during spawning.     

Two spawning seasons and mating system of the bastard halibut, Tarphops oligolepis

We investigated the breeding habits of the bastard halibut, Tarphops oligolepis, in the southwest of Kyushu Island, Japan. This fish was found to have two spawning seasons in a year (around July and November); individual fish spawned over the two spawning seasons. During the spawning seasons, males established territories. Home ranges of females overlapped with those of other females and with territories of plural males. The courtship partner changed during a day, and multiple matings among both sexes were observed during a spawning season, suggesting that T. oligolepis bred promiscuously. This is the first report of the mating system among Paralichthyidae. Received: October 18, 2000 / Revised: May 7, 2001 / Accepted: July 9, 2001     

Interspawning interval of wild female three-spined stickleback Gasterosteus aculeatus in Alaska

The interspawning interval, or spawning frequency, of wild three-spined stickleback, Gasterosteus aculeatus , was estimated using histological examination of postovulatory follicles (POF). Females in Alaskan lakes appeared to have as much as a 48 h delay between ovulation and ovoposition, yet the POF method could still be used to estimate the interspawning interval. In two Alaskan lakes the interspawning interval was estimated to range from 2·2 to 7·8 days among individual female G. aculeatus . These estimates were consistent with the range (2·5 to 5 days) of previous estimates among individual females from laboratory observations of spawning G. aculeatus , as well as anecdotal accounts of spawning intervals reported from wild populations in Canada (5–10 days). The interspawning interval of females increased during the course of the spawning season in Alaska, showing that the majority of female spawning activity occurred during the earliest portion of the approximate 6-week reproductive season. The increased interspawning interval appears to be related to a previously reported decrease in body condition in reproductive females during the breeding season. Thus, female G. aculeatus may be unable to sustain the initial rate of reproduction as energy stores that support the rapid growth of vitellogenic oocytes are depleted.     

Maturity and fecundity of golden grey mullet (Liza aurata Risso, 1810) in Iranian waters of the Caspian Sea

The objective of the study was to determine some reproductive parameters in the golden grey mullet (Liza aurata Risso, 1810) during two periods half a decade apart while also trying from limited data to identify changes in fecundity over the past half century. Maturity and fecundity of golden grey mullet caught in Iranian waters of the Caspian Sea is not well documented and were thus studied during several seasonal cycles during 2002–2004 to establish basic data on reproduction in the area. The fork length (FL) of 462 sampled fish was between 22.1 and 51.9 cm. The fork length–weight relationship derived from all fish was W = 0.0118FL^2.964. Overall male to female ratio was 1 : 1.42. The reproductive season extended from October to December. Fifty percent of sexual maturity was at FL 26.0 cm. Mature gonads were present in 20% of fish at age 3, 63% at age 4, 88% at age 5, and 97% at age 6. Individual absolute fecundity of the golden grey mullet ranged from 113 386 to 1.47 million eggs, with a mean (±SD) of 451 963 (±274,114.2). An overlap exists between the spawning and fishing seasons. Therefore, the start of the fishing season should be delayed for 1 month in order for stocks to complete their spawning.     

Relationship between hatch date and first-summer growth of five species of prairie-stream cyprinids

Stream fishes often exhibit a bet-hedging multiple spawning reproductive strategy. In many species, the reproductive season lasts several months. This exposes young fishes to varying environmental conditions that may differentially affect growth. We studied the effect of hatch date on first-summer growth among members of a prairie-stream fish assemblage. The reproductive season in both years of the study was protracted, lasting from April through August. Due to intermittent stream-discharge, there were two distinct periods during which most species successfully reproduced. In general, growth rate was greater among individuals with an early hatch date than among those with a later hatch date. Multiple regression models indicated that hatch date was related to growth in all study species with one exception (red shiner, Cyprinella lutrensis). The results of this study provide evidence that young-of-the-year of multiple spawning stream-fish species that are spawned late in the season may grow at a slower rate than young spawned earlier in the season.     

