Indeterminate Fecundity Research Articles

Reproductive biology of thin sharpbelly, Toxabramis swinhonis Günther, 1873 in a shallow lake (Biandantang Lake) along the middle reach of the Yangtze River basin (China): implications for fisheries management

The reproductive biology of Toxabramis swinhonis, one of the most abundant bycatch species in freshwater fishery in China, was first reported based on 783 specimens collected in Biandantang Lake, central China from October 2016 to September 2017. The overall sex ratio (female/male) was 1.03:1, not significantly different from the expected value 1:1. Nevertheless, sex ratio varied with seasons: 1.32:1 in the early stage of the spawning season (March–April), while 0.46:1 in the later stage (July–August). The monthly succession of the average gonadosomatic index (GSI) and percentages of mature individuals co-indicated that T. swinhonis was a spring-summer (March–August) spawner. Further, the bimodal distribution of the size of eggs from one gravid ovary and histological analysis of mature gonads suggested that T. swinhonis was a multiple spawner with indeterminate fecundity and high degree of spawning asynchronicity. The sizes and ages at first maturity for females and males were 84.47 and 81.86 mm, and 1.62 and 1.56 yr, respectively. The batch fecundity (FB) of this species varied in a wide range from 2006 to 73592 eggs per fish with a mean value of 26487.15 ± 2675.61 (S.E.) eggs and increased with the increasing of the gonad weight (WG), eviscerated weight (WE), total length (LT) and age (A). Overall, T. swinhonis in Biandantang (BDT) Lake is characterized by high fecundity and prolonged spawning season, resulting in easy population explosion. Thus, to remove T. swinhonis moderately or release predator fish discreetly to control its population is proposed considering its reproductive characteristics.

Queen Triggerfish Reproductive Biology in U.S. Caribbean Waters

AbstractEffective fisheries management requires a detailed understanding of the life history strategies of managed species. The Queen Triggerfish Balistes vetula supports productive fisheries in the western Atlantic, including the U.S. Caribbean. We utilized a combination of fishery‐dependent and fishery‐independent samples to assess the size structure, sex ratio, size at maturity, spawning season, and spawning frequency for a Queen Triggerfish population in the U.S. Caribbean. From 2013 to 2018, 1,148 samples were collected, ranging in size from 67 to 434 mm FL. This study provides important life history information from an exploited population and is the first to describe Queen Triggerfish reproductive biology in detail for the Caribbean. We documented that the Queen Triggerfish is a sexually dimorphic species characterized by a medium size at maturity. The smallest sexually mature male and female were 184 and 215 mm FL, respectively. Lengths at 50% sexual maturity (L50) for males sampled from Puerto Rico and St. Croix, U.S. Virgin Islands, were similar (206 and 211 mm FL, respectively) and were significantly smaller than the L50 values for females (Puerto Rico: 256 mm FL; St. Croix: 245 mm FL). Queen Triggerfish, nesting benthic spawners, exhibited group‐synchronous oogenesis and indeterminate fecundity over the spawning season that started as early as the week after the full moon in December and extended until August. Spawning interval, defined as the number of days between spawning events in a female, was 54–55 d, indicating that a female could spawn up to five times over the estimated 241–267‐d spawning season. As regulations on grouper and snapper species in the Caribbean increase, Queen Triggerfish will experience increasing fishing pressure. Managers should continue to evaluate potential impacts of this pressure and establish management regulations that consider the region‐specific reproductive season and size at maturity.

Reproductive parameters of Atlantic chub mackerel Scomber colias in M'diq Bay, Morocco

AbstractReproductive biology of Atlantic chub mackerel (Scomber colias) was studied based on samples from commercial catches in M'diq Bay, Morocco. Females predominated in the total catch (54%), their size at first maturity being 19.19 ± 0.43 cm TL. A minimum landing size (MLS) of 21 cm is suggested. The oocyte size frequency distribution and histological analysis confirmed that S. colias is a species with an indeterminate fecundity. The batch fecundity was estimated as 18,452–131,642, with a mean of 60,022 oocytes. The relative batch fecundity was 157–360, with a mean of 279 eggs g−1.

