Is the timing of spawning in sparid fishes a response to sea temperature regimes?

Published spawning seasons of sparid fish were investigated to determine if there were consistent patterns that could be related to large-scale physical variability, and whether these relationships were species-specific or characteristic of higher taxonomic groupings. For individual species, genera and the family Sparidae as a whole, there was a consistent pattern; spawning at lower latitudes was concentrated close to the month of lowest sea surface temperature, while spawning at higher latitudes was more variable with greater deviations from the month of minimum sea surface temperature. The distribution of sparids may be limited by a lack of tolerance of one or more early life-history stage to high water temperatures, so targeting spawning to the coolest part of the year could be a tactic allowing maximum penetration into warmer waters. Such a link between the physiology of early life-history stages and timing of spawning could have direct consequences for patterns of distributions over a number of taxonomic scales. If there are similar constraints on the reproduction of other species, even minor increases in water temperature due to global warming that may be within the tolerance of adults, may impose constraints on the timing of spawning, with flow-on effects for both species and whole ecosystems.     

Ocean current variability and the spawning season of Hawaiian reef fishes

Synopsis The spawning patterns of four Hawaiian reef fishes with similar reproductive habits, but different biogeographic distributions were studied from September 1980 to October 1981. Two species are Hawaiian endemics [Centropyge potteri (Pomacanthidae) and Chaetodon multicinctus (Chaetodontidae)] and the other two have pan-tropical Pacific distributions [Ctenochaetus strigosus and Zebrasoma flavescens (Acanthuridae)]. All showed increased spawning activity from January to July, the prevalent pattern among a majority of coastal marine fishes in Hawaii. Environmental correlatives to the period of peak reproduction include cycles of (a) daylight length and temperature which probably function as proximate cues and (b) seasonal variations in ocean current patterns which may ultimately affect survival of larvae and dispersal. Peak reproduction takes place during months when (1) mesoscale eddies most likely occur, and (2) the probability is greatest of drifting objects remaining near the islands.     

Crevice spawning behavior in Dionda dichroma,with comments on the evolution of spawning modes in North American shiners (Teleostei: Cyprinidae)

The crevice spawning behavior of Diondadichroma is described for the first time, andcompared to spawning behavior in the genusCyprinella. The evolution of crevice spawningwith respect to other spawning behaviors ofNorth American shiners is examined usingexplicitly phylogenetic hypotheses for thisgroup. We present evidence that broadcastspawning is plesiomorphic and all otherspawning behaviors are independently derived. There is evidence that crevice spawning hasevolved independently at least three timeswithin the shiner clade. There is no supportfor an evolutionary transition between eggclustering and crevice spawning. Nestassociation, spawning on habitat prepared byother species, has also evolved multiple timeswithin this clade. Evolution of spawning inshiners is best described by phylogeneticstasis with several independent origins ofspecialized spawning stragegies.     

Habitat correlates of the distribution and biomass of Seychelles' reef fishes

Synopsis Relationships between quantitative measures of habitat type and the biomass of Chaetodon, Scarus and Parupeneus species were investigated across 35 reef sites in the Inner Seychelles Group. Multiple regression was used to determine the proportion of variance in biomass between sites which could be explained by depth, exposure, vertical relief, topographic complexity, live coral cover, coral rubble cover, rock cover, sand cover, underlying carbonate substrate, underlying sand substrate, underlying rock substrate and an index of fishing intensity. A significant proportion of the variance in biomass was explained by habitat variables and the index of fishing intensity for 7 of 12 Chaetodon species (23–52% of variance explained), 3 of 6 Parupeneus species (33–40%), and 10 of 13 Scarus species (14–46%). Within genera, different groups of habitat variables explained the variance in biomass for different species and, of the variables studied, only the proportion of underlying sand substrate failed to explain a significant proportion of the variance in biomass for any species. Quantitative relationships between the biomass of Chaetodon and habitat were often in accordance with those suggested by previous studies of their ecology, life-history and distribution at other Indo-Pacific locations. However, the habitat associations of the Parupeneus and some Scarus species have not been studied at other locations and clearly warrant further investigation. It was concluded that habitat was an important determinant of the distribution of many Seychelles reef fishes, but that the habitat variables examined were rarely the most important determinant of biomass. However, the inclusion of a procedure to collect habitat data provided a useful means by which to reduce the unexplained variance associated with visual census biomass estimates and therefore improves the possibility of elucidating the effects of other factors on the biomass of Seychelles reef fishes.     