Reproductive biology of the endangered Oxleyan pygmy perch Nannoperca oxleyana Whitley

The reproductive biology of the Oxleyan pygmy perch Nannoperca oxleyana is described from simultaneous studies of wild populations in north-eastern New South Wales and mature fish held in aquaria. In the wild, 50% of males and females matured at total lengths of 24·0–25·9 and 28·0–29·9 mm, respectively. The species displays sexual dichromatism during the spawning season, with males developing more intense red and brown fin and body colouration, and black pelvic fins. Captive male broodfish displayed territoriality during the breeding season, closely guarding sites within artificial, plant-like substrata in which pairs of fish spawned adhesive eggs. Protracted serial spawning of wild and captive fish occurred from September to April and May at mean water temperatures ≥16·6° C and day length ≥10·7 h. Captive broodfish spawned on an average of 57% of days during the 256 day spawning period. Gonado-somatic indices averaged 0·7% for all ripe males and 4·1–4·2% for all ripe females collected. Mean total and batch fecundities of captive females were 1323 eggs per fish and 7·8 eggs per fish per day, respectively, and relative fecundity was 587 eggs g⁻¹ of body mass. Batch fecundity of wild females was estimated at 7·8 eggs per fish. The adaptive significance of this reproductive strategy in a harsh, variable environment is discussed.     

Reproductive cycle in female Waigieu seaperch (Psammoperca waigiensis) reared under different salinity levels and the effects of dopamine antagonist on steroid hormone levels

Waigieu seaperch (Psammoperca waigiensis) is a tropical marine finfish species, which may inhabit wide range of salinity during the entire life cycle. Regardless of the wide salinity tolerance, little is known about how salinity may influence the reproductive endocrinology of this important tropical species. In the present study, we investigated the seasonal variations in steroid hormone levels, oocyte maturation (OM) and ovulation in fish reared under different salinity levels. In addition, we investigated the effects a dopamine antagonist (domperidone: DOM) during the peak spawning period. Mature brood fish at 3 years old were cultured in four different salinities of 5, 10, 20 and 30‰ (part per thousand, ppt) from March to December 2007. Blood samples were collected monthly and key steroid hormones (testosterone (T), 11-ketotestosterone (11-KT), 17β-estradiol (E2) and progesterone (P)) levels in female fish plasma were analyzed using enzyme immunoassay method. OM, ovulation and several reproductive performance indexes were evaluated twice per month during the breeding season. Plasma hormone analysis showed significant differences in fish groups cultured in different salinities during the seasonal cycle. The gonadosomatic index (GSI) gradually increased from March, peaking in July at 10 and 30‰, and then decreased thereafter until December. Plasma steroid levels (E2, T, 11-KT and P) were observed in variable concentrations during the spawning period and showed monthly fluctuations that were apparently salinity dependent during on and off-seasons. Interestingly, 11-KT levels were found in small amounts in female fish and peaked in September at salinities of 10 and 20‰. DOM exposure produced significant differences in steroid hormone levels that were apparently dependent on dose, exposure time and the individual hormone. The present study indicated that holding Waigieu seaperch brood fish in different salinities during the breeding season produced significant effects on gonadal development and spawning incidences. The first spawning was observed on 8th of April for all groups after 100% water exchange at night. No significant differences of absolute and relative fecundity were observed between groups. Fish held at 10 ppt salinity during the breeding season spawned naturally, but maturity and spawning rates were reduced and no hatching was observed at the same salinity. Fish holding at 5‰ resulted to 100% mortality in brood fish. This indicated that salinity limits for oocyte maturation or ovulation and subsequent reduction in spawning, but embryonic development requires a higher salinity. The effect of salinity on embryo development and hatching rate suggests that in breeding season the brood fish spawned in areas where the salinity and other parameters are favorable.     

Electric signalling and reproductive behaviour in a mormyrid fish, the bulldog Marcusenius macrolepidotus (South African form)

