Mean Total Fecundity Research Articles

Biological characteristics of Orius similis Zheng (Heteroptera, Anthocoridae) by feeding on different aphid species as prey

The predatory flower bug Orius similis Zheng (Heteroptera, Anthocoridae) which originated in China is a polyphagous predator that feeds on a wide range of arthropod pests such as aphids, thrips and spider mites. However, sufficient information about the biological parameters of O. similis with different aphid species as prey is still lacking in the literature. Therefore, in the present work, development, mortality, longevity and reproduction of O. similis were studied in the laboratory with Aphis fabae (Scopoli), Aphis gossypii (Glover), Acyrthosiphon pisum (Harris), Myzus persicae (Sulzer) and Aphis pomi (De Geer) as prey. Prey species, their (prey’s) host plants and the age of the females had influenced the duration of embryonic development of O. similis. Nymphal developmental duration varied significantly according to prey species and (prey’s) host plant. The mean total nymphal developmental duration of both sexes was significantly shorter when feeding on A pomi [14.0 (♀♀) and 14.4 (♂♂) days] than with other aphid species as prey. Total mortality during the development was also affected by prey and plant species. O. similis was able to develop with different aphid species as prey and reach the adult stage. The different aphid species as prey and the sex of the predator had significantly influenced longevity, which was the longest in unmated females with A gossypii as prey. Pre-oviposition and oviposition period varied also significantly depending on prey species. Adult females started oviposition 4–6 days after emergence, and the mean total fecundity was significantly the highest with A pisum as prey with a mean of 161.3 eggs/♀. The ability of this predator to oviposit and develop with different aphid species as prey is discussed in relation to its practical use for biological control of aphids in protected cultivation.

Reproductive Characteristics and Egg Development in Flounder (Pleuronectes flesus luscus) in the Southern Black Sea

Spawning time, total fecundity, egg size, fertilization and hatching rates, and egg development of the flounder, Pleuronectes flesus luscus, were investigated in six wild female broodstock (mean wt 394.4±226.8 g). Spawning lasted 33 days from December 29 to January 30. Mean total fecundity was 171.4±109 x 103 eggs per female. Newly ovulated eggs were spherical and buoyant, with a diameter of 1.075-1.213 mm (avg 1.156±0.025 mm), a colorless transparent chorion, a slightly yellowish unsegmented yolk, and a narrow perivitelline space, without an oil globule. Fertilization and hatching rates were 17.2±15.7% and 51.5±27.6%, respectively. Hatching occurred after 117 h of incubation at 9.8-11oC. There were variations in egg size between batches, with the size tending to decrease during the spawning season (p<0.05).

Thermal Effect on the Biology and Life Tables of Bemisia tabaci Gennadius (Homoptera: Aleyrodidae)

The life history and life table of Bemisia tabaci Gennadius on cucumber was studied under laboratory conditions at 20, 25 and 30 degrees C. The overall developmental time varied from 34.8 days at 20 degrees C to 14.1 days at 30 degrees C. Immature mortality decreased from 45.8 to 17.3% with increasing temperature. The threshold temperatures of egg, 1st, 2nd, 3rd and 4th nymphal stage and a generation were 14.72, 14.36, 10.18, 11.40, 14.36 and 13.07 degrees C whereas the degree-day requirement at each stage was 64.44, 42.39, 49.19, 33.19, 35.46 and 229.52 DD, respectively. Female longevity ranged from 16.8-34.1 days. Mean total fecundity ranged from 150-263 eggs/female. Mean daily fecundity ranged from 4.2-12.7 eggs/female, increasing with increasing temperature. Values for r(m) varied from 0.066 to 0.191 being least at 20 degrees C and greatest at 30 degrees C. Generation times decreased from 43 to 19 days with increasing temperature. The results indicate that B. tabaci is well adapted to high temperatures and may extend its distribution if mean world temperatures increase as a result of global warming.

