Assessing the relative importance of temperature,discharge, and day length on the reproduction of an anadromous fish (Alosa alosa)

1. Climate change threatens anadromous fishes such as the allis shad (Alosa alosa) populations of which have declined since the 20th century in Europe. Sensitivity to climate change could be quantified by determining the fish’s spawning behaviour, defined as the timing of reproduction (i.e. spawning events) as a function of temporally variable environmental factors. The cues that fish use to time reproduction could determine their response to climate change.
2. A machine learning technique (boosted regression tree) was calibrated using a 14-year dataset composed of daily measures of environmental factors and fish occurrences during reproduction. The boosted regression tree provides complete insight into the complex relationship between the spawning probability, i.e. the probability for a fish to reproduce, and environmental factors that might evolve with climate change.
3. The spawning probability was positively related to day length (44.6%) and water temperature (34.7%) and negatively related to river discharge (20.7%). Optimal reproductive conditions corresponded to a difference in day length between 0 and 0.04 hr, a water temperature between 15 and 26°C and a river discharge between 55 and 665 m³/s; these conditions are currently being utilised by allis shad populations in the Garonne and Dordogne rivers, France.
4. This study highlights the relative influence of environmental factors on the observed spawning period as well as the evolution of habitat suitability during the 14-year period. The novelty of this study stems from assessing population process data, i.e. the occurrence of fish reproduction, rather than mere occurrence data in an ecological niche model study. Climate change may lead to a shift in spawning phenology, as the water temperature and river discharge will also change. Therefore, conservation plans need to integrate these effects on spawning grounds.

     

Courting Failure in a Pencilfish,Nannostomus b. beckfordi

We analysed a sample of 4341 activity bouts from 12 male Nannostomus b. beckfordi interacting with ♀♀. Only 22 % of the gamopractic bouts ended in spawning. In 50 % of the bouts the pair separated without spawning or interference, partly as a result of male aggression. Interference frcm conspecifics was also a major cause of failure, terminating 28 % of the gamopractic bouts. Successful courtship bouts contain more gamopractic behaviour than do abortive bouts, even in the first 6 s, and also show greater stereotypy.     

Patterns of Aggression and Operational Sex Ratio Within Alternative Male Phenotypes in Atlantic Salmon

The intensity of male–male aggression during mating is predicted to increase with the operational sex ratio (OSR) (the ratio of sexually active males to females). We observed aggressive behaviour in relation to OSR within alternative phenotypes (large anadromous males and small ‘sneaker’ mature male parr) of Atlantic salmon, Salmo salar, as they competed for access to anadromous females in large outdoor arenas immediately prior to spawning events as well as throughout the spawning season. Anadromous males were primarily aggressive outside of spawning events, and their aggression increased with OSR over a narrow range of 0.08–4. By contrast, mature male parr were aggressive just prior to spawning, with a decrease in aggression over a broad range of OSRs from 1 to 7.4. Similarly, literature data for three other salmonid species indicated a decrease in aggression with increasing OSRs over a range of 1–6.33. These observations suggest that there is considerable variability in competitive behaviour, even within alternative phenotypes. Because our data are derived from repeated observations on the same individuals of different genetic origin, further confirmation of these findings is desirable. Nevertheless, our study underscores the importance of measuring competitive behaviour and OSR at ecologically relevant spatial and temporal scales, both of which may differ between alternative maturation phenotypes.     

Looking for love under the ice: Using passive acoustics to detect burbot (Lota lota: Gadidae) spawning activity

