Maturity and spawning pattern of Sardinella aurita in relation to water temperature and zooplankton abundance off Ghana, West Africa

Studies on the maturity and spawning pattern of Sardinella aurita Valenciennes in relation to sea surface temperature (SST) and zooplankton abundance were carried out during the period 1986–91 in Ghanaian waters (West Africa). Both sexes exhibited synchronous seasonal maturation patterns. The mean length at first maturity occurred at approximately16.7 cm for males and 17.1 cm for females. The mean length at first maturity (L₅₀) increased in comparison with that observed in the 1970s. Three spawning seasons were identified: a major season which extends from July to October, and two minor seasons which occur in March and December. Significant correlations were found between the female gonadosomatic index and SST, between egg abundance and SST, and between egg abundance and zooplankton abundance. The SST seems to be an important factor in species maturation. There is a time lag between attainment of peak gonad maturation and onset of spawning. Spawning appears to commence in response to the start of the coastal upwelling which is characterised by a sharp decrease in SST and an increase in zooplankton abundance.     

Multivariate analyses of the biometric features from Philippine sardines – implications for the phylogenetic relationships of the freshwater Sardinella tawilis (Teleostei,Clupeomorpha)*

Philippine sardines are members of the commercially important Sardinella genus (Family Clupeidae). Sardines are mostly marine species with a very few exception like the Philippine freshwater sardine, Sardinella tawilis, of Lake Taal. This species is believed to have immigrated from Balayan Bay some 250 years ago. To determine the relationship of freshwater S. tawilis to the marine forms, 35 biometric features were investigated. The variables were subjected to univariate (mean, standard deviation and coefficient of variance) and multivariate analyses [Principal Component Analysis (PCA) and Hierarchical Cluster Analysis]. Results from univariate tests revealed that the number of ventral fin ray can discriminate Sardinella lemuru from the rest of the sardines. Multivariate PCA, on the other hand, showed discrete separation of the marine sardines. Sardinella tawilis, however, cannot be clearly separated from the marine species, Sardinella albella. The same clustering was recovered in HCA, thus providing evidence that S. albella is the closest marine relative of the freshwater S. tawilis.     

Sexuality, sex change and maturation patterns in the yellowfin seabream, Acanthopagrus latus (Teleostei: Sparidae) (Houttuyn, 1782)

Macroscopic and histological studies were carried out to describe the reproductive styles and sex reversal and to follow gonadal changes in captive yellowfin seabream during the second year of life. Four reproductive styles are found in Acanthopagrus latus (Houttuyn, 1782): (i) males and females (gonochorism), (ii) functional males, (iii) transitionals and (iv) functional females. The species is a protandric hermaphrodite and begins life as a functional male with testicular zone undergoing active spermatogenesis, while the ovarian zone is arrested at the primary growth (perinucleolar) phase. Males and females were encountered in virtually all size‐classes. Functional males outnumbered the functional females in all size‐classes in which they were encountered. Sex reversal begins in the transitionals from July to August, after spawning in the functional males, at 14.9–20.2 cm standard length (SL) and, by November, maturation of the ovarian tissue begins. A. latus in cages in Kuwait waters spawns from January to April with a peak in February for males, and a peak in March for females and transitionals. Spawning begins in the 18.3–20.2 cm size‐range fish, peaking in the 20.3–22.2 cm size‐range in both males and females and also in the transitionals, although a few of the latter spawn from 14.9 cm SL. In relation to age, spawning begins at 20 months in males and peaks at 21 months. Females begin to spawn at 21 months with a peak at 22 months, while transitionals generally begin to spawn at 20 months, although a few 14–15‐month‐old sex‐changing individuals were encountered. Temperature, either alone or in combination with other unknown factors, triggers spawning in A. latus.     

