Growth and production of Euphausia lucens in the southern Benguela Current

The growth rate of a population of Euphausia lucens from thewest coast of South Africa was estimated from laboratory studiesand from monthly size-frequency distributions of samples collectedover a 1-year period. Laboratory studies indicated that growthrates ranged from 0.131 (larvae) to 0.047 mm day^–1 (juveniles),while size-frequency distributions suggested a growth rate of{small tilde}0.026 mm day^–1 for the adults. The mean annualbiomass from the inshore, intermediate and offshore regionsranged from 9.75 to 47.29 mg dry wt m^–3 with the highestbiomass being found in the inshore region. Calyptopis larvaewere present for most months of the year, indicating continuousrecrwtment. The relative contribution of flesh, moults and eggsto the total annual production was estimated separately forall three regions. Production due to growth (P_g) was estimatedto be 92.71–185.60 mg dry wt m^–3 year^–1, whileexuviai production (P_e) varied between 60.01 and 281.38 mg drywt m year Production of eggs (P_r) was estimated to range from5.07 to 12.39 mg dry wt m year the lowest value being obtainedin the inshore region. Moult production represented {small tilde}6times the mean biomass in each region, while the P/B ratio forflesh production varied from 3.92 to 8.91, the highest ratiobeing obtained in the offshore region. Total P/B ratios rangedfrom 10.14 to 16.01.     

Vertical migration and feeding of Euphausia lucens (Euphausiacea) in the Southern Benguela

Diel migration and feeding were examined for populations ofEuphausia lucens living in the near- and offshore waters ofthe southern Benguela. Euphausiids at both stations displayednocturnal diel vertical migration patterns. Animals inshoreascended in a slow-fast-slow manner which seems to be relatedto differential food concentrations throughout the water columnPronounced quantitative and qualitative changes in the dietof E.lucens were observed offshore but not inshore. These differencesare discussed in relation to different ambient food environments     

Population parameters and reproductive biology of the Iberian hareLepus granatensis in southern Iberia

To analyse the population structure and reproductive biology of the Iberian hareLepus granatensis Rosenhauer, 1856, 498 hares (264 males and 234 females) were collected in monthly samples from October 1998 to September 1999. Females reached larger sizes than males, with approximately 400 g difference in body mass on reaching sexual maturity. The total sex ratio was 1∶1, with a bias in favour of males in winter. Sexually active males and females appeared in every month but August, when no sexually active female was found. Births occurred in every month and were more frequent between March and July. Seasonal variation in kidney fat index (KFI) followed a similar pattern in males and females, with an increase in mid-autumn and a decline at the end of winter. Reproductive activity appeared in every month, with a maximum from February to June. Reproductively hyperactive females (simultaneously pregnant and nursing) appeared in every month except in January, with a first peak in March and a second lower peak in May–June. Litter size fluctuated between 1 and 7 leverets. The most frequent gestations involved 1 or 2 foetuses. The mean annual litter size was 2.08 and the average number of litters per productive female per year was estimated to be 3.48. The maximum productivity was recorded between March and May. The total annual production of young per adult female was estimated to be 7.21. The minimum annual survival rate of young was 27.91%. On the basis of these results we propose to maintain the limit of the hunting period between October and December. We discuss the relationship between the low young/adult ratio obtained and the hunting method used.     

黄海南部太平洋褶柔鱼种群结构与繁殖生物学

依据2008年11月—2009年9月黄海南部帆张网太平样褶柔鱼渔业调查资料,分析了太平样褶柔鱼胴长组成结构、性比、初次性成熟胴长以及胴长与体重关系等基础生物学参数的季节变化,阐述了该海域太平洋褶柔鱼种群结构动态及繁殖生物学特征。结果表明:太平洋褶柔鱼在该水域常年均有分布,其中秋、冬季以性成熟个体为主,春、夏季以幼体为主;该水域太平洋褶柔鱼雌性个体数量显著多于雄性,总性比为0.60,当胴长(LM)在190～280mm范围内时,性比(rsex)与胴长之间的关系符合:rsex=3×10-5LM1.8017;雌、雄个体的性腺成熟度均呈现随胴长增大而升高的趋势。该水域太平洋褶柔鱼个体的性腺体指数月变化显著,以秋、冬季较高,春、夏季较低,表明该水域太平洋褶柔鱼群体的繁殖季节主要集中在秋、冬季;性腺体指数与性腺成熟度(除Ⅴ期外)和胴长之间均存在正相关关系。雌性个体的初次性成熟胴长较大,为201.9mm;雄性较小,为174.3mm。不同性腺成熟度阶段,太平洋褶柔鱼胴长与体重的关系不同,在其个体生长发育后期,体重增加主要受性腺发育的影响。     

