Elevated summer temperatures delay spawning and reduce redd construction for resident brook trout (Salvelinus fontinalis)

Redd (nest) surveys for resident brook trout (Salvelinus fontinalis) were conducted annually in a mountain lake in northern New York for 11 years with multiple surveys conducted during the spawning season in eight of those years. Repeated surveys throughout the spawning season allowed us to fit an individually based parametric model and estimate the day of year on which spawning was initiated, reached its midpoint, and ended during each year. Spawning phenology was then assessed relative to (1) mean of maximum daily air temperature and (2) mean of maximum daily water temperature at the lake bottom during summer in each year using a linear model. Elevated temperatures in summer were correlated with a delay in spawning and a reduction in the total number of redds constructed. Increasing the summer mean of maximum daily air temperatures by 1 °C delayed spawning by approximately 1 week and decreased the total number of redds constructed by nearly 65. Lake spawning brook trout select redd sites based on the presence of discharging groundwater that is relatively constant in temperature within and across years, leading to relatively consistent egg incubation times. Therefore, delayed spawning is likely to delay fry emergence, which could influence emergence synchrony with prey items. This work highlights non‐lethal and sub‐lethal effects of elevated summer temperatures on native resident salmonids in aquatic environments with limited thermal refugia.     

Post-settlement mortality and growth of newly settled reef corals in a subtropical environment

There are few studies of post-settlement mortality of newly settled corals, particularly on subtropical reefs. This study examined the mortality and growth of spat of three broadcast spawning coral species at the Solitary Islands, eastern Australia (30°S). Mortality of spat was high, with only 0.2–2.8% surviving their first year of life. Growth was slow, with coral spat achieving a maximum diameter of 2 mm after 8 months. High post-settlement mortality and slow growth rates are likely to contribute to low rates of recruitment of broadcast spawning species at the Solitary Islands.     

Reproduction, population dynamics, growth and production ofScrobicularia plana da costa (pelecypoda) in the Bidasoa estuary, Spain

The breeding cycle, recruitment, population dynamics, growth and production ofScrobicularia plana were studied at one station in the Bidasoa estuary (SE of the Biscay Bay, Spain) during a period of 3 or 4 years. To complete this study, the reproduction for a period of 1 year was analysed at two other sites of the estuary. At none of the stations important differences in spawning activity were observed between the different years. The animals reproduced for the first time when they reached the age of two years. The histological data and the recruitment analysis showed only one spawning period between June and mid-September, with a peak in July-August. This breeding pattern differs from those shown by other southern European populations. The recruitment of spat (0.25–0.50 mm) occurred from June–July to October–December in different years. The population showed different annual patterns of density and population structure, depending on recruitment success. Growth was most rapid in spring and summer. The bivalves reached a mean length of 21.8 mm at the age of approximately 16 months; in the following year they grew to 30 mm. The growth during the life span fitted the theoretical growth equation of Von Bertalanffy. Annual production was in the range of 59.0–83.4 g AFDW m^–2 year^–1. The P/B ratios of the population varied between 0.84 and 1.48 (1.06 ± 1.36; ¯x ± 95% C.I.).     

Aspects of the spawning biology of the Brazilian sardine, Sardinella brasiliensis (Steindachner, 1879), (Clupeidae)

Biological data, size frequency distribution of intraovarian oocytes, maturity indices and histological observations of the gonads were used to assess the spawning cycle of S. brasiliensis , sampled September 1981–August 1982 throughout the main fishing area off the Brazilian coast (22°S to 28°S). Post-ovulatory follicles are described and classified, and the incidence of mature females displaying these structures was calculated. The main findings were (a) spawning occurred during the spring and summer with a maximum in December and January; (b) spawning occurred throughout the area studied; (c) spawning was fractional; (d) average batch fecundity was 26 000 oocytes per female, or 393 eggs g⁻¹; (e) spawning frequency reached values of approximately 50% during the spawning peak, but was sensibly lower during the other months of spawning activity.     