Reproductive biology ofAwaous guamensis, an amphidromous Hawaiian goby

Synopsis Spawning season, size at first reproduction, oocyte maturation, and fecundity ofAwaous guamensis, an amphidromous Hawaiian goby, were studied from June 1989 through May 1991 in the Wainiha River, Kau'ai, Hawai'i. Female fish larger than 73 mm standard length (SL) had mature gonads from August through December in 1989 and 1990. Gonadosomatic index (GSI) values for mature females ranged from 0.2 to 14.5 during the spawning season. Male fish larger than 64 mm SL had elevated GSI values from June 1989 through December 1989 and from August 1990 through December 1990. Mature sperm were found in two male fish collected in January and February. GSI values for mature males ranged from less than 0.01 to 4.0 in the spawning season. Size-frequency distributions of measurements of vitellogenic oocyte diameters and microscopic observations of oocytes indicated this species has group-synchronous oocyte development. Ovarian maturation stages examined over a 29-month period suggest that members of the stock spawned at different times within the spawning season, although mass spawning events have been documented for this species. Estimates of clutch sizes from nests measured in situ were comparable to estimates of potential fecundity from in vitro examination of ovaries, and indicated that female fish deposited an entire clutch during a spawning event. No evidence for multiple spawning by an individual fish in a single season was found. However, microscopic observations of brown bodies in some ovaries suggested that individual fish probably spawn more than once in a lifetime.     

Reproductive cycle of gilt sardine,Sardinella aurita,Valenciennes 1847, in the eastern middle Adriatic Sea

The annual reproduction cycle of gilt sardine, Sardinella aurita, based on gonad maturity stages, gonad weight and gonadosomatic index was the subject of this study. A total of 2033 gilt sardines (983 males, 1021 females and 29 undetermined) were analysed. Fish were collected monthly from commercial purse seiners between November 2007 and January 2009 in the eastern middle Adriatic Sea (mesh size 8 mm/bar length/; sampling: five boats per month). Based on the monthly evolution of gonad maturation stages, gonad weights and gonadosomatic index, the peak spawning season was determined to be from June to August. Variations in sea surface temperature (SST) coincided with monthly variations of the gonadosomatic index. Highest monthly average values for both analysed parameters were recorded in July (GSI = 3.38; T = 26.5°C). Fifty per cent (L₅₀) of males and females reached sexual maturity at TL 15.8 cm and at 16.6 cm, respectively. Absolute fecundity ranged from 8458 to 48 032 (mean 34 565 ± 10 310), whereas relative fecundity was from 171 to 722 (mean 385 ± 104.35). Mean value of the oocyte size was 0.53 ± 0.10 mm.     

Reproductive activity in the commercially exploited mediterranean muricid <Emphasis Type="Italic">Hexaplex trunculus</Emphasis> collected from Boughrara lagoon (Southern Tunisia)

The banded murex Hexaplex trunculus (Linnaeus, 1758) is a commercially exploited gastropod in the Mediterranean region including Tunisia where it has become an important fishery resource these last years. In the present investigation, some reproductive aspects of this species were described in the population of Boughrara lagoon based on macroscopic examination of the gonads (gonadic conditional indices) together with observation of the seasonal hypertrophy of the penis in males and capsule gland in females. This procedure of assessing reproductive activity was validated by field observations of copulation and spawning. Mature females were found during 10 months and mature males during 8 months being both frequent in January and February. Reproductive activity was slightly asynchronous between sexes with males reaching maturity before females. Gonadic release occurred earlier in males between January and March against February to April in females. These findings were in agreement with field observations of copulation in January and February and egg-capsule laying in late February and March. Hatching juveniles were observed in the field in April and May.     