1. Burbot (Lota lota: Gadidae) is a difficult species to manage effectively due to its preference for deep-water habitats and under-ice spawning behaviour, resulting in a poor understanding of its reproductive activity. However, the use of acoustic signalling by burbot as part of their mating system has recently been described and this behaviour may provide a means of investigating questions regarding the spatial and temporal distribution of spawning aggregations using passive acoustic monitoring.
2. We used audio and video recording to confirm that burbot vocalise and that these vocalisations can be detected under field conditions as well as to characterise the relationship between burbot acoustic signalling and spawning behaviour. We also evaluated the feasibility of locating and monitoring burbot spawning aggregations in real time using passive acoustics.
3. Burbot vocalisations were difficult to identify with only about 6% of the recordings containing calls being successfully identified as such in the field. Burbot vocalised more often between sundown and sunrise than during daylight hours. Calls recorded at night tended to be lower frequency, longer duration, and have lower bandwidth than those made during the day.
4. Burbot vocalisations could not be recorded in conjunction with video recordings of spawning activity, indicating that burbot may not call during active spawning, but may use acoustic communication to signal the onset of reproductive readiness and to form pre-spawning aggregations.
5. While burbot calls were readily identifiable, observers had a difficult time identifying burbot calls in real time under field conditions. Passive acoustic monitoring demonstrates considerable potential as a management tool to locate burbot spawning grounds and identify periods of activity, but may not be an appropriate technique for monitoring spawning activity in real time.

     

Sperm allocation pattern during a reproductive season in the copulating marine cottoid species, <Emphasis Type="Italic">Alcichthys alcicornis</Emphasis>

The sperm allocation pattern of a copulating marine cottid fish, Alcichthys alcicornis, was investigated. A total of 86 mating events using six males were conducted in aquarium tanks over 10 days, and in 36 of them, spermatozoa were collected using a false copulation method. Males released 3–8 × 10⁸ spermatozoa in early events, with the number decreasing gradually during subsequent mating events. This sperm allocation was represented as an “early investment and tapering” pattern. It was discussed why males have significantly higher sperm release in early spawning events. The reproductive behavior consists of spawning and subsequent copulation. Spermatozoa have the ability to fertilize eggs from multiple clutches, and in earlier produced clutches the level of sperm competition should be relatively low. In addition, if early spawn happens to be the first spawn with a female, spermatozoa that are released into the water column after spawning are responsible for fertilizing the female’s first clutch. The probability of this occurring should decrease dramatically as the season progresses, due to the highly synchronous seasonal spawning of females. All of these factors should select for high sperm numbers in early ejaculates. Based on such reproductive ecology of A. alcicornis we hypothesize that this sperm allocation pattern is an adaptive reproductive strategy in response to egg availability and sperm competition occurring within the ovarian cavity.     

Coastal zone use and migratory behaviour of the southern population of Mugil liza in Brazil

We analysed the ratios Sr:Ca and Ba:Ca in the otoliths of 55 adults of the southern population of Mugil liza in Brazil (Paraná to Rio Grande do Sul) to investigate its coastal zone use and migratory behaviour. All individual M. liza analysed had Sr:Ca and Ba:Ca values indicating that their birth was in the marine environment, which is consistent with the southern population migration to spawn in the ocean,. Juveniles exhibited at least three coastal use and recruitment strategies (contingents): the majority (89%) of M. liza juveniles migrated toward brackish water. They entered the estuary before completing the first year of life (64%) or after (25%) their first year of life. The remaining 11% did not appear to enter brackish or freshwater water as a nursery or at any point in their life cycle. Some adults returned to the estuary after spawning in the ocean but others (of both sexes) never returned to the estuary after spawning, remaining in the marine environment. The pattern of juvenile habitat use in the Brazilian southern population of M. liza seems to be recurrent throughout the extent of its distribution as a consequence of the reproductive spawning aggregation behaviour, which mixes all contingents (with marine or estuarine preferences).     

Evolution of mating systems in coral reef gobies and constraints on mating system plasticity

Social and mating systems can be influenced by the distribution, abundance, and economic defendability of breeding partners and essential resources. Polygyny is predicted where males can economically defend multiple females or essential resources used by females. In contrast, monogamy is predicted where neither sex can monopolise multiple partners, either directly or through resource control, but where one mate is economically defendable. The mating system and reproductive behaviour of five species of coral reef goby were investigated and contrasted with population density and individual mobility. The two most abundant species (Asterropteryx semipunctatus and Istigobius goldmanni) were polygynous. In contrast, the less populous and more widely dispersed epibenthic species (Amblygobius bynoensis, Amblygobius phalaena and Valenciennea muralis) were pair forming and monogamous. All five species had low mobility, mostly remaining within metres (3 epibenthic species) or centimetres (2 cryptobenthic species) of a permanent shelter site. Interspecific differences in the mating system may have been shaped by differences in population density and the ability of reproductive individuals to economically defend breeding partners/sites. However, in a test of mating system plasticity, males of the three monogamous species did not mate polygynously when given the opportunity to do so in experimental manipulations of density and sex ratio. Mate guarding and complex spawning characteristics, which have likely co-evolved with the monogamous mating system, could contribute to mating system inflexibility by making polygynous mating unprofitable for individuals of the pair forming species, even when presented with current-day ecological conditions that usually favour polygyny.     