Suitability of the flour moth Ephestia kuehniella (Lepidoptera: Pyralidae) for three predatory phytoseiid mites (Acari: Phytoseiidae) in Egypt

The biology of Neoseiulus barkeri (Hughes), Typhlodromus balanites El-Badry and Amblyseius zaheri Yousef & El-Borolossy was studied using Ephestia kuehniella Zeller eggs as food source. For N. barkeri, the development was faster and reproduction was higher than for A. zaheri. Survival of immatures of T. balanites was low on eggs of E. kuehniella and all failed to develop to adulthood. A total of 50.4 and 41.0 eggs per female were obtained when N. barkeri and A. zaheri were fed on moth eggs, respectively. A diet of E. kuehniella eggs provided the highest female longevity and mean total fecundity which resulted in the highest net reproductive rate (R0 = 32.88), intrinsic rate of natural increase (rm = 0.139) and finite rate of increase (λ = 1.149) for N. barkeri. The mean generation time ranged between 24.65 and 25.03 days for A. zaheri and N. barkeri, respectively. The sex ratio of the progeny was strongly female biased (female/total = 0.69 and 0.58) when eggs of E. kuehniella were provided for N. barkeri and A. zaheri.

INVESTIGATIONS ON CERTAIN BIOLOGICAL AND ECOLOGICAL PARAMETERS OF THE CEREAL LEAF MINER Syringopais temperatella LED. (LEPIDOPTERA: SCYTHRIDIDAE)

The cereal leaf miner, Syringopais temperatella Led. (Lepidoptera: Scythrididae) has been a threatening pest on wheat over the last five years in Karak District-Jordan. The insect feeds on the plant foliage, soon turning its leaves into yellow and eventually leads to a sharp decline in production. Therefore, in order to establish control measures for this damaging pest, the current study was undertaken to investigate its biology (on wheat at 20±2°C), parasitoid, preference for certain plant species and the degree of distribution in the Karak District. Results showed that S. temperatella was able to develop on wheat and reach to adult stage. Mean total developmental period was 43.61 days. Total mortality was 74.70%. Sex ratio (females: males) of S. temperatella was 1: 0.39. Total parasitism by Anilastus sp. Forster (Hymenoptera: Ichneumonidae) reached up to 49.45%. Mean longevity of 11.36, 12.09 and 13.73 days for mated females, unmated females and males was recorded, respectively. The mean longevity of Anilastus sp. females with 15.64 days was significantly longer than that for males with 10.36 days. Maximum mean numbers of daily laid eggs by mated and unmated ones were 4.50 and 1.00 eggs/female, respectively. Mean total fecundity of mated females was 25.71 eggs/female, being significantly higher than unmated ones with only 4.73 eggs/female. Results also showed that S. temperatella preference among the different plant species tested was significantly greater for wild barely with a mean leaf area consumed of 2.04 cm 2 as compared to barely with a mean of 0.72 cm 2 or wheat with a mean of 0.37 cm 2 . Infestation by the cereal leaf miner is distributed at the central line extending from the northern to southern areas of Karak District.

A wild strain of Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae) from farm-stored maize in South Carolina: Effect of temperature on mating, survival, and fecundity

The purpose of this study was to develop age-specific survivorship and fecundity schedules for adult Plodia interpunctella (Hübner) relevant to maize storages, with special reference to the southeastern states (USA). Laboratory cultures were established with moths collected from farm-stored maize in South Carolina and maintained on cracked maize at 30 °C and 60% r.h. Age-specific schedules of survivorship and fecundity, the length of the oviposition period, mating success, and mating frequency were determined at 20, 25, 30, and 35 °C and about 75% r.h. The maximum oviposition period was longest (18 d) at 20 and 25 °C, and shortest (8 d) at 35 °C. The optimum temperatures for reproduction (mating frequency and fecundity) were 25–30 °C, but mean life-span was longest (13.2 d) at 20 °C and declined linearly with increasing temperature. Mean total (lifetime) fecundity ranged from 16.9 eggs at 35 °C to 227.7 eggs at 25 °C.