Reproductive biology of the silver pomfret, Pampus argenteus (Euphrasen), in Kuwait waters

The reproductive activities of the silver pomfret, Pampus argenteus (Euphrasen), in Kuwait waters were investigated from March 1996 to February 1998. Observations on the seasonal distribution of maturity stages and variations in seasonal fluctuations in the gonadosomatic index (GSI) confirmed recent findings that the spawning period begins in May. The species has a prolonged spawning period in the females extending from May to August, whereas the males mature in April and ripe specimens were encountered in monthly samples until September. The recruitment pattern confirmed the one breeding season. There are two spawning peaks, the first in May and the second in August. Variations in GSI relative to fish length indicated that females and males are most fecund at about 24.5–26.4 cm and 20.5–22.4 cm length classes, respectively. The males mature earlier than females, at a minimum size of 12.5–14.4 cm, while the females mature at 20.5–22.4 cm. The oocyte diameter‐frequency distribution suggests a serial rhythm of spawning. Fecundity ranged from 28 965 to 455 661 and correlated positively with: (a) standard length (P < 0.006); (b) ovary weight (P < 0.001); and (c) body weight (P < 0.001), and negatively with egg size (P < 0.003).     

Hidden Diversity in Sardines: Genetic and Morphological Evidence for Cryptic Species in the Goldstripe Sardinella,Sardinella gibbosa (Bleeker, 1849)

Cryptic species continue to be uncovered in many fish taxa, posing challenges for fisheries conservation and management. In Sardinella gibbosa, previous investigations revealed subtle intra-species variations, resulting in numerous synonyms and a controversial taxonomy for this sardine. Here, we tested for cryptic diversity within S. gibbosa using genetic data from two mitochondrial and one nuclear gene regions of 248 individuals of S. gibbosa, collected from eight locations across the Philippine archipelago. Deep genetic divergence and subsequent clustering was consistent across both mitochondrial and nuclear markers. Clade distribution is geographically limited: Clade 1 is widely distributed in the central Philippines, while Clade 2 is limited to the northernmost sampling site. In addition, morphometric analyses revealed a unique head shape that characterized each genetic clade. Hence, both genetic and morphological evidence strongly suggests a hidden diversity within this common and commercially-important sardine.     

Reproductive biology and growth of bluestripe herring Herklotsichthys quadrimaculatus (Rüppell, 1837) in the northernmost waters

In order to examine the reproductive biology and growth of Herklotsichthys quadrimaculatus in the northernmost part of its reproductive range, the size frequency, gonadal development, and otolith daily increments of this species were collected from the coastal waters of Okinawa Island, southern Japan. Juveniles (<25 mm standard length, SL) were found from April to August. Their size increased to ca. 100 mm SL in November and subsequently remained unchanged. The gonadosomatic index of females was higher (>3.0) between March and August, which was the estimated spawning period. The modal hatching period back‐calculated from otolith daily increments was from April to May, which would be the peak of spawning. Because mature and spent ovaries also contained mature and immature oocytes, it was concluded that females spawn several times during the spawning season. Age determination from otolith increments showed logistic growth up to 97 mm (ca. 180 days post‐hatch), after which growth was almost stagnant. Maximum size and age were 121.6 mm SL and 384 days, respectively. The adult size decreased between August and September, indicating a change in the age cohort. Thus, the fish reached the end of their lifespans after spawning. Some of these ecological features were different from those of a previous study performed in southern areas; these differences suggest a flexible life history that could change to adapt to the surrounding environment.     

Variability of key biological parameters of round sardinella Sardinella aurita and the effects of environmental changes

We examined growth rates and reproductive characteristics of Sardinella aurita off Senegal and other coastal areas over a 20 year period (1995–2014) to determine how they relate to variations in environmental characteristics of coastal waters. Based on fish length-frequency data and a coastal upwelling index, we found that S. aurita recruitment tends to occur during the periods of most intensive upwelling (March–April off Senegal). Peak reproduction corresponds to periods of low sea-surface temperature (in February or March). The sex ratio was remarkably consistent during the 30 year study period and so was not affected by environmental changes. We hypothesise that S. aurita takes advantage of the higher zooplankton productivity that occurs in coastal waters when upwelling brings nutrient-rich water to the surface (i.e., it increases its growth rate and accumulates energy reserves for spawning). Growth performance appears to be strongly dependent on environmental conditions. The timing of spawning seems to occur when food (zooplankton) is most available for supplying the energy requirements needed by adults for spawning and early development of larvae. Environmental changes seem to have a significant effect on S. aurita growth and reproduction, which endorses their high phenotypic plasticity.     