Dry-season spawning in a cyprinid fish of southern India

Synopsis A population of the S. Indian cyprinid fishBarbus melanampyx was sampled monthly through 24 months. Seasonal cycles of the gonado-somatic index (GSI), ovarian stages, male breeding tubercles, spawning behaviour and population structure were assessed. These fish breed strictly seasonally during the main dry period: December/January through April. Comparison with other Barbus species of the same general region led to the conclusion that the patterns of reproductive investment ofB. melanampyx are similar to those of perennial species, and different from those of wet-season spawners. The reasons for this rather unexpected result were found in the more constant conditions prevailing during a dry season as compared to the monsoon. It was argued thatB. melanampyx and the species spawning perennially are in effect small-brood spawners, rather than partial spawners.     

Lunar synchronization of spawning in cichlid fishes of the tribe Lamprologini in Lake Tanganyika

Lunar synchronization of spawning was investigated for eight substrate brooding cichlid fishes belonging to the tribe Lamprologini. Their spawning activities all peaked during the second quarter of the lunar cycle. Comparison between their breeding styles and the degrees of spawning synchronization suggested that the nocturnal guarding-efficiency of eggs, especially exposed ones, is improved by the maximal amount of moonlight during full moon and, in species whose young leave the breeding sites about 2 weeks after spawning, the survival of dispersing young is enhanced by the darkness of moonless nights.     

Population variation in spawning current speed selection in the blacktail shiner,Cyprinella venusta (Pisces: Cyprinidae)

Synopsis Many stream fishes lay demersal eggs. Some species simply scatter the eggs across the substrate, but many place the eggs in protected sites such as crevices (e.g., Cyprinidae:Cyprinella). Eggs laid in crevices may experience increased development times or lower embryo survival due to reduced water exchange rates compared to more open egg deposition sites. If so, the presence of an appreciable current near the crevice may be important for insuring water exchange. However, currents that are too strong may prevent complete insemination or prevent the eggs from adhering to the substratum before they are washed from the crevice. Thus, current speed preferences for spawning may be under strong stabilizing selection. Representatives of four populations of a crevice spawning stream fish (blacktail shiner,Cyprinella venusta), representing environments ranging from a swift stream to a lake, were studied in stream tanks to evaluate female spawning current use. The observed frequency of use of spawning currents was significantly different from random in all populations. Low current speeds were generally avoided, and a speed of ca. 30 cm sec^–1 was used most often. However, significant differences were observed among populations, and the variation correlated well with the apparent range of current speeds found in the four environments. Although other possible explanations cannot be dismissed, the results are consistent with the hypothesis that the populations have become adapted to their local current regimes.Authorship in order of seniority     

Synchronized spawning ofanguilla japonica inferred from daily otolith increments in leptocephali

The exact timing ofAnguilla japonica spawning was determined from analyses of daily otolith increments in leptocephali collected near a spawning area west of the Mariana Islands on July 1–18, 1991. The birth dates of the 54 leptocephali examined (10.2 to 30.5 mm in total length) ranged from May 22 to June 24, 1991, the individuals clearly comprising two age groups, May-born fish (mode May 28) and June-born fish (mode June 21). The data showed thatA. japonica spawns intermittently during the spawning season, with fixed synchronized timing. Each group of leptocephali collected along three different north-south transects (131°, 134° and 137°E between 10° and 22°N) comprised both May-born and June-born fish. The latter were dominant along the easternmost and middle transects, whereas the May-born fish were more abundant along the westernmost transect. The modal ages of the June-born and May-born fish collected along 137°E on July 1–3 were 13 d and 35 d, respectively, while those of the two age groups collected along 134°E on July 17 and 18 were 28 d and 50 d, respectively. These data show that the interval between the sampling dates for the two transects (ca. 15 d) corresponded closely to the differences in modal ages of specimens from the two transects (15 d) for both the May- and June-born fish, and further, that the difference in modal age between the two age groups (22 d) was the same at both transects. A similar correspondence in total length was also observed between the two age groups at the above two transects. The findings clearly demonstrated parallel westward transport by the North Equatorial Current for both the May- and June-born eel leptocephali, which originated from a spawning area estimated as being between 141° and 143°E.     