Bulldog fish (Marcusenius macrolepidotus) generate short (<1 ms) electric-organ discharges (EODs), separated by much longer and highly variable interdischarge intervals (IDIs). We observed overt behaviour and electrical activity during reproductive behaviour in a male and in a female bulldog, and identified IDI patterns with putative signal functions. In contrast to Pollimyrus adspersus and Pollimyrus isidori, in which an elaborate and extended courtship precedes spawning proper, our fish started spawning almost immediately when we allowed the female to enter the males territory. The male did not construct a nest, and neither parent provided parental care. The male showed very little aggression towards the intruding female. Fish spawned in bouts near the males hiding place, and eggs were scattered by the females vigorous tail flips as she left the spawning site, only to return shortly thereafter. During spawning bouts, both fish generated highly stereotyped IDI patterns: the male generated a series of IDIs gradually decreasing from about 200 ms to about 55 ms that was abruptly terminated by a long IDI. The female generated a series of relatively regular IDIs (about 54 ms) that was followed by a marked increase in IDI duration (the probable time of spawning). Finally, a sharp decrease in IDIs to about 20 ms accompanied the females sudden escape from the spawning site. In between spawning bouts, both fish generated series of very short IDIs (high discharge rate, HD) that alternated abruptly with very low-rate inter-HD activity (especially in the male). IDIs as short as 9 ms (male) or 11 ms (female) occurred during HD displays. No visible aggression, in fact very little overt behaviour, occurred during these HD displays in both fish. Agonistic interactions between male and female, outside a reproductive context, were similar to those previously described in male pairs, including overt behavioural patterns such as parallel swimming, antiparallel display and attack, as well as HD displays. When not interacting, fish did not generate HD displays. We suggest the HD display is a communication signal in both reproductive and agonistic contexts.     

Aspects of reproductive biology of Labeo horie Heckel (Pisces: Cyprinidae) in Lake Chamo, Ethiopia

Labeo horie Heckel is increasingly becoming commercially important in Lake Chamo but its reproductive biology in the lake is not well enough to guide its management. Sex ratio, breeding season, length at first maturity and fecundity of L. horie were studied from 1197 fish samples collected between August 1998 and October 1999 in Lake Chamo, Ethiopia. The sex ratio was significantly different (χ ² = 12.12, P < 0.001). The peak‐breeding period was during the rainy months of March to May, during which time more than 90% of both sexes had ripe gonads. The size at maturity ( L _m50 ) of males was 52 cm while the L _m50 of females was 62 cm. The smallest ripe male in the catch was 46.7 cm and weighed 890 g while the smallest ripe female caught was 49.5 cm and weighed 1145 g. The weight of ripe ovaries ranged from 54.3 g to 991.8 g and contained between 68,400 and 1,320,400 eggs. Relative fecundity ranged between 60 and 290 eggs per g of body weight. The relationships between fecundity and total length and between fecundity and total weight were curvilinear, while the relationship between fecundity and ovary weight was linear. L. horie conformed to the general pattern of reproduction in a tropical environment where peak‐breeding activity occurred during the rainy season. In order to protect the spawning population, fishing pressure should be minimized during breeding time at the shallower littoral regions.     

Gametogenesis and Development of Gymnocharacinus Bergi (Pisces, Characidae): Reproductive Mode Relative to Environmental Stability

Gymnocharacinus bergi (Pisces, Characidae) is classified as 'endangered' (IUCN 1996). It has been given particular attention among Patagonian fishes due to the reduction of some of its morphological structures, particularly scales, its extreme southern distribution among the Characiformes and its strong adaptation to a thermal environment in northeastern Patagonia. This paper describes the main aspects of gametogenesis, induced breeding, spawning and development of G. bergi, whose life history traits are related to the peculiar characteristics of its restricted environment. The temperature and flow stability of the Valcheta Stream make many of the environmental variables predictable. Other variables related to photoperiod undergo predictable fluctuation during the year. Gymnocharacinus bergi has synchronous gametogenesis and a rather short breeding season, which is earlier than for Paranensean characids. Its reproductive mode, courtship and spawning behaviour, and the absence of sexual dimorphism are common to other small characins from lotic environments. Gymnocharacinus bergi is a sedentary species with precocial characters, such as low fecundity and slightly adhesive, yolk-rich oocytes which are large in relation to the small size of the female. Larvae are robust, development is indirect and adulthood prolonged. These peculiar characteristics indicate a reproductive style very different from that of the main groups of Patagonian fish fauna.     