Population structure and reproductive biology of Atlantoscia floridana (van Name, 1940) (Crustacea, Isopoda, Oniscidea) in southern Brazil

Data were obtained on the population structure and reproduction of Atlantoscia floridana, one of the most common species of terrestrial isopods in the restinga (coastal dune) forests of the state of Rio Grande do Sul, southern Brazil. During a 19-month period, a total of 7833 individuals were sampled: 2792 males, 3400 females and 1691 mancas. There was a significant difference between the size of both males and females collected in 2000 and 2001: the mean size was smaller in the second year when individuals in the larger size classes were lacking. Population density varied with season. The minimum population was 131 ind per m² individuals, the maximum 1040 ind per m² and the mean 450  per m². While the overall sex ratio was clearly female biased, the operational sex ratio favored males, and showed no changes with season. Because both ovigerous and post-ovigerous females were present throughout the year, reproduction is considered continuous; however, reproduction peaked during autumn and spring. Ovigerous females were measured (CW = cephalothorax width) and the number of eggs was counted. Fecundity (F) varied from 5 to 23 eggs ( = 11.18 ± 4) per female, and was expressed by the regression F = –18.48 + 22.59 CW, with the female cephalothorax width varying from 1.04 to 1.68 mm. Marsupial mortality was only 0.9%. Egg production was 588 eggs per m² in spring and 660 eggs per m² in autumn. Recruitment occurred in all months, and eggs, embryos and marsupial mancas were also present year-round. A. floridana is the dominant species of terrestrial isopod in the study area. Its most remarkable characteristic is its high reproductive investment.     

Population age structure in males and juveniles of the Antarctic Krill,Euphausia superba Dana

Summary Further results are reported on the age structure of populations of the Antarctic krill, using the age pigment lipofuscin. Study of the males shows a five-year adult life span as in females in an earlier study. Only a single age group was found in the juvenile stage.     

Population structure and reproductive biology of Schilbe intermedius (Teleostei: Schilbeidae) in the Pendjari River,Benin

This study, the first on fish reproduction in the Pendjari River, investigated aspects of the reproductive biology of Schilbe intermedius. A total of 429 females and 239 males were collected from March 2007 to February 2008. Females were larger than males and the sex ratio was 1:1.8 in favour of females. Size at first maturity was estimated to be 14.9 cm and 16.1 cm for males and females, respectively. Absolute fecundity ranged from 1 006 to 83 980 (22 421 ± 16 083) oocytes, and mean relative fecundity was 201 ± 162 oocytes g^?1 of total body mass. Frequency distributions of oocyte diameter suggested synchronous development, with total spawning. Spawning lasted from June to November, coinciding with peaks in rainfall and flooding. Larger females began spawning about two months before smaller ones.     

Age,growth, and reproductive biology of the Atlantic spadefish Chaetodipterus faber in southern Brazil

Ichthyological Research - This is the first study to investigate the age, growth and reproductive biology of the Atlantic spadefish Chaetodipterus faber in southern Brazil. A total of 625...     

Notes on the reproductive biology of brachiopods from southern New Zealand

Abstract

The gonads of Notosaria nigricans, Terebratella inconspicua, T. ronguinea, Liothyrella neozelanica. and Neothyris ienticuiaris from southern New Zealand are described and their breeding state is determined. Attempts to induce spawning were not successful even with individuals that appdatred ripe. Sinlce normal fertilisation did not take place even with stripped gametes, it is concluded that either the brachiopods examined were not fully ripe or some indeterminate factor was inhibiting normal development of the zygotes.     

Population structure and reproductive biology of the fiddler crab Uca inversa (Hoffman, 1874) (Brachyura: Ocypodidae)

The population structure and reproductive biology of Uca inversa (Hoffman) were studied in Mozambique for the first time. Crabs were randomly sampled on monthly basis during low tide periods from January to December 2002 at Costa do Sol mangrove, Maputo Bay, southern Mozambique. A total of 1131 crabs was obtained, of which 518 (45.8%) were males, 322 non-ovigerous females (29.3%) and 281 (24.8%) ovigerous females, respectively. The present population presents non-normal size frequency distributions, with males reaching greater size than females. The overall sex ratio (M:F) (1:0.84) was significantly different from the 1:1 ratio. Ovigerous females were present throughout the year and the embryonic development showed synchrony with the gonadosomatic index, in which females carrying eggs close to hatching were more abundant when the gonadosomatic index reached minimum values in the population. Egg number increases with female size. Juvenile recruitment was also continuous with high proportion of young recruits being recorded in winter, probably due to the high reproductive activity displayed in summer. U. inversa exhibits a rapid embryonic cycle accompanied by a rapid larval development and settlement in the study area.     

