Reproductive biology of the brown smoothhound shark Mustelus henlei,in the northern Gulf of California,México

Female brown smoothhound sharks Mustelus henlei were found to reproduce annually. A mature female carried both developing oocytes in the ovary and developing embryos in the uteri concurrently for c. 1 year. A great variability in the size of embryos was recorded each month, and the maximum embryo sizes were found from late January to mid‐March. The largest oocytes in mature females were observed in mid‐March. Gestation lasted c. 10 months. A linear relationship between maternal total length (L_T) and the number of pups per litter (litter size one to 21) was estimated. Birth L_T was reached in c. 280 mm. Females and males matured at 570–660 and 550–560 mm L_T, respectively. Difference in the litter size among Californian coast (one to 10) and northern Gulf of California (one to 21) populations existed for this smoothhound shark.     

Reproductive cycle of the blacknose shark Carcharhinus acronotus in the Gulf of Mexico

The reproductive periodicity of blacknose sharks Carcharhinus acronotus in the northern Gulf of Mexico was determined by examining reproductive tissues from specimens collected monthly from 2002 to 2005. Monthly changes in shell gland mass, right ovary mass and ovarian follicle diameter were assessed for 74 mature females. Temporal changes in testes mass, testes width and proportion of mature spermatocysts were examined for 64 mature males. Trends in female reproductive tissues suggested an annual peak in reproductive activity during June and July, while trends in male variables suggested an annual reproductive peak during May and June. Although male and female reproductive activity peaked in different months, a strong synchronicity existed between the proportion of mature spermatocysts and the diameter of the largest ovarian follicle. Based on these results, the mating season of blacknose sharks lasts from mid-May to July in the Gulf of Mexico. Maximum embryo sizes were observed in May, which suggested that partition occurs during late May or early June. Results indicate that blacknose sharks have a clearly defined annual cycle in the Gulf of Mexico. This conclusion is further supported by the complete absence of gravid females without vitellogenic ovarian follicles among all mature females examined.     

Reproductive biology of Carcharhinus acronotus in the coastal waters of South Carolina

The reproductive biology of blacknose sharks Carcharhinus acronotus in the western North Atlantic Ocean was studied by examining specimens collected in the coastal waters of South Carolina. Males begin the maturation process between 875 and 910 mm fork length ( L _F), as indicated by the presence of functional claspers and siphon sacs. The presence of vitellogenic oocytes and developing oviducal glands and uteri indicated that females begin to mature at c . 870 mm L _F. Length at which 50% of the population reached maturity was 896 and 964 mm L _F, equivalent to 4·3 and 4·5 years, for males and females, respectively. Gonado‐somatic indices suggested that spermatogenesis and vitellogenesis began after December. Mating took place during the end of May and the beginning of June. Fertilization occurred during late June and early July, suggesting that female blacknose sharks were capable of sperm storage. Based on the timing of fertilization and occurrence of females carrying near‐term pups in late May and early June, the gestation period for blacknose sharks was c . 11 months. Female blacknose sharks reproduced biennially based on the absence of vitellogenic oocytes in near‐term females and there being no indication of vitellogenesis in postpartum females. Male blacknose sharks were capable of reproducing annually as indicated by turgid genital ducts, which were observed in all mature males collected during late May and early June.     

Re-evaluation of reproductive cycle and fecundity of finetooth sharks Carcharhinus isodon (Valenciennes 1839) from the Northwest Atlantic Ocean,with new observations on ovarian cycle and reproductive endocrinology of biennially reproducing sharks

To provide updated information on life history for improved fishery management, the reproductive cycle of the finetooth shark Carcharhinus isodon from Northwest Atlantic (NWA) populations was investigated by examining temporal changes in morphology and histology of reproductive organs. Changes in plasma concentrations of gonadal sex hormones in relation to reproductive stage were also examined. Increases in testis width, epididymis head width, plasma testosterone concentrations and occurrence of mature spermatozoa were observed in male sharks between December and April, suggesting a seasonal pattern in reproduction that culminates with copulatory activity in May. Increases in maximum follicular diameter, oviducal gland width, plasma 17β-estradiol concentrations and occurrence of vitellogenic follicles were observed in non-pregnant female sharks during the same time period along with the occurrence of newly pregnant females in May, demonstrating strong synchronicity between male and female reproductive cycles. Pregnant females bearing full-term embryos were also observed in May, indicating that parturition occurs between mid-May and early June and gestation requires 12 months. Only transient temporal changes in follicle size and oviducal gland width were observed in pregnant females, indicating that reproductive periodicity is biennial; nonetheless, a single female exhibiting signs of concurrent vitellogenesis and pregnancy was observed. Mean brood size ± S.D. was 3.9 ± 0.9 offspring/female. Fecundity was not significantly correlated with female size, in part due to an unexpectedly high rate of early embryo mortality, which occurred in 11% of pregnant females, and was more common in larger individuals. Changes in ovarian activity during mid-pregnancy were observed, suggesting possible roles for the ovary in regulating some aspects of early to mid-gestation. This study confirms that earlier characterizations of the reproductive cycle and fecundity in NWA finetooth sharks remain valid for use in fishery management. This study also highlights unusual features of finetooth shark pregnancy (e.g., early embryo death, mid-pregnancy changes in ovarian function) that may have broader relevance to understanding elasmobranch reproduction.     