Age composition, growth, and reproduction of koi carp (Cyprinus carpio) in the lower Waikato region, New Zealand

A total of 566 koi carp (Cyprinus carpio) from the lower Waikato region were aged from scales and opercular bones, and growth was modelled with the von Bertalanffy growth function. There was no difference in growth rate between male and female carp. Growth of koi carp between zero and 3 years of age was lower than that of common carp in Europe and Australia. However, after 5 years of age the growth of koi carp was higher than that of common carp in Europe, but still below that of carp in Australia. Males rarely lived in excess of 8 years, whereas females lived to 12 years. Mean total fecundity calculated from 44 running‐ripe females was 299000 oocytes (±195600 SD) (range 29800–771000). Relative fecundity ranged from 19300 to 216000 oocytes kg‐1 total body weight, with a mean of 97 200 (±35 000 SD) oocytes kg‐1. Feral koi carp in the Waikato are capable of multiple spawnings within their lifetimes. Within a spawning season, Waikato populations of feral koi carp contained females that spawned once, and females that had the potential to have spawned repeatedly. Female gonadosomatic index (GSI) varied with season and was negatively related to water temperature.

Fecundity and Maturity of Orange Roughy (Hoplostethus atlanticus Collett 1889) on the Porcupine Bank, Northeast Atlantic

The first, comprehensive analysis of the fecundity and reproductive maturity of orange roughy, Hoplostethus atlanticus, from a specific area in the Northeast Atlantic is reported. Specimens were collected from aboard vessels, targeting this species on the Porcupine Bank (ICES subarea VII), in waters of between 1400 m and 1,650 m depth. Between September and December 2002, a non-random, stratified, sampling protocol was implemented by on board fisheries biologists to collect mature female fish between 300 mm and 540 mm SL. Ovaries from 65 individuals, representing the majority of 10 mm SL size classes, formed the analytical sample. A novel, digital method of oocyte counting was developed, allowing digital images of oocytes to be annotated, counted and stored. Total fecundity ranged between 20,352 and 244,578 oocytes per female and mean total fecundity was estimated to be 97,368 oocytes per female (SD = 48,322). Relative fecundity was estimated to be 33,376 oocytes per kg (SD = 11,407). Fecundity was shown not to decrease with age. Macroscopic analyses showed that 50% of females were not mature until they reached 27.5 years and 37 cm SL. Comparison with stocks from the southern hemisphere indicate that orange roughy from the Northeast Atlantic mature at a larger size and generally have a higher mean fecundity than those found in the southern hemisphere. This may reflect differences in growth rates influenced by environmental variables and fishing pressure.

Life Fertility Tables ofPiophila caseiL. (Diptera: Piophilidae) Reared at Five Different Temperatures

Abstract Piophila casei L. or cheese skipper is a well-known fly with a controversial role: it is considered harmful in the food industries but important in nature as a detritivore and useful for studies in forensic entomology. The temperature response of P. casei was studied at five constant temperatures: 15, 19, 25, 28, and 32°C. The lowest mortality percentage of eggs was recorded at 15°C and the highest at 32°C. Conversely, less mortality was observed for maggots at higher temperatures. The developmental time from first instar to adult decreased with temperature reaching the lowest value at 32°C (13.7 d). Adult longevity was strongly affected by temperature, decreasing from 20.5 d at 15°C to 6.6 d at 32°C. Mean total fecundity per female was higher at 25°C and lower at 15 and 19°C, whereas the best performance in mean daily total fecundity per female was recorded at 32°C. Male longevity followed a similar trend to the one observed for females. The net reproductive rate (R0) was greatest at 25°C, where...