Female reproductive biology of the sand smelt in brackish lagoons of southern France

The breeding season of Atherina boyeri living in the brackish lagoons of Mauguio, Pérols and Méjean (Hérault, southern France) was very protracted (February-September). The peak of the reproductive effort occurred in April, May and June. Larger fishes started spawning earlier, and stopped later, than smaller ones. Batch fecundity varied from 4 to 447 oocytes and was positively related to female length and weight. Monthly mean fecundity increased at the beginning of the breeding season and decreased between June and July. Individual mean oocyte diameter ranged from 1.34 to 1.94 mm and was not related to fish length. Monthly mean oocyte size declined throughout the breeding season as water temperature rose. There was no trade-off between number and egg size. The strategy of these sand smelts seemed well adapted to ensure spawning success without endangering their survival. The highest reproductive effort period occurred in such a way that environmental conditions were suitable to the best survival and growth of hatched larvae. When breeding ceased, fishes, particularly the youngest ones, had enough time to improve their condition before overwintering.     

Variation in the genetic structure and reproductive biology of holm oak populations

Five polymorphic enzymatic loci were studied in 30 populations of Quercus ilex distributed from Crete to North Africa. A high within-population genetic diversity was found for each locus studied. Most of the alleles were common to all the populations, indicating that the holm oak corresponds to a single genetic entity. Observation of breeding system characteristics showed that the holm oak is monoecious, wind-pollinated, and likely to possess genetic autoincompatibility. Furthermore, studies of flowering phenology in a single population showed that the period of flowering varied notably among trees. An average of 29% of the trees showed inter-annual variation in flowering time. The male, female or vegetative investment also varied widely among trees from one year to another. This results in a diversification of pollen source received by a given tree each year, and also from one year to another.     

The colony structure and reproductive biology of the afrotropical Mashona mole-rat, Cryptomys darlingi

Cryptomys darlingi occurs in the mesic Miombo woodland of north-eastem Zimbabwe. It occurs in colonies of up to nine individuals, in which reproduction is limited to one of the largest males and the largest female in the colony.
Reproduction and details of colony size and number of breeding animals in a colony are described for five complete field-captured colonies.
In captivity, mating is not confined to a particular season, and up to three litters of pups are orn per annum. The reproductive female initiates the pre-copulatory behaviour. The gestation lengti is 56–61 days ( n = 2 ). The new-born pups are altricial and litter size is small = 1.7 ± 0.5 ( n = 6). In this case, the pups first left the nest 10 days after birth, began to eat solids when 14 days old, and were fully weaned at five weeks. They began to spar with each other when 36–40 days old, but did not disperse and were incorporated into the colony. This suggests that the Mashona mole-rat colonies are composed of a founding pair and at least three successive litters of pups.     

Population structure and reproductive biology of Pygospio elegans (Polychaeta: Spionidae) on an intertidal sandflat, Firth of Forth, Scotland

Abstract. The population structure and reproductive biology of a population of the spionid polychaete Pygospio elegans was studied at Drum Sands, Firth of Forth, Scotland, between March 1997 and February 1998. P. elegans was numerically dominant at the site and exhibited a population density increase through the sampling period. The population showed a seasonal pattern with two acute periods of recruitment during the year, one in spring and one in winter. Planktotrophic larvae were the only larval type produced throughout the sampling period. Larvae were released at the 3–5 setiger stage and settled at a size of 18–22 setigers. The spring recruits grew at a rate of 23 setigers per month, reaching sexual maturation size during September of the same year. The adult sex ratio was female-biased throughout the study period (mean = 2.99:1 ± 0.51). When female:ripe male sex ratios were highest (summer and fall), the proportion of females brooding larvae decreased suggesting that sexual reproduction is seasonal. Asexual reproduction was not observed in the population of P. elegans on Drum Sands. These findings suggest that a high degree of variability is a trait of the reproductive biology of P. elegans. .     

Species-specific genetic markers for identification of early life-history stages of Cape hakes, Merluccius capensis and Merluccius paradoxus in the southern Benguela Current

The correct identification of fish egg and larval stages is crucial for inferring spawning areas and subsequent dispersal routes for marine fishes. The authors use species-specific mtDNA polymerase chain reaction to estimate proportions of Merluccius capensis and Merluccius paradoxus eggs and larvae and to elucidate early life stage distribution patterns in the southern Benguela system.     