Annual gametogenic cycle of the freshwater pearl mussel,Lamellidens marginalis (Lamarck, 1819) collected from a perennial lentic habitat of Bangladesh

ABSTRACT

We investigated the annual gametogenic phenology of the freshwater pearl mussel, Lamellidens marginalis (Lamarck, 1819), collected from a lentic habitat at Mymensingh, Bangladesh, using biometry and histology through monthly sampling from August 2015 to July 2016. After biometric measurements, thin slices of dorso-ventral sections were cut from the middle of the mussels for histology to determine sex and level of gonadal maturation. The condition index (CI) ranged from 0.64 (March) to 0.99 (January) over the study period. The CI peaked three times (January, April and July) indicating that the mussels were ripe during these months and subsequent decreases in CI indicated spawning, which was consistent with histology. Both males and females exhibited similar patterns in terms of gonadal development, maturation and spawning activity. It was confirmed that natural populations of L. marginalis spawn throughout the year with remarkable temporal variations, except during December when the surface water temperature reaches annual minima (16.5°C). Highest spawning activity of L. marginalis was noted during February–March, May and July–November. The data obtained in the present study could be useful for the conservation managers of this commercial species by allowing harvesting of better quality mussels to be timed without interrupting major spawning activity.     

Reproductive guilds (maturation,spawning frequency and fecundity) in the black pomfret,Parastromateus niger (Carangidae) in the Kuwaiti waters of the Arabian Gulf

Oogenesis, oocyte maturation pattern, spawning rhythm, spawning frequency, batch fecundity and oocyte diameter–frequency distribution of the black pomfret, Parastromateus niger (Bloch, 1795) in Kuwaiti waters were investigated from October 2003 to September 2005, using histological and morphological methods. The process of development is divided into four major phases: (i) primary growth phase; (ii) secondary growth phase; (iii) maturation phase; and (iv) spawning phase, followed by the regressed phase. Development of the yolky oocyte is an asynchronous process resulting, by the time of oocyte maturation, in a clear differentiation between a ready batch of oocytes (ready for spawning) and a reserve pool. Consequently, P. niger is capable of spawning multiple times throughout the reproductive season. Spawning frequency estimates, based on final oocyte maturation (FOM) method indicated that the species spawns once every 2.8 days during an 8‐month spawning season lasting from February to September, with a potential annual number of 22.4 spawns. Batch fecundity (BF) (2132–2001 648, mean 406 010 eggs), was significantly positively related to both standard length (SL) (P < 0.05) and ovary‐free body weight (OFBW) (P < 0.05), both parameters being good predictors of BF (r² = 30.8% for SL, from 22 cm onwards, and r² = 29.6% for OFBW, from 129.5 g onwards). No significant differences in monthly BF were found throughout the spawning season. Relative batch fecundity was 336 eggs/g OFBW; thus, estimate for potential annual relative batch fecundity was 7526 eggs g^?1 OFBW. The oocyte diameter–frequency distribution analysis revealed a multimodal distribution (at 100–200, 300–400 and 500–700 μm), confirming the evidence of multiple spawning.     

Life-history traits of Amur sleeper, <Emphasis Type="Italic">Perccottus glenii</Emphasis>, in the invaded Vistula River: early investment in reproduction but reduced growth rate