Annual cycle of gametogenesis and spawning in a tropical zoanthid,Protopalythoa sp.

Gametogenesis and spawning have been studied since 1986 in a population of Protopalythoa sp. (Anthozoa, Zoanthidea) from Orpheus Island, Great Barrier Reef. Fertile zooids were gonochoric or hermaphroditic with oocytes and sperm vesicles intermingled in the same mesentery; colonies were single sex or mixed. Oocytes arose in macrocnemes below the actinopharynx and were first observed in July. Their mean diameter increased from < 50 µm to 160–240 µm by November, by which time they contained zooxanthellae. Female zooids each produced 800–2400 ova. No testicular vesicles were visible before October but spermatozoa were present in November and December. Spawning in each of three years occurred in November (4th to 6th nights after full moon) simultaneously with mass spawning of scleractinian corals. The buoyant eggs (along with sperm in the hermaphroditic zooids) were released in bundles. Some large oocytes and mature sperm were still present in December.     

Acid stress in respect to calcium and magnesium concentrations in the plasma of perch during maturation and spawning

Synopsis Plasma calcium and magnesium concentrations in perch,Perca fluviatilis, were monitored in an acid lake, Lake Iso Tenhetty (pH ∼5, Al concentrations 0.3–0.5 mg l^-1) compared with a nearby reference lake, Lake P?ij?nne, in Southern Finland. The effect of acid stress could be noticed as 1/3 lower fecundity of perch in the acid lake. Plasma Ca concentrations were temporarily lower in the middle of the winter in the fish of the acid lake, and in April–May samples the situation was opposite. Plasma Mg concentration was also lower in the perch from the acid lake in midwinter months, when compared with the double as high values (∼3 mmol l^-1) from the reference lake. Elevated level of plasma Mg have been reported for fish in cold acclimation especially in winter. Thus overwintering may be specially stressing for some specimens in acid waters. Also ova did contain clearly less magnesium in the midwinter sample from the acid lake perch compared with the reference lake sample. This difference, however, was no more to be found later in spring. Mg content in the ova of perch was in both cases high, which may be necessary to the breeding in comparable acid waters. According to the literature fish cannot increase their magnesium content directly from the water. Mortality for the reference lake embryos was lower than those of the acid lake when incubated in the acid lake. No physiological acclimation inside the fish could be demonstrated in this case.     

Multispecies spawning sites for fishes on a low‐latitude coral reef: spatial and temporal patterns

Spawning sites used by one or more species were located by intensively searching nearshore coral reefs of Kimbe Bay (New Britain, Papua New Guinea). Once identified, the spawning sites were surveyed repeatedly within fixed 5 m radius circular areas, for > 2000 h of observations ranging from before dawn to after dusk spanning 190 days between July 2001 and May 2004. A total of 38 spawning sites were identified on the seven study reefs distributed at an average of one site every 60 m of reef edge. Pelagic spawning was observed in 41 fish species from six families. On three intensively studied reefs, all 17 spawning sites identified were used by at least three species, with a maximum of 30 different species observed spawning at a single site. Spawning was observed during every month of the study, on all days of the lunar month, at all states of the tide and at most hours of the day studied. Nevertheless, the majority of species were observed spawning on proportionately more days from December to April, on more days around the new moon and in association with higher tides. The strongest temporal association, however, was with species‐specific diel spawning times spanning < 3 h for most species. While dawn spawning, afternoon spawning and dusk spawning species were differentiated, the time of spawning for the striated surgeonfish Ctenochaetus striatus also differed significantly among sites. The large number of species spawning at the same restricted locations during predictable times suggests that these sites are extremely important on this low‐latitude coral reef.     