A method for tracking the behaviour of mature and immature salmon parr around nests during spawning

A remote monitoring system was developed to provide information on the behaviour of mature and immature Atlantic salmon Salmo salar parr at nests during the spawning season. An octagonal passive integrated transponder (PIT) detector (0·865 m maximum diameter) designed to surround nests of Atlantic salmon was used to identify individual salmon parr present at 38 spawning events in three circular spawning channels. The range of the detector for PIT tags presented in the optimum orientation was 2·4 cm (range between tags 1·7–3·0 cm). Using a sub-sample of 20 spawnings, the mean efficiency of the detector (number of fish passes registered relative to number of passes observed on video) was 70·5% (range 32-100%). There were no significant effects of time from spawning, total number of registrations, body size or maturity status (mature or immature) on efficiency. However, fish were more likely to be detected entering nests than leaving, as departures were more rapid and higher in the water column. The PIT detector did not affect the numbers of parr at spawnings or between spawning intervals of females, and allowed for the individual identification of 65 of the 72 parr observed in nests during spawning. In all cases where certain identifications were not possible and the video was of satisfactory quality, this was due to obstruction of the camera view by anadromous fish. The remote monitoring system was thus effective in identifying behavioural differences, and only one of 20 immature parr was ever detected during the period encompassing 10 min before and after spawning compared with 30 or 40 mature parr.     

Mating frequency positively associates with fitness in Ophraella communa

1. Why animals mate multiple times, owing to the lack of immediate fitness benefits, presents an intriguing problem for evolutionary biologists. Yet, the profusion of this behaviour suggests it must be maintained by natural selection via increased performance. 2. The possible benefits of multiple mating using the leaf beetles Ophraella communa LeSage, the biological control agent of the invasive common ragweed Ambrosia artemisiifolia L., were studied and the fitness consequences of single, twice, three, four, and unrestricted mating events were assessed. 3. Overall, it was observed that the number of copulation events was positively associated with fitness parameters of the insects. Insects performed the best under unrestricted mating regimes, with average increases of 48% in longevity, 75% in fecundity, and 55% in egg hatch rate. In addition, females that experienced unrestricted access to mates maintained very high viability over their entire reproductive lives. Nevertheless, insects also performed better when allowed to mate four times compared with once or twice. 4. The present findings thus support the hypothesis that multiple‐mating behaviour is maintained owing to increased fitness benefits in the current and the next generation. Selection for re‐mating is, therefore, expected in field populations, which is likely to happen naturally owing to the aggregate lifestyle of O. communa.     

Some effects of external factors upon the reproductive behavior of the grass frog Rana t. temporaria L. (Ranidae,Anura)

Summary The reproductive period of Rana temporaria can be subdivided into a prespawning period and a spawning period. During the prespawning period only a few Rana temporaria, most of them males, are active in the spawning biotope. There is no calling activity, and deposition of spawn rarely occurs. The time of onset of the prespawning period is variable. In this period the frogs are highly responsive to a drop in the temperature of air and water, burying themselves in the bottom or leaving the spawning waters.By contrast, many animals participate in the spawning period. Migration to the spawning ground takes place chiefly at night. The frogs engage in mating activity immediately upon arrival, and both males and females depart as soon as they have spawned, migrating away in directions corresponding to those of the immigration. During the spawning period there is no demonstrable response of the grass frogs to weather conditions. Rana temporaria begins its spawning period at the so-called set time only in meteorologically normal years. When meteorological conditions are unusual, the spawning period can begin as much as 10 days earlier or later.Possible external timing signals for the onset of migration include temperature in combination with day length, and a drop in atmospheric pressure accompanied by rainfall.Herrn Professor Dr. Rolf Danneel zur Vollendung des 75. Lebensjahres gewidmet     