Development, feeding and reproduction responses of Adalia fasciatopunctata revelierei(Mulsant) (Coleoptera: Coccinellidae) to Hyalopterus pruni(Geoffroy) (Homoptera: Aphididae)

This study was carried out to determine the development, survival and reproduction responses of Adalia fasciatopunctata revelierei (Mulsant) (Coleoptera: Coccinellidae) feeding on Hyalopterus pruni (Geoffroy) (Homoptera: Aphididae), using 20, 40, 80, 160 and 250 prey densities. All experiments were conducted at 25±1°C, 60±5% relative humidity, 16:8 light:dark under laboratory conditions. The average daily prey consumption of A. fasciatopunctata revelierei immatures and adults increased with increasing prey densities. Predation was not different for the larval stages at 80, 160 and 250 prey densities. The longevities of adult females were 35.67, 35.33, 49.00, 58.33 and 57.16 days when 20, 40, 80, 160 and 250 H. pruni were provided, respectively. The mean daily and total fecundity of A. fasciatopunctata revelierei increased with increasing prey densities. Females of A. fasciatopunctata revelierei feeding on H. pruni laid 89 eggs at 20 prey density and 301.67 eggs at 160 prey density. The search rate of females was higher than that of all larval instars; and the search rate of the fourth-instar larvae was higher than that of younger instars. Handling time decreased with development from larval stages to adult.

Phenology, fecundity and life table parameters of the predator Hippodamia variegata reared on Dysaphis crataegi

Phenological and some biological characteristics of Hippodamia (Adonia) variegata (Goeze) (Coleoptera: Coccinellidae), such as voltinism, hibernation, number of progeny produced by each generation, mating activity and sex ratio were studied, in order to evaluate the significance of this predator. The study of phenology was conducted in outdoor cages in Kifissia (Athens), during 1999--2001 and as prey was given Dysaphis crataegi (Kaltenbach). Hippodamia variegata completed seven generations between April and November. The hibernating population of H. variegata consisted of adults of 6th and 7th generations. The fecundity of the predator was studied under constant conditions [25 °C, 65% R.H. and 16:8(L:D)h photoperiod] in the laboratory and some population parameters were calculated: The total fecundity ranged between 789 and 1256 eggs, while the mean total fecundity was 959.6 eggs. The greatest proportion of eggs (45%) was oviposited in clutches of 11--20 eggs. The net reproductive value (R0) was found to be 425.9 females/female, the intrinsic rate of increase (rm) 0.178 females/female/day and the mean generation time (T) 34.0 days.

Suitability of the Pollen Grains, Ricinus communis and Helianthus annuus as Food for Six Species of Phytoseiid Mites (Acari: Phytoseiidae)

Laboratory studies were conducted on the acceptability of pollen grains of Ricinus communis (L.) and Helianthus annuus L. to Amblyseius zaheri Yousef and El-Borolossy, Euseius yousefi Zaher and El-Borolossy, Amblyseius lindquisti Schuster and Pritchard, Typhlodromus balanites El-Badry, Typhlodromus sennarensis El-Badry and Amblyseius cabonus (Schicha) as indicated by effect on development, survival, oviposition and life table parameters. A. zaheri and E. yousefi had a shorter developmental period on both pollen grains than A. lindquisti. Development was not completed in case of T. balanites, T. sennarensis and A. cabonus. A. zaheri and E. yousefi showed the highest oviposition rate when fed R. communis compared to H. annuus. A. lindquisti failed to lay any eggs when fed on both pollen grains. On both predator species, a diet of R. communis provided the shortest generation time (T) relatively, greatest female longevity and mean total fecundity (f) which resulted in the highest net reproductive rate (Ro) value (41.46 and 43.28 expected females per female), intrinsic rate of increase (rm = 0.279 and 0.258) and finite rate of increase (er m = 1.322 and 1.294 per day) for A. zaheri and E. yousefi respectively.