In recent decades, Amur sleeper is one of the most invasive fish species in Eastern and Central Europe. Generally, it is assumed that success of an invasive species can largely depend on the plasticity of its life-history traits, e.g., indicated by higher investment in reproduction in the initial stage of its invasion. On the other hand, such energy allocation to production of gonads should negatively impact somatic growth rate. The aim of this article was to explore this phenomenon in a non-native population of Amur sleeper inhabiting artificial reservoir on a large lowland river in Central Europe. Through analysis of the population age structure, sex-dependent growth rate and life-history traits we assessed investment in reproduction and its possible relationship with growth pattern as well as compared the results with literature data from native and introduced range. Samples collected monthly from April 2005 to March 2006 were used to estimate sex ratio, GSI, fecundity, eggs diameter frequency over the year, duration of spawning season, and mode of spawning. Age structure was calculated from scales and the same data were also used to back-calculate standard length (SL) at age. The population in the Włocławski Reservoir was represented by eight age groups, and its life span was one of the longest recorded both in its natural range and introduced areas. The weight–length relationship showed that the Amur sleeper grew isometrically and there was no difference between females and males. Although the Amur sleeper growth rate was relatively slow in the Włocławski Reservoir, its increment in the first year of life was comparable to that in other introduced areas and higher than in its natural range. The female age of maturation (1+) found in the reservoir was earlier than observed in its natural range as well as in most introduced areas (2+, 3+). Female length at maturation was similar to that reported elsewhere. The back-calculated standard length (SL) of females and males showed that in the first two age classes (1 and 2) males achieved larger SL than females. Meanwhile, at age 3, 4 and 5, females were larger than males but these differences were insignificant, except for class 5. For both sexes the average annual increment of SL decreased with age but in females the increment was always higher than in males (P < 0.05). The growth rate differences between females and males resulted possibly from their unequal investment in reproduction. Multiple spawning in the Włocławski Reservoir lasted from April to the end of August and was almost 3 months longer than in other regions. Thus, this higher investment in reproduction displayed by, e.g., earlier maturation of females and longer spawning season in the Włocławski Reservoir, may contribute to invasive success of Amur sleeper in newly colonized areas; however, the costs of this strategy result in slower growth in older age classes.     

Annual reproductive cycle and growth of the pen shell Atrina maura (Pterioidea: Pinnidae) on sand-bottom culture in the Ensenada Pabellones lagoon system,Gulf of California,Mexico

Abstract

The reproductive cycle and growth of the pen shell, Atrina maura, which was cultured in the Ensenada Pabellones lagoon system, Gulf of California, from March 2008 to March 2009, is described in this article. Histological techniques and the condition index were used to determine its reproductive condition. The sex ratio was 0.57 females:1.72 males within the population studied. There were no differences (χ², p < 0.05) in shell length (SL) between males and females. The mean length of the sampled specimens ranged between 50.99 ± 4.86 mm and 218.16 ± 8.87 mm. The histological results confirmed that A. maura is a gonochoristic organism that presents synchronic development of the gonads. The maturity and spawning phases were observed throughout the study period, with the exception of March and May 2008. The frequency of the gonad development stages obtained per month suggests that this species reproduced two times annually, with one important reproductive period from June to September, a minor reproductive period from November to February, and two resting periods as follows: July to August and January to February 2009.     

Length‐weight relationships of three fish species from the costal of Hainan,the South China Sea

Length‐weight relationships were determined for three fish species [Bregmaceros rarisquamosus Munro, 1950; Sardinella albella (Valenciennes, 1847) and Cynoglossus macrolepidotus (Bleeker, 1851)] inhabiting the coastal of Hainan, China. Fishes were collected using gillnets (mesh size 0.5 cm) and electrofishing from 2005 to December 2012. The b‐values of the equations ranged between 2.57 for Bregmaceros rarisquamosus and 3.34 for Cynoglossus macrolepidotus and thus were just inside the acceptable range for this value. Further, for B. rarisquamosus a new TLmax was recorded.     