Deepwater broadcast spawning by Montastraea cavernosa, Montastraea franksi, and Diploria strigosa at the Flower Garden Banks, Gulf of Mexico

Broadcast spawning by corals is a tightly synchronized process characterized by co-ordinated gamete release within 30–60 min time windows once per year. In shallow water corals, annual water temperature cycles set the month, lunar periodicity the day, and sunset time the hour of spawning. This tight temporal regulation is critical for achieving high fertilization rates in a pelagic environment. Given the differences in light and temperature that occur with depth and the importance of these parameters in regulating spawn timing, it has been unclear whether deeper coral can respond to the same environmental cues that regulate spawning behaviour in shallower coral. In this report, a remotely operated vehicle was used to monitor coral spawning activity at the Flower Garden Banks at depths from 33 to 45 m. Three species Montastraea cavernosa, Montastraea franksi, and Diploria strigosa were documented spawning within this depth range. All recorded spawning events were within the same temporal windows as shallower conspecifics. These data indicate that deep corals at this location either sense the same environmental parameters, despite local attenuation, or communicate with shallower colonies that can sense such spawning cues.     

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.     

Isolation and characterization of eight dinucleotide microsatellite loci from two closely related clupeid species (Alosa alosa and A. fallax)

Eight dinucleotide microsatellite loci were developed through an enrichment protocol for allis shad (Alosa alosa) and twaite shad (A. fallax). Cross‐species amplification was successful for all loci isolated. The number of alleles per locus ranged from three to nine for A. alosa and from two to seven for A. fallax, while the observed heterozygosity ranged from 0.267 to 0.926 and from 0.240 to 0.727, respectively. These markers will constitute useful tools for studies of population structure and gene flow between two closely related hybridizing species.     

Identifying spawning events of greater amberjack using accelerometers

Direct observations of spawning events of large free-swimming migratory fish are difficult in nature. However, behavioural changes specific to spawning events of fish species, i.e. swimming depth or acceleration of body motion using data loggers attached to the body, have successfully been used to identify spawning. In this study, we observed the spawning behaviour in an experimental tank of a pair of greater amberjack Seriola dumerili, which were matured by injection of gonadotropin, by attaching an acceleration data logger, an accelerometer. The male and female were observed to vibrate their bodies during the moment of spawning. Analysis of the acceleration data showed the simultaneous appearance of a dominant cycle (cycle indicating the highest amplitude in 1?s) under 0.4?s continuing over 7?sand dominant amplitude over 0.4 indicating the time of the spawning in both sexes. These characteristics are useful for the development of an algorithm to detect the spawning behaviour, allowing us to develop a new data logger with an on-board algorithm for detection of spawning behaviour. Before development of this system, we need to develop new algorithms for separation of spawning behaviour from other similar large motion behaviours, particularly from feeding and prey avoidance behaviour.     

Diel and lunar spawning periodicity of the hawkfish Paracirrhites forsteri (Cirrhitidae) on the reefs of Kuchierabu-jima Island, southern Japan

We observed spawning behavior of the hawkfish Paracirrhites forsteri on reefs of southern Japan. Spawning generally occurred after sunset, prior to the full and new moon with semi-lunar spawning peak periodicity. No egg predation was observed in spawning after sunset, and high tide often occurred at dusk in the lunar phases. Thus, diel timing and lunar synchronicity may increase larval survival. We found that the mating activity tended to start earlier in the day during early mating season than during mid-to-late mating season. The advantages of the earlier start of mating activity were also examined in relation to adult biology contexts.     

Primary and secondary oocyte growth dynamics in anadromous semelparous Allis shad Alosa alosa