Insight on reproductive strategy in Portuguese waters of a commercial protogynous species, the black seabream Spondyliosoma cantharus (Sparidae)

Information on fish reproductive strategy is essential to understand population dynamics. Samples of black seabream, Spondyliosoma cantharus, were collected from the western Portuguese continental coast to investigate the reproductive cycle, the timing of spawning, length at maturity and sex change, fecundity type and fecundity. This species is a protogynous hermaphrodite, showing a sharped biased sex ratio towards females for lengths smaller than 25 cm, and significantly biased towards males above this value, with no females occurring above 35 cm. Development of secondary growth follicles was asynchronous, and it was estimated that each female spawns 27 batches during the spawning season, which takes place from February to May. Half of the females’ population was mature at 18.41 cm and have changed sex at 25.62 cm. Sex change takes only a brief period of time, as transitional individuals were scarce and most showed oocytes regressing into cystic structures. The species presents a clear indeterminate fecundity type with massive atresia happening at the end of the spawning season. Mean values of 203 oocytes and 5431 oocytes by gram of eviscerated female were estimated for relative batch fecundity and relative annual fecundity, respectively.

Diplectrum radiale (Quoy & Gaimard, 1824) (Serranidae): A rare case of simultaneous hermaphroditism in a teleost fish

AbstractThis study generates, for the first time, information on the reproductive traits of the simultaneous hermaphrodite Diplectrum radiale. The specimens were captured bimonthly in two distinct ecosystems along the south‐eastern Brazilian coast. The mature ovotestes were removed, preserved in formalin and examined using histological techniques. The results revealed indeterminate fecundity with asynchronous ovarian organization. All spermatogenesis occurs within cysts, and the spermatogonial distribution indicated an unrestricted testicular type. The testicular and ovarian tissues were separated from each other by different ducts, indicating no possibility of internal self‐fertilization. The hydrated oocytes were stored in the accessory reproductive structure for at least 24 hr. The presence of atretic hydrated oocytes within this structure and the positive periodic acid–Schiff reaction of the villi‐like projections revealed the function of the ovary sinus as absorbing unspawned oocytes. The relative batch fecundity ranged from 62 to 209 oocytes/g (126 ± 42) for specimens from the coast and from 52 to 203 oocytes/g (113 ± 57) for those sampled in the estuary. The potential batch fecundity was linearly related to size, weight, and the gonadosomatic and hepatosomatic indices, revealing that these parameters significantly affect the reproductive potential of D. radiale.

Fecundity regulation strategy of the blue jack mackerel, Trachurus picturatus (Bowdich, 1825), off Madeira Island (NE Atlantic)

This contribution intends to verify the type of fecundity regulation of the blue jack mackerel. For this purpose, the oocyte development process was analysed. A total of 158 ovaries were sampled between January 2009 and April 2010 from purse-seiners operating in the Madeira Island waters, NE Atlantic Ocean. Histological analysis and visual image analysis system were used to study the four main criteria applied for fecundity type determination: (1) presence of a hiatus between pre-vitellogenic and vitellogenic oocytes; (2) number of standing stock of advanced vitellogenic oocytes over the spawning season; (3) mean size of standing stock of advanced vitellogenic oocytes over the spawning season; and (4) the incidence of atresia over the spawning season. The analysis of the oocytes size frequency distribution showed that no distinct hiatus could be observed between pre-vitellogenic and vitellogenic oocytes during the spawning season. Considering the whole spawning period but the last month that was poorly sampled, the number of standing stock of advanced vitellogenic oocytes showed no decrease trend along the spawning season, the mean diameter of cortical alveoli oocytes and of the advanced stock of vitellogenic oocytes did not increase over the spawning season and the relative intensity of atresia was always high throughout this period. These findings suggest the blue jack mackerel displays an indeterminate fecundity.