Locomotor activity of river lamprey Lampetra fluviatilis (L.) during the spawning season

At high latitudes (62–64°N) the river lamprey Lampetra fluviatilis (L.) is shown to have a 24-hr locomotor activity during its spawning period just before midsummer. By keeping lampreys in cold water, the spawning was delayed about one month. Analysis of event recorder graphs indicate that the 24-hr activity is caused by addition of diurnal spawning activity to the basic nocturnal activity and is not caused by weak Zeitgeber conditions during midsummer.Water temperature might indirectly determine time of spawning of the river lamprey.     

Patches and the responses of lake benthos to sunfish nest-building

Summary Males of three sunfish species (Centrarchidae) construct nests for spawning and often share them sequentially in the littoral zone of a 4-hectare lake in New York State. To determine spatial and temporal effects of this reproductive behavior on zoobenthos in patches, I sampled bottom assemblages from inside nests and from adjacent (<1 m from nest perimeter), relatively undisturbed sites during the reproductive season of 1986 and immediately prior to nest-building in 1987. The reproductive behaviors of largemouth bass (Micropterus salmoides), redbreast sunfish (Lepomis auritus), and pumpkinseeds (L. gibbosus) altered relative abundances and significantly decreased benthic invertebrate diversity and density. These effects were extremely pronounced during the reproductive season and were partially detectable the following year. Community changes were probably the result of both bioturbation (modification of sediment size and organic content) and predation. The ecosystem-wide effects of nest-building are evaluated in terms of the number, distribution, and longevity of patches.     

High-quality seed dispersal by fruit-eating fishes in Amazonian floodplain habitats

Seed dispersal is a critical stage in the life history of plants. It determines the initial pattern of juvenile distribution, and can influence community dynamics and the evolutionary trajectories of individual species. Vertebrate frugivores are the primary vector of seed dispersal in tropical forests; however, most studies of seed dispersal focus on birds, bats and monkeys. Nevertheless, South America harbors at least 200 species of frugivorous fishes, which move into temporarily flooded habitats during lengthy flood seasons and consume fruits that fall into the water; and yet, we know remarkably little about the quality of seed dispersal they effect. We investigated the seed dispersal activities of two species of large-bodied, commercially important fishes (Colossoma macropomum and Piaractus brachypomus, Characidae) over 3 years in Pacaya-Samiria National Reserve (Peru). We assessed the diet of these fishes during the flood season, conducted germination trials with seeds collected from digestive tracts, and quantified fruit availability. In the laboratory, we fed fruits to captive Colossoma, quantified the proportion of seeds defecated by adult and juvenile fish, and used these seeds in additional germination experiments. Our results indicate that Colossoma and Piaractus disperse large quantities of seeds from up to 35% of the trees and lianas that fruit during the flood season. Additionally, these seeds can germinate after floodwaters recede. Overexploitation has reduced the abundance of our focal fish species, as well as changed the age structure of populations. Moreover, older fish are more effective seed dispersers than smaller, juvenile fish. Overfishing, therefore, likely selects for the poorest seed dispersers, thus disrupting an ancient interaction between seeds and their dispersal agents. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Kleptoparasitism of freshwater crabs by cichlid fishes endemic to Lake Barombi Mbo,Cameroon, West Africa

Synopsis Although kleptoparasitism, or food-stealing, is common in birds and some carnivorous mammals, reported instances are exceedingly rare in fishes. We studied the behaviour and ecology of the 11 endemic tilapiine cichlids of Lake Barombi Mbo, Cameroon, West Africa. Here we report that six of the Barombi cichlids (Stomatepia mariae, S. pindu, Konia eisentrauti, Pungu maclareni, Sarotherodon lohbergeri, andS. linnellii) kleptoparasitize freshwater crabsPotamon africanus.     