Length–weight relationships of three fish species from the Bay of Bengal,Bangladesh

The present study describes the length–weight (LWR) of three fish species, Chela cachius (Hamilton, 1822), Coilia ramcarati (Hamilton, 1822) and Sardinella gibbosa (Bleeker, 1849) captured in the Bay of Bengal, Bangladesh, from December 2014 to November 2015. Fishes were captured with either gill nets (mesh size 2.0–5.0 cm) or set bag nets (mesh size 2.0–4.0 cm). The b values in the study varied from 2.88 (C. ramcarati) to 3.00 (S. gibbosa), with a mean a value of 2.94 at p < .001 for all three species. In addition, the study provides initial information on LWRs for C. cachius and C. ramcarati and maximum length records for C. cachius and S. gibbosa.     

Batch fecundity and spawning frequency of invasive Hemiculter leucisculus (Basilewsky, 1855) in Erhai Lake,China

Hemiculter leucisculus are multiple spawners with indeterminate fecundity, although previous fecundity estimates have assumed a determinate spawning pattern. Batch fecundity and spawning frequency of H. leucisculus were studied in Erhai Lake, China, in which the fish, as an exotic species, has become a successful colonizer. Spawning frequency was 16.05 %, as determined from the percent of females with postovulatory follicles 12 to 36 h old during the peak reproductive period (from May 27 to August 8). The average interval between spawning was 6.2 days and there were more than 16 total spawning batches during the peak reproductive period. The average batch fecundity (mean ± SD) was 11,934?±?5,921 hydrated oocytes in 40 females (standard length or SL: 9.1–14.4 cm), while relative batch fecundity was 560?±?137 eggs g^?1 wet weight. The total potential annual fecundity was approximately 190,944 oocytes over the whole spawning season and was much higher than the estimated standing stock (31,585 oocytes) of yolked oocytes (36 females, SL: 9.5–16.2 cm) at the beginning of the spawning season in April 2010. This high annual fecundity is likely to have contributed to successful invasion of Erhai Lake by H. leucisculus.     

Reproductive biology of the greyfin croaker <Emphasis Type="Italic">Pennahia anea</Emphasis> in the northern South China Sea

The greyfin croaker Pennahia anea is one of the most common croakers currently on retail sale in Hong Kong, but there are no regional studies on its biology or fishery. The reproductive biology of the species, based on 464 individuals obtained from local wet markets, was studied over 16 months (January 2008–April 2009) using gonadosomatic index (GSI) and gonad histology. Sizes used in this study ranged from 8.0 to 19.0 cm in standard length (SL). Both the larger and smaller size classes were missing from samples, implying that they are infrequently caught in the fishery. Based on GSI data, the approximate minimum sizes for male and female maturation were 12 cm SL. The size at 50% maturity for females was 14.3 cm SL, while all males in the samples were mature. Both GSI and gonad histology suggest that spawning activity occurred from March–April to June, with a peak in May. Since large croakers are declining in the local and regional fisheries, small species such as P. anea are becoming important, although they are mostly taken as bycatch. In view of unmanaged fishing pressure, and given the decline in large croakers and sizes of P. anea presently caught, proper management of the species is suggested.     

Gonad morphology and reproductive cycle of the mangrove oyster Crassostrea brasiliana (Lamarck, 1819) in the baía de Guaratuba,Paraná, Brazil

This study aimed to describe the gonadal histology and the reproductive cycle of Crassostrea brasiliana in the mangroves of Guaratuba Bay in southern Brazil. Adults were collected monthly from January 2010 to April 2011 from three sampling sites in intertidal oyster beds. The animals were evaluated using biometric and histological analyses of the gonads. The gonadal tissue samples were processed according to the standard histological procedures, and permanent slides were prepared using Harris' haematoxylin and eosin. The oysters were identified at the species level using a molecular protocol. Females (69%) predominated over males (26%), with 4% indeterminate and 1% hermaphroditic. Mature females were more prevalent in February, March and December 2010 and in March 2011. Mature males were more prevalent in February and April 2010 and in March 2011. The presence of hermaphroditic individuals was sporadic, and oysters in immature stages or sexual repose were observed in only a few collections between the months of May and October 2010. The reproduction of C. brasiliana in Guaratuba Bay occurs intermittently, but with greater intensity during the summer, with a larger number of females produced.