Effect of seawater temperature on reproductive seasonality and fecundity of Pseudoplexaura porosa (Cnidaria: Octocorallia): latitudinal variation in Caribbean gorgonian reproduction

Abstract. The majority of tagged colonies of Pseudoplexaura porosa in Bermuda were reproductive over 2 months in the summer. They spawned 5–8 d after the full moon, with a peak on the sixth day, similar to colonies in Panama. The months of spawning were August and September in 1998, but July and August in 1999 and 2000. This temporal difference between the months of spawning corresponded to inter-annual variations in seawater temperature profiles. Initial gamete development each year occurred only when the daily mean seawater temperature during the month before spawning exceeded 27°C. There was a significant positive relationship between reproductive effort (gamete volume) of colonies and rising seawater temperature in the month preceding spawning; this was true for both the initial and the second spawning months. The end of the reproductive season each year was triggered by the decline in seawater temperature past the summer maximum. The duration of the reproductive season of conspecifics at the central Caribbean reef of Panama is 2 months longer than in Bermuda. This can be explained by the smaller annual temperature range at the lower latitude and the earlier onset of temperatures favorable for gamete development. Fecundity estimates for members of P. porosa (mean oocyte and spermary densities) in Bermuda were lower than for conspecifics in Panama. The shorter reproductive season in Bermuda, in addition to the lower fecundity of colonies, indicates that reproduction in P. porosa is compromised at this high latitude reef.     

NATURAL SETTLEMENT AND EARLY GROWTH OF SPAT OF THE QUEEN SCALLOP CHLAMYS OPERCULARIS (L.), WITH REFERENCE TO THE FORMATION OF THE FIRST GROWTH RING

The settlement and early growth of spat of Chlamys opercularis(L.) on benthic epifauna has been studied. Intensity of spatsettlement may not always correspond to intensity of spawningand the minor summer spawning may be of greater importance thanthe more intensive autumn spawning. The growth rates of spatwere estimated from analysis of size frequency data and thenature of the first growth ring has been studied with referenceto the bimodality in size range and the relationship with thetwo peaks of settlement.     

Timing of spawning and glochidial release in Scottish freshwater pearl mussel (Margaritifera margaritifera) populations

1. The timing of reproduction was investigated in six Scottish freshwater pearl mussel populations from 1993 to 2002. Gravid females were examined and the release of mussel larvae (glochidia) was monitored. 2. Annual spawning (oviposition) and spat (glochidial release) events occurred during June to July and June to September, respectively. 3. Between‐river differences in timing seem to be related to water temperature. Mussels in the warmest rivers tend to spawn and spat first, and vice‐versa. 4. Thermal variations also seem to influence the timing of reproduction within rivers, which can be delayed by several weeks during cold years. At least 3000°‐days occur between annual episodes of glochidial release. 5. The timing of spawning is determined gradually, probably by a thermal summation effect. 6. The release stage occurs as a sudden, synchronised event, with most of the glochidia spat over 1–2 days, indicating that it is triggered by an environmental cue. Sudden changes in water temperature and/or river level often result in spats, and the underlying mechanism may be respiratory.     

Observations on the biology and seasonal variation in feeding of the east coast round herring Etrumeus wongratanai (Clupeiformes), off Scottburgh,KwaZulu-Natal,South Africa

The basic biology and ecology of the South African east coast round herring Etrumeus wongratanai was investigated from samples of fish collected between 2013 and 2016. This species is short-lived and reaches a maximum of 3 years of age, with rapid growth in its first year of life. It reproduces from June to December (austral summer) and condition factor was lowest in May through to August and increased from September, probably reflecting the physiological strain before and during spawning. Fish larvae were the most important food items consumed during summer, whereas eucalanid copepods were the most important prey at other times of the year. Stable-isotope data suggest that there are gradual changes in the trophic level with increasing fish size, δ¹⁵N and δ¹³C values also differed between seasons. The results obtained here are compared with those of other Etrumeus species, regionally and globally.     