Maternal and seasonal differences in egg sizes and spawning activity of northwest Atlantic haddock (Melanogrammus aeglefinus) in relation to body size and condition

Egg and larval production of 22 captive spawning pairs of northwest Atlantic haddock (Melanogrammus aeglefinus) were monitored. Females spawned an average of nine egg batches (range 3–16) with a mean batch fecundity of 60 000 eggs and mean total fecundity of 535 000 eggs. Mean spawning duration was 37 days with a mean batch interval of 5.4 days. In multiple linear regression, male Fulton's condition factor (range 1.10–1.55) and mean batch interval explained 56% of variation in fertilization rate (33% and 23%, respectively). Seasonal composite egg diameter spanned 1.37–1.53 mm among females. Mean egg diameter within females declined seasonally by an average of 10.4% (37% by volume). Females produced 46 larvae per gram body weight. Body weight was the single best predictor of fecundity (r2 = 0.57), with Fulton's condition factor (range 1.04–1.76) explaining no significant additional variation over length or weight. Length and condition explained 39% of variation in seasonal composite egg diameter (22% and 17%, respectively) and body weight independently explained 32%. Sex-specific parental condition and body size acted through large egg size and elevated fertility to enhance reproductive output. Male spawning success was more sensitive than egg production to changes in condition.

Influence of host plant species of Bemisia tabaci (Genn.) (Hom., Aleyrodidae) on some of the biological and ecological characteristics of the entomophagous Serangium parcesetosum Sicard (Col., Coccinellidae)

The entomophagous Serangium parcesetosum Sicard (Col., Coccinellidae) is an effective predator of some whitefly species. However, information on the influence of the prey’s host plant species on its biological and ecological characteristics is still lacking in the literature. Therefore, the current study focuses on the possible influence of three greenhouse and two field host plant species of Bemisia tabaci (Genn.) (Hom., Aleyrodidae) on the number of eggs laid by S. parcesetosum. In addition, because of the economic importance and widespread planting of cucumber in greenhouses and cotton in the field, these plants were selected for further investigation into the development, mortality, longevity and reproduction of S. parcesetosum at a high temperature in the laboratory. Results showed that S. parcesetosum was able to lay eggs on all five host plant species of B. tabaci, whether greenhouse or field plants. However, among the three greenhouse plant species studied, S. parcesetosum females laid the highest number of eggs on cucumber followed by tomato and then sweet pepper. Of the two field plant species, significantly higher numbers of eggs were laid on tobacco than on cotton. S. parcesetosum could develop either on cucumber or on cotton as preferable host plant species for B. tabaci. There were significant differences in mean developmental duration of larval instars of the same sex between both host plant species; the duration was significantly shorter on cucumber than on cotton. There were no significant differences for mean total developmental duration from egg to adult emergence between both host plant species within the same sex; females showed a mean of 15.9 days and males of 15.1 days on cucumber, while on cotton the means were 17.2 days for females and 16.2 days for males. Total mortality percentage of S. parcesetosum during development from egg to adult stage was lower on cucumber than on cotton, 20.6 and 23.8%, respectively. Longevity of S. parcesetosum varied according to host plant species and sex with a mean of 63.4 days for females and 50.3 days for males on cucumber, and 92.4 days for females and 52.5 days for males on cotton. On cucumber, mean period of oviposition of S. parcesetosum was significantly longer than on cotton. Mean total fecundity was significantly higher on cucumber than on cotton, with means of 97.7 and 31.0 eggs/female, respectively.

Influence of temperature on the development, reproduction and longevity of Ceratothripoides claratris (Thysanoptera: Thripidae) on tomatoes.