Breeding Tubercles, Papillomatosis and Dominance Behaviour of Male Roach (Rutilus rutilus) During the Spawning Period

We studied the relationship between the breeding tubercle ornamentation (i.e. skin roughness) and male pre‐spawning dominance and courtship behaviour in roach (Rutilus rutilus) within an experimental laboratory system. Sexually mature fish were caught during their migration to their spawning pond and their behaviours were studied in an artificial spawning arena. Males behaved naturally both in terms of male–male interactions and attempts to achieve spawnings. Males having many, large breeding tubercles (i.e. rough skin) were significantly more often dominant in our dyadic trials than those with smooth skin. The dominant male in the trial exhibited a more active courtship behaviour than its subordinate rival. Papilloma skin disease did not affect the dominance rank. As a result of the relationship between skin roughness and male dominance, breeding tubercles may be used by the females as a cue for choosing a high‐quality mate in a roach lek. Thus, breeding tubercles might offer a workable tool for examination of sexual selection among cyprinids.     

Male reproductive competition in spawning aggregations of cod (Gadus morhua, L.)

Reproductive competition may lead to a large skew in reproductive success among individuals. Very few studies have analysed the paternity contribution of individual males in spawning aggregations of fish species with huge census population sizes. We quantified the variance in male reproductive success in spawning aggregations of cod under experimental conditions over an entire spawning season. Male reproductive success was estimated by microsatellite-based parentage analysis of offspring produced in six separate groups of spawning cod. In total, 1340 offspring and 102 spawnings distributed across a spawning season were analysed. Our results show that multiple males contributed sperm to most spawnings but that paternity frequencies were highly skewed among males, with larger males on average siring higher proportions of offspring. It was further indicated that male reproductive success was dependent on the magnitude of the size difference between a female and a male. We discuss our results in relation to the cod mating system. Finally, we suggest that the highly skewed distribution of paternity success observed in cod may be a factor contributing to the low effective population size/census population size ratios observed in many marine organisms.     

Reproductive patterns in three species of large coral reef sponges

The type and frequency of reproduction of three common sponge species was monitored histologically and by direct field observations of spawning events over 2 successive years at the reefs of Curaçao. Ircinia strobilina showed year round reproductive activity by the production of spermatic cysts in varying intensities in a major part of the population. Production of oocytes and larvae were only observed in the period from September through April, indicating an actual breeding season of 8 months a year. The sexes in this viviparous sponge seem to be separate, but protandry cannot be ruled out. Less than 10% of the sponge tissue was found to consist of reproductive elements. Neofibularia nolitangere is a gonochoristic oviparous sponge with a short annual breeding season of 2 months, in which two successive, highly predictable, short spawning periods occurred synchronously for the whole population. Up to half of the sponge tissue was transformed to reproductive elements. Agelas clathrodes showed low reproductive activity. Field observation suggests that this sponge is an oviparous hermaphrodite, probably annually releasing male and female gametes synchronously in a varying number of individuals of its population during a short breeding period.The variation in reproductive patterns in this small group of large massive coral reef sponges spans a range similar to that found in the morphologically highly variable group of stony corals and illustrates their ecological differentiation on the reef.     

Annual changes in brain concentration of arginine vasotocin and isotocin correspond with phases of reproductive cycle in round goby,Neogobius melanostomus

Reproductive cycle of seasonally breeding fish is synchronized with changes of photoperiod and temperature in environment. We hypothesize that arginine vasotocin (AVT) and isotocin (IT) are involved in timing and synchronization of seasonal reproductive activity in the round goby (Neogobius melanostomus). To verify this hypothesis, we examined the annual profiles of brain AVT and IT in round goby males and females in relation to their reproductive cycle. Wild round gobies were exposed to annual environmental changes in their natural habitats from where they were sampled monthly over a year. AVT and IT were measured using HPLC with fluorescence detection preceded by solid-phase extraction. This study shows seasonal variations in brain AVT and IT levels. Profiles of changes were similar in males and females: the peak of AVT was observed before spawning in March-April, whereas that of IT during spawning in May–June. Furthermore, the lowest AVT level was noted out of breeding season from November to January, while the level of IT decreased immediately at the end of the spawning. The results show that high AVT levels correlate with pre-spawning period whereas the highest IT levels correspond to spawning. A significant decline in AVT and IT in non-spawning season coincided with the quiescent phase of gametogenesis in both sexes.