Closely Related Fishes Inhabiting Different Ecosystems Exhibit the Same Oocyte Production and Recruitment Pattern.

Information on oocyte production and recruitment in phylogenetically related species can help in understanding the evolution of reproductive life-history traits in fish of indeterminate fecundity. The present study compared, for the first time, oocyte production and recruitment patterns between two closely related species: Stellifer brasiliensis and Stellifer rastrifer (Perciformes, Sciaenidae), in the southwestern Atlantic, Brazil. Specimens of S. brasiliensis were sampled from the coastal waters of Ubatuba, and samples of S. rastrifer were taken from the Cananéia Lagoon Estuarine System. Ovaries were investigated using histology and model-based stereology. The total number of oocytes per individual (N) and stage-specific oocyte packing density did not differ significantly between S. brasiliensis and S. rastrifer The number of pre-vitellogenic and vitellogenic oocytes were positively correlated with female total weight and length, and ovary weight in both species. Analysis of oocyte recruitment across their development stages revealed that approximately 5.9% of the standing stock oocytes larger than 50 μm in S. brasiliensis and 5.0% in S. rastrifer were recruited to form the next batches. Females of S. brasiliensis and S. rastrifer, in spawning-capable phase, exhibit the same oocyte production and recruitment patterns, showing no influences of the ecosystems on primary and secondary oocyte production.

Oocyte development and fecundity type of the Brazilian Snapper Lutjanus alexandrei Moura & Lindeman, 2007 (Perciformes: Lutjanidae).

Lutjanid species exhibit multiple spawning behaviour during an extended spawning season in warm months, asynchronous oocyte development and indeterminate fecundity. Although early studies have contributed to knowledge of the reproductive cycle of many species within the group, they have not considered aspects about the number of cortical alveoli oocyte stage throughout maturity phases along spawning season. The latter aspect is also considered very important to confirm indeterminate fecundity hypothesis. In the present study, were analyzed 154 Brazilian snapper Lutjanus alexandrei female gonads obtained from artisanal fisheries in Pernambuco State (Brazil) between October 2010 and March 2011. Were measured oocyte size frequency distribution for maturity phases (developing, spawning capable and actively spawning), and oocyte development stage (unyolked oocytes, cortical alveoli, primary, secondary and tertiary vitellogenic oocytes and hydrated oocytes), and also the oocyte stage frequency during spawning season. The frequency of cortical alveoli oocyte stage was constantly found in the spawning period (>37%), showing slight variation throughout maturity phases. The absence of gap in the oocyte size frequency distribution between primary and secondary oocyte growth stages during spawning season is a strong indicator of continuous oocyte recruitment from reserve stocks. In addition, co-occurrence of tertiary vitellogenic oocytes, hydrated oocytes, post-ovulatory follicles and yellow-brown bodies in the histological sections of ovaries reinforce indeterminate fecundity hypothesis.

Stable isotope evidence for income resource allocation to egg production in the Japanese anchovy Engraulis japonicus

For multiple-batch-spawning fish species with indeterminate fecundity, income breeding might be more rewarding than capital breeding, because it can fine-tune their reproductive output in terms of maternal condition and offspring survival rate. Although income breeding has been suggested for many small and short-lived pelagic fishes, direct and quantitative evidence for resource allocation to egg production is lacking. This study determined the resource allocation strategy in the Japanese anchovy Engraulis japonicus under ad libitum food availability by using carbon and nitrogen stable isotope ratios (SIRs) as quantitative indicators. Initially, feed with low SIRs was provided and then switched to feed with high SIRs for monitoring the changes in the SIR of eggs during the spawning season. The effect of the latter feed on eggs was evident with the increasing SIRs for both carbon and nitrogen after the diet was switched, suggesting that income resources were primarily used over a season. However, the estimated transfer rates of the resources from food intake to eggs produced varied along with the degree of prevailing temperature. Our findings also suggested that, although well-fed female Japanese anchovy are largely income breeders, the resource allocation strategy used for egg production might be more complicated than previously thought.