Macroscopic and histological analyses of gonads during the spawning season of Chionodraco hamatus (Pisces,Channichthyidae) off Terra Nova Bay,Ross Sea,Southern Ocean

A macroscopic and histological analysis of gonads was carried out during the spawning season of the high-Antarctic channichthyid Chionodraco hamatus in the western Ross Sea. Samples were collected between December and February during several years in the coastal waters of Terra Nova Bay. Gonad maturity stages were described for males and females according to macroscopic and histological scales. Using multi-year data, the estimated length at first spawning of females was about 35 cm TL, very similar to that obtained indirectly for males. Similar to many other high-Antarctic fish, C. hamatus is a summer spawner. The greater part of the stock was indeed in spawning condition between December and February, although a large proportion of females large enough to spawn probably did not spawn in that season. The present data confirm that C. hamatus, as is typical for Antarctic fish, probably spawns a single batch of oocytes once a year. In addition, vitellogenesis is a slow process that extends over at least 1 year. Discrepancies between the macroscopic and histological appearance of gonads were found. These were associated mainly with spent and resting females (maturity stages 5 and 2, respectively). This study demonstrates the importance of histological analysis of gonads in order to confirm the results of the macroscopic analyses routinely carried out in studies of reproductive biology. This is of particular importance in determining size at maturity and spawning stock biomass, for assessment purposes.     

The link between migration, the reproductive cycle and condition of Sardinella aurita off Mauritania, north-west Africa

The annual migration pattern of round sardinella Sardinella aurita up and down the north-western African coast between 12° N (Senegal) and 22° N (western Sahara) was shown to be associated with spawning activity and a distinct seasonality in fish condition, based on monthly sampling from commercial catches (2000–2003). Some S. aurita were found to spawn throughout the entire year, but a peak in spawning existed during the summer (June to September). The spawning cycle is apparent from seasonality in maturity stages, but is also demonstrated by the increase in gonad mass and fat content of the fish in springtime, the period preceding spawning. During the months after spawning, although feeding is maintained, the physical condition of the fish collapses, and fat content rapidly declines.     

Modeling and predicting potential spawning habitat of anchovy (Engraulis encrasicolus) and round sardinella (Sardinella aurita) based on satellite environmental information

Anchovy and round sardinella are two important small pelagic species in the Mediterranean that spawn during the summer period. This is a first attempt to model and predict the two species’ potential spawning habitats in this area. Generalized additive models (GAMs) were constructed based on satellite environmental variables and presence/absence egg data, available from ichthyoplankton surveys conducted in the North Aegean Sea during early summer (June 2003–2006). These models were subsequently used to predict the probability of anchovy and round sardinella spawning in the Greek Seas as well as the entire Mediterranean and Black Sea during the same month of the year. The interaction of bottom depth and chlorophyll explained most of the deviance in the presence/absence GAMs of both species, indicating spawning over continental shelf areas with increased surface chlorophyll values. Round sardinella spawned closer to coast than anchovy. Predicted potential spawning areas for anchovy and round sardinella in unsampled areas of the Greek Seas and the entire Mediterranean and Black Sea were in good agreement with existing information on the distribution and extent of the spawning grounds, especially for anchovy. Modeling the species’ reproductive activity in relation to easily accessible environmental information and applying the models in a predictive way could be an initial, low-cost step to designate potential spawning fish habitats. Guest editor: V. D. Valavanis Essential Fish Habitat Mapping in the Mediterranean     

Reproduction of the summer flounder, Paralichthys dentatus (L.)

The reproduction of summer flounder, Paralichthys dentatus (L.), occurring in the Middle Atlantic Bight was studied from 1974–1979. Males dominated the length interval between 21–35 cm t.l. and were essentially absent in samples >55 cm t.l. Females were more abundant in all length intervals >45 cm t.l. Length at maturity ranged from 24–27 cm t.l. for males and from 30–33 cm t.l. for females which coincided with length at age two. Ovarian egg diamerter frequencies indicated summer flounders are serial spawners and the trend in mean and maximum maturity indexes (% ovary weight of total fish weight) indicated spawning began in September and continued through February in 1975 and probably into March in 1976. Annual condition cycle of males peaked in September and was lowest in April while females' cycle reached a maximum in October which coincided with peak spawning time. Fecundity was related to length, weight and ovary weight for 1974–1977 and the length-fecundity equation F = 0.0007975 L ^3.402 was found to be the best predictive relationship. The overall reproductive strategy of summer flounder was discussed and apparently tends to maximize reproductive potential through an extended spawning season, early maturation, high fecundity, serial spawning and extensive spawning migrations.     