Ceratothripoides claratris (Shumsher) is a serious pest attacking tomatoes in Thailand. Temperature-dependent development of C. claratris was studied at seven constant temperatures, i.e. 22, 25, 27, 30, 34, 35 and 40 degrees C. Pre-adult survivorship was greatest (95%) at 25 and 30 degrees C and shortest at 22 degrees C. Egg-to-adult time decreased within the range of 20 to 30 degrees C and at 34 degrees C it started to increase. The lower thermal threshold for egg-to-adult development was estimated at 16 and 18 degrees C by linear regression and the modified Logan model, respectively. The optimum temperature for egg-to-adult development was estimated at 32-33 degrees C by the modified Logan model. The influence of temperature on reproduction and longevity of C. claratris was determined at 25, 30 and 35 and 40 degrees C. Both inseminated and virgin females failed to reproduce at 40 degrees C. Virgin females produced only male offspring, confirming arrhenotoky. The sex ratio of the offspring of fertilized females was strongly female-biased, except at 25 degrees C. Mean total fecundity per female and mean daily total fecundity per female were highest for both virgin and inseminated females at 30 degrees C. Female longevity was longest at 25 degrees C and shortest at 40 degrees C. Male longevity was longest at 30 degrees C and shortest at 40 degrees C. The net reproductive rate (R0) and intrinsic rate of natural increase (rm) was greatest at 30 degrees C while, mean generation time (G) and the doubling time (t) were highest at 25 degrees C. The finite rate of increase (lambda) was fairly constant (1.1-1.5 days) over the three temperatures tested. The pest potential of C. claratris for tropical Asia is discussed.

Seasonal population dynamics of Typhlodromus pyri Scheuten (Acari, Phytoseiidae) in apple orchards in the region Meckenheim

Typhlodromus pyri Scheuten (Acari, Phytoseiidae) has been reported as the most important predator of the European red mite, Panonychus ulmi (Koch) (Acari, Tetranychidae) in apple culture. However, biological data on T. pyri was insufficient on important parameters like seasonal population dynamics and within-tree and on-leaf distribution in apple orchards in the region of Meckenheim, Germany. The purpose of the present work was, therefore, to obtain experimental data on these parameters of T. pyri from 2000 to 2002 in the apple orchards in this region. The results showed that overwintered females of T. pyri reactivate and start laying eggs between late March and early April. The mean daily number of the different stages of T. pyri per leaf peaked in July each year, where it ranged between 0.92–1.68 eggs, 0.81–1.41 nymphs, 0.64–1.32 females and 0.37–0.52 males. A significantly higher number of T. pyri individuals congregated in the bottom layer of trees (0.34–0.64 individuals/leaf) than in the middle and top layers (0.23–0.38 and 0.12–0.23 individuals/leaf, respectively). We found that 91.4–94.1% of the total eggs, 89.6–91.7% larvae, 73.0–76.5% nymphs, 60.5–64.6% adult females and 52.6–55.9% adult males concentrated their activities in the inner area of the leaf surface. More than 50% of the predatory mites congregated in the bottom layer in winter. Mean total density of the overwintering females in December of 2000,2001 and 2002 ranged between 10.6–14.2 females/5 cm twig in the bottom, 7.3–10.4 in the middle and 4.1–6.9 in the top layers of the apple trees. Mean total fecundity recorded over the 3 years was lowest in the overwintering generation with 31.8–37.6 eggs/female, highest in the June generation with 45.9–53.7 eggs/female, and intermediate in the August generation with 41.5–46.1 eggs/female. The overwintering generation was composed entirely of females, while the female to male ratio in the June generation was 2:1, and in the August generation 3:1. T. pyri overwinters as adult females in rough structures, cracks and crevices of twigs.