A Reappraisal of Reproduction in Anadromous Alewives: Determinate versus Indeterminate Fecundity, Batch Size, and Batch Number

AbstractInnovative methods for analysis of reproduction may provide more information that can be used to conserve species of concern. We present data on oocyte development, batch size, and batch number of anadromous Alewives Alosa pseudoharengus in a lake‐spawning population located in Connecticut. We sampled female Alewives as they arrived at the spawning habitat (uprunners) and females as they were leaving (downrunners). We estimated batch size by weighing all oocytes and performed image analysis on oocytes in subsamples of some ovaries, thereby estimating oocyte size‐frequency distribution to define the number of batches. We performed both whole‐mount and histological analysis on other ovaries to compare gravimetric and stereological estimates of batch size and to precisely characterize oocyte developmental stages. Uprunners had advanced oocytes at the ultimate stage of vitellogenesis and usually three additional less‐developed batches. Postovulatory follicles and oocytes that were being resorbed were prevalent in downrunners but were absent in uprunners. Females spawned at least three batches in a season; however, downrunners had nearly as many batches as uprunners in their ovaries, indicating there was continuing recruitment and maturation of fresh batches. A numerical model of oocyte growth indicated that there is sufficient time for batches recruited at the beginning of the spawning season to develop and be spawned in the same season, indicating that fecundity is indeterminate. Accurate assessments of individual reproductive performance will require detailed consideration of within‐season oocyte dynamics as opposed to relying on enumerating oocytes in prespawners.Received November 25, 2014; accepted July 13, 2015

Reproductive traits of the pompano, Trachinotus ovatus (Linnaeus, 1758), in the north-western Mediterranean

This study describes for the first time the reproductive traits of the warm-water pompano, Trachinotus ovatus. Specimens were sampled from landings by artisanal fishing vessels in the NW Mediterranean. Monthly collections, from July 2010 through to September 2012, yielded 226 individuals (118 females and 108 males). The size at 50% maturity (L50) was estimated at 30.9 and 29.1 cm TL for females and males, respectively. Specific reproductive traits, such as oocyte size-frequency distributions, presence of recent post-ovulatory follicles along with oocytes in the final phases of gonadal development, and massive atresia in post-spawning individuals, indicated that pompanos are multiple batch spawners with asynchronous oocyte development and indeterminate fecundity. Monthly variations in the gonadosomatic index and in the phases of gonadal development indicated July and August as the spawning season. There were also noticeable inter-annual variations in spawning phenology, mean diameters of the oocytes, relative batch fecundity and eggs quality, all of which corresponded to changes in sea surface temperatures. This study enhances our understanding of the need for research into the reproduction of warm-water species, which are currently expanding into the increasingly warmer waters of the world's more northerly seas and oceans.

Reproductive biology of an endemic amphidromous goby, Cotylopus acutipinnis, from La Réunion Island

Amphidromous gobies living in the rivers of tropical islands display a high continuous reproductive effort in response to environmental unpredictability. Females are usually able to spawn a large number of eggs over an extended season, which contributes to offset the high larval mortality. The increasing human pressure on the insular aquatic systems threatens these gobies and highlights the urgent need to acquire knowledge on their biology for management purposes. The present study investigated the reproductive traits of the endemic amphidromous goby, Cotylopus acutipinnis, in a river of La Réunion Island. Ovarian histology showed that females were multiple spawners with a group-synchronous ovarian follicle development and an indeterminate fecundity. Females reproduced from 28.6-mm TL and laid their eggs in a unique event (from 3226 to 106840 eggs), with a spawning frequency of ~1 month or less. The drop in reproductive activity coincided with lower water temperatures and a decrease in daylight duration. Evidence suggested that spawning activity was not disturbed by flooding events recorded a few days before sampling. We suggested that the temperature threshold inducing the ovarian growth (18.3°C for C. acutipinnis) could be a determinant factor explaining the specific repartition of gobies throughout the river.