Sexual reproduction in the tropical corallimorpharian Rhodactis rhodostoma

Abstract. Polyps of the tropical corallimorpharian Rhodactis rhodostoma segregate sexes between center and edge positions within aggregations produced by clonal replication. On a reef flat at Eilat, northern Red Sea, infertile polyps and males occur mainly along the edges of clonal aggregations, while females mostly occupy central positions within each aggregation. In addition, on the inner to middle reef flat where polyps of this species are abundant, aggregations consist mostly of females. On the outer reef flat, where polyps are rare, a sampled aggregation consisted mostly of males and infertile polyps. Male polyps are significantly smaller than females, and the smallest polyps are infertile. Fecundity increases significantly with polyp size in females, but testis size and number do not vary with body size in males. Oocytes are present in polyps during most of the year and gradually increase in size until annual spawning in June-July during the period of maximum day length. Testes do not vary significantly in size during the year and remain a small proportion of body mass (>8%). In contrast, females invest up to 30% of their body mass into gonads during the months immediately before spawning. The annual spawning of gametes coincides with a temporary drop in the frequency of clonal replication by polyps. We estimate that each female polyp of R. rhodostoma may release up to 3000 large eggs (500 μm in maximum diameter) each summer. The high investment of this corallimorpharian in sexual production of planktonic propagules may allow rapid dispersal to reef habitats distant from parent populations.     

Age and growth of a colonizing minnow,Barbus anoplus,in a man-made lake in South Africa

Synopsis Aspects of the life history of Barbus anoplus were studied in Lake le Roux, a turbid man-made lake on the Orange River, South Africa. This minnow underwent a population explosion and successfully colonized the shoreline of the newly-formed lake during the early phases of reservoir filling. Male and female B. anoplus reach sexual maturity in one year at about 40 mm fork length. They have a multiple spawning habit with the first spawning in November–January and the second in February–March. The growth of the two resulting cohorts is discussed. It is proposed that the offspring from the second spawning not only acts as a ‘back-up’ but is capable of prolonging the life of that year-class into an additional reproductive season. Most of the minnows die after their second summer, but more offspring from the second spawning, especially females, live into a third summer. Females attain a larger maximum size (73 mm FL) and age (3–4 years) than males (60 mm FL, 2–3 years). B. anoplus is small and short-lived with a high seasonal reproductive potential, which is in contrast to the larger Barbus species in the Orange River system. These life-history traits enable the species to colonize and successfully inhabit unstable environments and probably account for its widespread distribution.     

Annual gonadal cycle and reproduction in Patagonotothen tessellata (Richardson 1845 (Nototheniidae: Pisces) from the Beagle Channel, Argentina

The reproductive biology of Patagonotothen tessellata (Richardson 1845) in the Beagle Channel, Tierra del Fuego, Argentina was analysed from weekly captures over a 3-year period (1987–1989). The spawning periods and lengths thereof were analysed using GSI curves and monthly percentage distributions of maturation stages. Two gonadal maturation cycles and two spawning periods (winter and summer) within 1 year were defined. Also discussed is whether the same specimens are able to mate successfully in winter and summer, and whether the reproductive effort varies between the seasons. Male parental behaviour and the likely consequences on their energy levels are considered.     

Reproductive and growth strategies of the red roach, Rutilus arcasii (Steindachner, 1866), in two contrasting tributaries of the River Duero, Spain

The life-histories of red roach were assessed in the R. Moros and the R. Ucero, two contrasting tributaries of the R. Duero. Growth occurred from April to October and Ucero red roach were larger than those in the Moros from their second year onwards. Condition increased with gonad development and abruptly decreased after spawning in both populations. The condition of Ucero fish recovered during the summer, but that of the Moros fish remained low. The same year classes (1980 and 1982) dominated both populations. River Moros red roach spawned in a 4-week period between the end of April and early June, while the spawning season of Ucero red roach lasted until August. The length to fecundity relationship was similar for both populations, and fecundity and ovum size increased with fish length. The life-history traits of these red roach populations are discussed in relation to current life-history theories.     