Surface-feeding on cephalopods by procellariiform seabirds in the southern Benguela region, South Africa

Cephalopod beaks recovered from stomach samples taken from 14 seabird species in the southern Benguela region off Southern Africa and from one species at Sub-Antarctic Marion Island, were identified as far as possible, counted and the lower rostral lengths (LRLs) measured. Dorsal mantle lengths (DMLs) and body masses of the cephalopods eaten were estimated. The results of analyses by percentage frequency of occurrence and numerical abundance are discussed with reference to present knowledge of the distribution of cephalopods eaten by seabirds in the areas studied. Division of the cephalopod component of seabird diets into species which float, and species which sink, after death indicates that the birds forage on dead or moribund cephalopods on the surface, rather than catching live bioluminescent cephalopods at night.     

广西北仑河口红树植物种群结构与动态特征

以广西北仑河口国家级自然保护区4种红树植物秋茄(Kandelia obovata)、桐花树(Aegiceras corniculatum)、白骨壤(Avicennia marina)和木榄(Bruguiera gymnorrhiza)为研究对象,在野外样地调查的基础上,采用高度级和大小级结构、静态生命表、存活曲线、时间序列分析和7种聚集强度指数等方法对4种红树植物的种群结构和动态进行了分析和预测,旨在阐明红树植物种群与群落的结构特征和动态变化规律以及潜在的驱动机制,为广西红树林生态系统的保护与恢复提供基础资料和科学依据。研究结果表明:木榄和秋茄种群更新良好,桐花树更新受到一定阻力,种群相对稳定,白骨壤种群更新不良,呈现明显的衰退趋势;4种红树植物种群不同龄级的存活量差别较大,存活量和生命期望一般随龄级的增加逐渐减少;白骨壤种群的存活曲线属于DeeveyⅠ型,其种群个体均能达到其平均生理寿命,木榄和秋茄种群属DeeveyⅡ型,各龄级个体具有相对一致的死亡率,而桐花树种群介于DeeveyⅠ型和DeeveyⅡ型之间,其幼龄期死亡率偏高,中龄期后死亡率逐渐接近;时间序列分析同样表明,白骨壤未来种群数量将明显降低,种群逐步衰退,桐花树未来种群数量将表现为稳中有降,而木榄和秋茄未来种群数量将趋于增加。4种红树植物不同龄级种群多呈现聚集分布,聚集强度往往随种群龄级的增加而趋于降低。上述结果表明,北仑河口4种红树植物的种群动态与群落所处演替阶段息息相关,先锋植物白骨壤种群处于较快衰退阶段,演替前中期的桐花树种群稳中有降,而演替中后期的秋茄和木榄种群出现不同程度的增长,反映出本次调查的红树林群落正处于演替的中期阶段,白骨壤和白骨壤+桐花树群丛将逐步演替为以木榄为优势种的群丛。此外,红树植物的种群动态受到自身繁殖特性、生境条件、种内和种间竞争、虫害等多种因素的调控。     

Population structure and reproductive biology of a freshwater fish,Labeo boggut (Sykes, 1839), from two perennial rivers of Yamuna basin

Population structure and reproductive biology of an important and less studied freshwater carp, Labeo boggut (Sykes, 1839), from two perennial rivers of Central India were studied between January 2008 and December 2009. Maximum three annual rings were found and used to assess growth data in samples representing 0 to 3+ year classes. LWR indicated positive allometric growth in males and females of both rivers. Asymptotic length (L_∞) and growth co‐efficient (K) were 22.5 cm and 0.5 year^?1 for the Betwa River; and 23.6 cm and 0.6 year^?1 for the Ken River. Growth performance index (ø’) was higher in the Ken than in the Betwa. Reproduction was between June and September and GSI of both sexes were maximal in mid‐June, thereafter declining until September. Mean size at first sexual maturity was 12.2 cm (n = 12) for females and 13.2 cm (n = 8) for males in the Betwa, and 12.5 cm (n = 13) TL for females and 13.1 cm (n = 9) TL for males in the Ken. The exploitation level (E) and maximum allowable exploitation (E_max) limit of L. boggut was 0.23 and 0.36 in the Betwa, whereas it was 0.33 and 0.37 in the Ken. These presented biological traits and population characters of L. boggut from both rivers provide first basic information for use in future assessment and conservation planning.