Reproductive dynamics of Pacific sanddab, Citharichthys sordidus, off the central coast of California

Female Pacific sanddab were collected from the Monterey Bay, California to describe their reproductive strategy and annual reproductive cycle, as well as to estimate length at maturity, fecundity, spawning fraction (SF), and spawning interval (SI). Captive females were held to examine degradation of spawning markers and confirmed the biological spawning capabilities of the species. The reproductive season extended from May through January, as determined through macroscopic and histological examination of ovaries. Oocyte development was asynchronous, and an indeterminate fecundity pattern was displayed. Absolute and relative batch fecundity values were variable (means=6663 eggs and 54eggsg−1 somatic weight, respectively) and significantly related to maternal length. During the period of highest reproductive activity, SF ranged from 0.42 to 0.98, suggesting some females were spawning on a daily basis. Monthly SF and SI were related to length, with smaller females having a truncated season and lower SF compared to larger females. Lengths at 50% (119mm) and 95% (149mm) maturity showed a downward shift relative to the 1940s, though the magnitude and cause of this shift remain unknown. This study highlights the importance of considering demographic shifts and size-related dynamics when modeling a stock's reproductive potential.

Estimating fecundity in the zygoparous species Helicolenus dactylopterus (Actinopterygii, Scorpaeniformes): adaptation of the gravimetric method

Bluemouth, Helicolenus dactylopterus is zygoparous species with internal fertilization spawning multiple batches of early-celled embryos in gelatinous masses. Its unusual reproductive strategy required methodological adjustments to estimate potential annual fecundity. The present study applied an adaptation of the gravimetric method, estimated batch fecundity based on different spawning fraction criteria (gestation, early-celled, and blastula females), and compared these estimates with the number of developing oocytes (NDOR) in the beginning of spawning to clarify the oocyte development pattern. Spawning fraction estimation based on the gestation criterion was considered the most reliable given its low variance and the subjectivity of staging early-celled embryos. On average, 87 batches were spawned with a mean spawning interval estimated at 1.73 days, and a mean relative annual total fecundity of 1,773 embryos g−1 carcass. The inexistence of a clear decreasing trend in the NDOR throughout the spawning season, and the lower NDOR estimates in females in the beginning of spawning comparing with relative annual fecundity (gestation criterion) suggests vitellogenic oocyte recruitment supporting previous results of indeterminate fecundity in Portuguese coast. The method proposed can be considered in fecundity studies of other commercial important species which extrudes gelatinous egg masses.

Health and reproduction of red mullet, Mullus barbatus, in the western Mediterranean Sea

The reproductive and general health of exploited fish stocks is an essential element of sustainable and profitable fisheries. The main purpose of this study was to assess the relationships between reproduction and two important parameters of fish health (parasitism and energy reserves) in female specimens of red mullet, Mullus barbatus, from the western Mediterranean Sea. We present new data for this species on (i) the prevalence and intensity of infection by metazoan parasites; (ii) the total lipid content in muscle and gonads as a measure of condition and (iii) fecundity and egg quality as a measure of their reproductive capacity. The results show that M. barbatus is a batch spawner with an income breeding strategy, an asynchronous development of oocytes and indeterminate fecundity. The results also indicate that the three most abundant and prevalent parasites significantly affect the condition and reproduction of M. barbatus. Specifically, the digenean, Opecoeloides furcatus, causes a reduction in the female’s energy reserves, while the nematodes, Hysterothylacium fabri and H. aduncum, produce a rise in egg production but impair egg quality. These implications of the relationships between parasitism, fish health and fish reproduction should be taken into consideration in the assessment and management of exploited species.