Bacteriocin-like inhibitor substances produced by Mexican strains of Bacillus thuringiensis

Bacteriocins are antimicrobial peptides synthesized and secreted by bacteria and could potentially be used as natural food preservatives. Here, we report the production of bacteriocin-like inhibitor substances (Bt-BLIS) by five Mexican strains of Bacillus thuringiensis. Bacillus thuringiensis subsp. morrisoni (LBIT 269), B. thuringiensis subsp. kurstaki (LBIT 287), B. thuringiensis subsp kenyae (LBIT 404), B. thuringiensis subsp. entomocidus (LBIT 420) and B. thuringiensis subsp. tolworthi (LBIT 524) produced proteinaceous Bt-BLIS with high levels of activity against Bacillus cereus and other gram-positive bacteria. Although none was active against the gram-negative bacteria, Escherichia coli, Shigella species and Pseudomonas aeruginosa, the five Bt-BLIS demonstrated antimicrobial activity against Vibrio cholerae, the etiologic agent of cholera. Biochemical and biophysical studies demonstrated that the five Bt-BLIS could be categorized into two groups, those produced by LBIT 269 and 287 (Group A) and LBIT 404, 420, 524 (Group B), based on relative time of peptide synthesis, distinctive bacterial target specificity and stability in a wide range of temperatures and pH. Because of their stability and bactericidal activities against B. cereus and V. cholerae agents of emetic, diarrheal and lethal syndromes in humans, these Bt-BLIS could potentially be used as biodegradable preservatives in the food industry.     

Trophic relationships and seasonal utilization of salt-marsh creeks by zooplanktivorous fishes

Synopsis In a high salinity estuary at North Inlet, South Carolina, co-occurrence and possible competition among adults of four dominant zooplanktivorous fishes were minimized by seasonal adjustments in lateral and vertical distributions as well as in dietary preferences. In winter, Atlantic silversides, Menidia menidia, occupied the entire water column while other planktivores were rare or absent from the estuary, and they consumed large prey such as mysid shrimps and fish larvae. An immigration of bay anchovies, Anchoa mitchilli, in the spring resulted in a redistribution of species with Atlantic silversides shifting to the surface waters and bay anchovies dominating the lower half of the water column. Both fishes consumed mostly copepods in the spring, but each favored a different species. There was little similarity in the large prey items consumed by the two fishes. Striped anchovies, Anchoa hepsetus, arrived in mid-summer and were most abundant at the surface while bay anchovies continued to dominate the bottom waters. Atlantic silversides were rare in all summer collections. The diets of the two anchovies were similar, but vertical separation during the period of maximum zooplankton abundance probably minimized competition. Rough silversides, Membras martinica, which were obligate surface dwellers, shared the upper water column with striped anchovies, but the two species had very different diets during their period of co-occurrence. Although seasonal changes in fish diets reflected shifts in zooplankton composition and all fishes consumed a variety of prey types, preferences for some prey taxa and total avoidance of others were indicated. Electivity indices indicated an especially strong selection for fiddler crab megalopae by all fishes in the summer and fall. All fishes, except rough silversides, which fed almost exclusively on copepods and crab zoeae, consumed large prey items when they were available. Fine scale partitioning of the food resources was apparent in the selection of different copepod and insect species by the fishes. Spatial and temporal separation in the distribution and/or dietary preferences of the zooplanktivores fishes probably reduces the potential for resource competition. Given the high abundances and selectivity of the planktivores, significant impacts on some zooplankton populations probably result.     

Synchronous spawning in a recently established population of the zebra mussel,Dreissena polymorpha,in western Lake Erie,USA

Seasonal patterns of reproduction in a newly established population of Dreissena polymorpha are described for a site in the western basin of Lake Erie. Reproduction was monitored by histological examination of gonads, analysis of shell length-dry weight relationships, and following abundance of planktonic and settling larvae. Patterns of planktonic larval abundance and settling showed a distinct bimodal pattern in July and August, but conflicted with histological and length-dry weight data that showed spawning was a brief, highly synchronous event occurring in late August. Differences between histological data and abundance of larvae in the plankton can be explained as resulting from drift of larvae from disjunct populations of D. polymorpha which spawned earlier, into the study area. Veliger larvae were present in the plankton at low densities throughout the warm months before and after periods of peak abundances. The presence of these larvae can be explained by a combination of asynchronous spawning among local populations and postponed settlement by planktonic larvae.