Age estimation,growth and maturity of the Argentine hake (Merluccius hubbsi Marini, 1933) along the northernmost limit of its distribution in the south-western Atlantic

Age, growth and length-at-maturity of the Argentine hake (Merluccius hubbsi) were studied in the northernmost limit of the species distribution in the south-western Atlantic. A total of 351 otoliths and information from 1610 specimens sampled from the industrial double-rig trawl landings between May 2013 and April 2014 were used. Age and growth were estimated by counting and measuring increments in sectioned sagittae otoliths, and length at maturity was estimated based on macroscopic gonadal analysis. For both sexes, hepatosomatic index and condition index increased mainly during spring, reaching a maximum at the end of summer before the subsequent spawning season began. Gonadosomatic index was highest in April, believed to correspond with peak spawning. The annual periodicity of alternate opaque and translucent zones was validated by marginal increment analysis. Growth curves were fitted to back-calculated size at age by fitting the three-parameters von Bertalanffy growth function. The maximum age was 5 years in fish of either sex. Females attained larger sizes than males. The parameters of the von Bertalanffy growth equations were: L∞?=?533?mm, k?=?0.231 year^?1 and t₀?=??0.935 year for females; L∞?=?394?mm, k?=?0.405 year^?1 and t₀?=??0.463 year for males. The mean length and age at first maturity was 273?mm at 1.9 years for males and 274?mm at 2.0 years for females.     

Effects of compressed seasonally changing day-length cycles on spawning performance, production of viable eggs and levels of vitellogenin in plasma in female yellowtail snapper Lutjanus argentiventris

Reproduction in yellowtail snapper Lutjanus argentiventris took place after compressing the seasonally changing day length into a 3 month period applied during two consecutive winters, with the longest and shortest days in December and February, respectively. During the first winter, there was no clear peak of days of spawning and the production of viable eggs was similar from the longest and throughout the decreasing day lengths until reproduction ceased. The level of plasma vitellogenin rose abruptly to a maximum concentration during the increasing day length and then decreased dramatically before the longest day length. During the second winter, a clear peak in the number of days of spawning and the highest production of viable eggs occurred around the longest day length. These results showed that it is feasible to synchronize day length between winter-induced and natural summer and autumn reproduction to produce eggs and larvae during the year.     

Influence of environmental conditions on the ovarian cycle and serum chemistry of Cyprinus carpio in the Dal lake, Kashmir (India)

SUMMARY 1. The study presents adaptive and acclimatory changes observed in Cyprinus carpio communis L with respect to ovarian cycle and serum levels of electrolytes, calcium, total proteins and albumin as a consequence of wide temperature and sunshine variation in the natural environment of Dal lake in Srinagar, Kashmir (India).
2. The atmospheric temperatures in Srinagar show well-defined seasonal and diurnal variations. During the period of study, the mean monthly average temperature in summer (June-August) was 24°C whereas in winter (December-February) it fell to 3.6°C. The total hours of sunshine during the winter months were about half of those found in summer.
3. Under local thermal and photo conditions the fish was found to spawn once a year compared to biannual spawning in tropical chmates.
4. A significant decrease was found in serum sodium, potassium and chloride concentrations during the months of January and February when the mean minimum atmospheric temperatures reached −2.5°C and −l.2°C respectively.
5. The serum calcium levels showed a marked increase during the period corresponding to ovarian maturity and spawning of fish.
6. A significant rise in total serum protein concentration was induced by decreased environmental temperatures. Serum albumin levels were found to exhibit a sharp fall coinciding with the spawning period.     

The Effects of Water Temperature on the Timing of Spawning and Spat Settlement of the Yesso Scallop (Mizuhopecten yessoensis Jay, 1857) in Minonosok Cove (Posyet Bay,Peter the Great Bay,Sea of Japan)

Russian Journal of Marine Biology - The effect of water temperature on the timing of spawning and spat settlement of the Yesso scallop (Mizuhopecten (=Patinopecten) yessoensis Jay, 1857) in...