Oogenesis and Fecundity Type of Gray Triggerfish in the Gulf of Mexico

AbstractThe fecundity of Gray Triggerfish Balistes capriscus has been difficult to estimate, as few imminently spawning or recently spawned females have been detected. Our study focused on verifying the pattern of oogenesis and fecundity type in Gray Triggerfish. During 1999–2012, females (n = 1,092) were collected from the eastern Gulf of Mexico, and subsets of these fish were used to calculate condition indices and assess ovarian histology. The gonadosomatic index, hepatosomatic index, and Fulton's condition factor indicated that liver and somatic energy stores increased prior to spawning and were depleted throughout the spawning period, characteristic of a capital pattern of energy storage and allocation to reproduction. Typical of a capital breeding pattern, we also observed (1) a hiatus in oocyte size distribution and (2) group‐synchronous oogenesis, which are both traits of a determinate fecundity type. However, evidence that fecundity was not set prior to spawning included the observation of “de novo” vitellogenesis during the spawning season; secondary oocytes increased in number and failed to increase in mean size over time. Thus, Gray Triggerfish exhibit an indeterminate fecundity type with mixed reproductive traits that may characterize species exhibiting female parental care in warmwater environments. Further, we estimated the secondary oocyte growth rate (37 m/d) based upon the time lag of postovulatory follicle (POF) degeneration. Using oocyte growth rate and the proportion of females bearing POFs, the interspawning interval was estimated to range from 8 to 11 d, indicating that 8–11 batches/female could be produced during the estimated 86‐d reproductive period. The hiatus in oocyte size distribution was used to define a minimum size (250 m) from which to distinguish an advancing batch of secondary growth oocytes. Batch fecundity (BF) ranged from 0.34 to 1.99 million eggs and was significantly related to FL (mm): BF = 8,703.69·FL – 1,776,483 (r2 = 0.56).Received October 10, 2014; accepted June 27, 2015

Understanding the determinate–indeterminate fecundity dichotomy in fish populations using a temperature dependent oocyte growth model

The fecundity type (determinate vs. indeterminate) is still uncertain for many commercially important fish populations affecting accuracy in fecundity estimations and hindering the selection of appropriate egg production methods for stock assessment purposes. It is broadly considered that boreal fish populations living in colder habitats are determinate spawners whilst populations residing in warmer habitats tend to be indeterminate spawners. In the present study we modelled the determinate–indeterminate fecundity type in batch spawning fishes, i.e. fish that spawn several batches of eggs per spawning season, based on the relationship between oocyte growth period and the duration of the spawning period considering that both variables can be affected by water temperature and latitudinal distributions. Individual based models (IBMs) were developed to explore how the interaction of these variables can result in a series of patterns along the continuum from extreme determinacy, i.e. annual fecundity being recruited long before the onset of the spawning period, to indeterminacy. Model simulations showed that fish stocks with oocyte growth periods longer than the spawning period are predicted to exhibit determinate fecundity which provides a fair justification for why cold water species with slow oocyte growth and limited spawning periods are determinate spawners and vice versa.

Stereological comparison of oocyte recruitment and batch fecundity estimates from paraffin and resin sections using spawning albacore (Thunnus alalunga) ovaries as a case study