Comparative Life Table Statistics of Exochomus flaviventris Reared on the Cassava Mealybug, Phenacoccus manihoti, Fed on Four Host Plants

The demographic statistics of the ladybird Exochomus flaviventris Mader (Coleoptera: Coccinellidae) were investigated under laboratory conditions on the cassava mealybug, Phenacoccus manihoti Matile-Ferrero (Homoptera: Pseudococcidae), reared on four host plants with different levels of antibiotic resistance to the mealybug: two cassava (Manihot esculenta Crantz, Euphorbiaceae) varieties, Incoza and Zanaga, Faux-Caoutchouc (FC) (hybrid of M. esculenta × M. glaziovii Muel. Arg.) and water weed (Talinum triangulare Jack, Portulacacae). Preimaginal mortality, mean oviposition time and total fecundity of female ladybirds were strongly affected by the host plant even though there was no linkage with antibiotic resistance. The net reproduction rates RQ of the predator were 1.5, 1.7 and 2.4 times higher on Zanaga than on water weed, Incoza and FC respectively, and the generation time (T) was significantly longer on Zanaga than on the other three plants. The intrinsic rate of increase rm was not modified by the antibiotic resistance of the host plants. With the two cassava varieties, Incoza and Zanaga, it was found that antibiosis significantly affected the life history parameters of the ladybird without modifying its fitness, and provided better cassava mealybug control.

Parameters of reproductive activity in females of Harmonia axyridis (Coleoptera: Coccinellidae)

The effects of temperatures of 15, 20, 25 and 30°C on the duration of premating and preoviposition periods of Harmonia axyridis reared on the aphid Aphis fabae, were compared in the laboratory. The course of oviposition was monitored at 25°C in females reared on Aphis fabae and the peak of egg laying was recorded at the age of 15 to 45 days. The size of egg groups (batch size), as well as daily and total fecundity was recorded. Half of the total number of eggs was laid in batches of 10-30 eggs. The mean daily and total fecundity reached a maximum of 42 and 1,641.6 eggs, respectively. Adult females oviposited for almost their entire life.

Effects of Diet on the Biology and Life Tables of the Predacious Mite Agistemus exsertus (Acari: Stigmaeidae)

The biology of Agistemus exsertus Gonzalez was studied using two different insect eggs, Ephestia kuehniella Zeller and Parlatoria zizyphus (Lucas) as the food source. The development was faster and reproduction was higher when A. exsertus fed on eggs of E. kuehniella. A total of 97.78 and 75.27 eggs per female were obtained when eggs of E. kuehniella and P. zizyphus were provided respectively. A diet of E. kuehniella (eggs) provided the greatest female longevity and mean total fecundity which resulted in the higher net reproductive rate (Ro) value (61.25), intrinsic rate of natural increase (rm = 0.196) and finite rate of increase (rm = 1.22) per day for A. exsertus. A diet of P. zizyphus (eggs) resulted in close values of T = 21.70; rm = 0.174; e r m = 1.19. The sex rate of the progeny was strongly female biased (female/total = 0.72 and 0.66) when both eggs of E. kuehniella and P. zizyphus were provided.

Spawning pattern, length at maturity, and fecundity of the southern blue whiting (Micromesistius australis) in the south‐west Atlantic Ocean

Southern blue whiting (Micromesistius australis Norman, 1937) inhabits the waters of the Southern Hemisphere, and in the south‐west Atlantic Ocean is distributed over an area next to the Malvinas Islands. At present, this species is suffering over‐exploitation and its biomass has decreased drastically. The histological analysis of ovaries and the oocyte size frequency distribution of gravid females indicate that southern blue whiting is a batch spawner with determinate annual fecundity. The spawning season of M. australis in the south‐west Atlantic Ocean extends from August to October, with a main peak during September. Spawning females were recorded mainly in the waters south and south‐west of the Malvinas Islands, close to the 200 m isobath. Total fecundity of seven M. australis females ranged from 148 300 to 713 900 yolked oocytes (46–55 cm total length (TL)). The mean total fecundity was 477 700 (206 783 SD) oocytes for one 51 cm TL female. Mean relative fecundity was 706 (258 SD) oocytes per g female weight, ranging from 277 to 967. The percentage of sexually mature females for each total length class indicated 50% female maturity was reached at 37.8 cm. This value was similar to those reported for this species between 1980 and 1990.