We analysed the ovarian dynamics of the anadromous semelparous allis shad Alosa alosa for which our working hypothesis was that mature pre-spawning females would have very low or even exhausted primary growth (PG) oocyte reserves; semelparity has been linked with the depletion of the pool of PG oocytes. To test this hypothesis, the PG oocytes were enumerated, their recruitment pattern to the secondary growth (SG) phase was analysed and their potential replenishment from the pool of oogonia was examined in females caught very close to the Mondego River mouth, in central Portugal and along the river. The development of the SG oocytes was also analysed, the fecundity (batch, total and annual) values were estimated and the intensity of atresia was quantified. Ovarian samples and histological sections were investigated in parallel. A dynamic recruitment pattern of PG oocytes to the SG phase was revealed, where all PG oocytes were recruited and were not replenished by oogonia. Annual fecundity was subject to down-regulation due to atresia prior to spawning and its size was multiple times higher than the size of batch fecundity. Lack of population synchronicity in ovarian development and spawning migration was also observed. This multifaceted analysis of the ovarian dynamics of this species will contribute to management efforts for this critically endangered and economically important fish throughout its geographical distribution. The results reported in this study will also assist in unravelling the complexity of the early processes of oogenesis in fish.     

Sounds produced by spawning fishes

Synopsis Low frequency sounds are shown to be associated with the spawning of two Caribbean coral reef fishes: the hamlet, Hypoplectrus unicolor (Serranidae) and the striped parrotfish, Scarus iserti (Scaridae). Both fishes produce distinctive sounds while broadcasting gametes in midwater. H. unicolor produces sounds via muscle stimulation of the swimbladder. Fin movements among group spawning S. iserti produce hydrodynamic noise. Although reproductive behaviors of these two species have been previously studied in detail, the association of sounds with mating is new. The mating sounds cannot be easily detected by human hearing underwater but are recordable using a hydrophone. The sounds are distinct and recognizable enough to allow counting and acoustic mapping of mating events in these species.     

Reproductive Success Associated with Territoriality, Sneaking, and Grouping in Male Rose Bitterlings, Rhodeus ocellatus (Pisces: Cyprinidae)

The spawning success of male rose bitterlings, Rhodeus ocellatus, adopting an alternative reproductive style, was estimated through behavioural data and electrophoretic paternal analyses in field observations and experiments. Three mating patterns were observed: territoriality, sneaking, and grouping. Mating patterns depended on a male's relative size and on local male density (the number of males around a spawning spot: a mussel). Spawning patterns (pair spawning, pair spawning with sneaker, and group spawning) varied with local male density. Time-budget data of the territorial males indicated a trade-off between chasing and courtship behaviour as local male density changed. Females deposited appoximately only 1 egg per egg-laying into the mussels. As a result of isozyme analysis, a minimum of 12% (two out of 17) of the offspring in the sample were found to have been fathered by sneaker males in pair spawning with sneaker. I scored through behavioural data the mating success per spawning for each pattern, on an individual basis. The average reproductive success per spawning for each pattern was: territorial (0.61), sneaking (0.31) and grouping (0.11), and thus the successes of the patterns were not equal. Accordingly, the alternative reproductive styles of male rose bitterlings are best interpreted as alternative phenotypes in a conditional behaviour.     

Unusual Pre-copulatory Behaviour in the Hermaphroditic Planarian Flatworm,Dugesia gonocephala (Tricladida,Paludicola)

Hermaphrodite mating behaviour is poorly understood, particularly in species with internal fertilization and mutual penis insertion. We collected detailed recordings on the frequency, timing and outcome of the mating sequence of the simultaneous hermaphroditic flatworm Dugesia gonocephala (Tricladida, Paludicola). Mating in this species differs from that in other planarians in that receptive partners show a stereotypic pre-copulatory behaviour which results in copulation in only 17% (n = 342) of all attempts. It includes an unusual phase during which one partner glides on top of the other and first the lower, then both individuals, spread out and flatten. Genital intromission is not possible in this position. All observed copulations (n = 57) were preceded by this behaviour and most mating sequences were interrupted at this stage. Pairs were seen starting new mating sequences up to 11 times. Which animal lay on top varied randomly within a series of attempts. Cocoon production was a good predictor of mating activity, and copulations mainly occurred during the night. Copulations lasted between 24 min and 9.3 h (mean = 4.7 ± 2.3 h) and penises were mutually inserted. In the field, 99% (n = 70) of all matings involved reciprocal spermatophore exchange, compared with only 50% in the laboratory (n = 26). The likelihood of reciprocal spermatophore transfer increased with increasing duration of copulation. Duration was independent of the events that took place during courtship. We discuss the possibility that partners interrupt a copulation when there is no guarantee of reciprocal spermatophore transfer.