Traditional histological protocols in marine fish reproductive laboratories using paraffin as the embedding medium are now increasingly being replaced with protocols using resin instead. These procedures entail different degrees of tissue shrinkage complicating direct comparisons of measurement results across laboratories or articles. In this work we selected ovaries of spawning Mediterranean albacore (Thunnus alalunga) as the subject of our study to address the issue of structural changes, by contrasting values on oocyte recruitment and final batch fecundity given from the same tissue samples in both paraffin and resin. A modern stereological method, the oocyte packing density (OPD) theory, was used supported by initial studies on ovarian tissue sampling and measurement design. Examples of differences in the volume fraction of oocyte stages, free space and connective tissue were found between the embedding media. Mean oocyte diameters were smaller in paraffin than in resin with differences ranging between 0.5% in primary growth and 24.3% in hydration (HYD) stage oocytes. Fresh oocyte measurements showed that oocytes shrank as a consequence of the embedding process, reaching the maximal degree of shrinkage for oocytes in the HYD stage (45.8% in paraffin and 26.5% in resin). In order to assess the effect of oocyte shrinkage on the OPD result, and thereby on relative batch fecundity (Fr), oocyte diameters corrected and uncorrected for shrinkage, were used for estimations. Statistical significant differences were found (P<0.05) between these two approaches in both embedding media. The average Fr was numerically smaller in paraffin compared to resin (86±61 vs. 106±54 oocytes per gram of body mass (mean±SD)). For both embedding media statistical significant differences (P<0.05) were seen between Fr results based on either oocytes in the germinal vesicle migration stage or HYD stage. As a valuable adjunct, the present use of the OPD theory made it possible to document that the oocyte recruitment of spawning ovaries of Mediterranean albacore followed the typical pattern of an asynchronous oocyte development and indeterminate fecundity.

Determinate Versus Indeterminate Fecundity in American Shad, an Anadromous Clupeid

AbstractHistorical fecundity estimates of American Shad Alosa sapidissima used a determinate method that estimated annual fecundity as the standing stock of oocytes at a single point of time prior to spawning. Such fecundity estimates have been (1) reported for populations from the Canadian Maritimes to Florida, (2) applied to hypothesis tests of life history evolution, and (3) used in demographic models to advise management policy. However, American Shad have asynchronous development of yolked oocyte clutches, which suggests that new oocytes could arise after spawning commences, biasing the results of a determinate fecundity method downward. If so, annual fecundity should be a product of batch size and the number of batches—an indeterminate fecundity method. We investigated oocyte recruitment, atresia, and spawning intervals using gonad histology of females from the Mattaponi River, Virginia. Batch size (i.e., the number of hydrated oocytes prior to a spawning event) was estimated using a gravimetric method. Spawning duration was obtained from an independent acoustic tagging study. A size hiatus between primary and secondary oocytes was only evident in some individuals during spawning, so we conclude that an indeterminate fecundity method is necessary for this population of American Shad. Atresia was evident during spawning but was low at the end of the 2002 spawning season. Females spawned every 2.2–2.9 d, releasing 11–17 batches per season. Batch fecundity (range: 12,700–81,400) was 23% higher for repeat versus virgin spawners. A bootstrapped estimate of potential annual fecundity for a virgin female—as calculated with an indeterminate fecundity method—was 478,000–544,000 eggs (95% confidence interval), about double the previous (determinate) estimates from this river system (260,000 and 288,000). Until more comparisons are done with other populations, we urge caution in using the many published determinate fecundity estimates of American Shad and other Alosa species.

Reproductive ecology of the glacier lanternfish Benthosema glaciale

Myctophids play a key role in the transfer of energy in pelagic food webs, linking zooplankton to higher trophic levels. Data are presented, for the first time for the glacier lanternfish (Benthosema glaciale), on maturity ogives, size-at-maturity and reproductive strategy in terms of ovarian organization and fecundity type in two contrasting environments: North Atlantic and Mediterranean. We analysed 292 females collected in Flemish Cap during early summer 2009 and 2011 and off the Balearic Islands during late autumn 2009 and early summer 2010. The spawning season differed between areas. Size at 50% maturity in Flemish Cap was 47.6 and 49.1 mm in 2009 and 2011, respectively, but significantly smaller, 24.5 mm, in the Balearic sea. B. glaciale is a batch spawner with asynchronous ovarian development and indeterminate fecundity. Batch fecundity showed significant relationships with length and weight, although average relative batch fecundity was low (1031 ± 396 oocytes/gram). We compared two staining techniques: Hematoxylin–eosin and PAS–hematoxylin–metanil yellow with the latter being more useful to detect mature females and spawning indicators in regressing and regenerating females. Our results contribute to a better understanding of the reproductive potential and ecological role of this species, the most abundant myctophid in the northern Atlantic.