Reproduction and feeding habits of Mustelus dorsalis (Pisces: Triakidae) in the Gulf of Nicoya, Costa Rica: elements for a sustainable management

A total of 311 sharptooth smooth-hound Mustelus dorsalis were collected in the Gulf of Nicoya, Costa Rica from March 1999 to May 2000 to determine reproduction and feeding habits. The fishes were collected using hook and line. 250 females and 61 males were identified. The females are bigger (550-660 mm) and heavier (400-1,000 g) than males (500-585 mm and 200-300 g, respectively). All samples collected were mature and the minimum length to first maturity observed is 500 and 541 mm for females and males, respectively. From September to March individuals were mature, while samples caught during April and August were immature. A total of 1,259 embryos were analyzed. Number of embryos per liter ranged from two to six, the total length is from 130 to 205 mm and the weight from 6 to 35 g. This shark is a polyphagous opportunistic carnivore that preys on crustaceans (Squilla hancocki, S. parva, Litopenaeus sp.), fishes (Anchoa sp., Caranx sp., Lutjanus sp., Engraulis sp.) and mollusks (Loligo sp. and Octopus sp.). Main prey item was S. hancocki. The presence of mature sharks of both sexes along the year and the consumption of food items associated to shallow coastal rocky waters suggest that this sector of Nicoya Gulf is a nursery ground and an essential habitat. Based on these results the establishment of an integral management plan is proposed.     

Reproductive Strategies in Lemur catta: Balance Among Sending,Receiving, and Countermarking Scent Signals

Our goal is to go deep into behavioral olfactory strategies possibly used by ring-tailed lemurs in reproductive competition and to shed some light on the function of female scent marks deposited outside the breeding season. We followed 16 captive adults at the Pistoia Zoo (Tuscany, Italy) for > 1,500 h from May 1997 to March 1999. Male direct and indirect olfactory investigation on females showed complementary distributions, the former peaking during the breeding and the latter during the birth season. Males are thus able to monitor female reproductive conditions throughout the whole year. During the birth season there was an increase of female genital marking. The olfactory advertisement probably guarantees that the extremely brief estrus does not remain unnoticed and allows male intrasexual competition a long period to operate. Male indirect olfactory monitoring and countermarking on female signals peaked during the birth season, which suggests that male intrasexual competition is achieved both by getting female chemical messages and by concealing them from other males. Female countermarking on other female genital marks peaked during the breeding season. High-ranking females had higher frequencies of countermarking than those of low-ranking females, which suggests that the advantage of obliterating scent signals of other females is greater than the disadvantage of revealing one's own reproductive condition.     

The reproductive biology, age and growth of the North American cyprinid, Notropis longirostris (Hay)

Notropis longirostris (Hay), the longnose shiner, in Catahoula Creek, Jourdan River drainage, Hancock County, Mississippi, was studied from May 1970 to May 1972. In 1971 reproduction occurred from late March into October, as indicated by gross examination of testes, breeding tubercles and breeding colour in males, and ovarian weights, measurements of ova, and gross examination of ovaries in females. Gross examination of ovaries in 1970 also indicated an extended reproductive season. Generally no significant differences from a 1 : 1 sex ratio or in the size of males and females in collections taken during the reproductive season were indicated. Males and females matured about the same size. Most females were sexually mature when 29–30 mm SL. The smallest female with mature ova was 28 mm; however, the majority of females did not have mature ova until 31–33 mm. The number of mature ova produced prior to spawning ranged from 15 to 129 for females 30.8–44 mm SL. There were significant differences in the number of mature ova with time, two peaks being indicated: the first in late March and April at the beginning of the reproductive period and the second in early July about the middle of the season. This conclusion is also supported by ovarian weight measurements and length frequency histograms. The mean diameters of mature ova ranged from 0.70–1.05 mm, averaging 0.90 mm, and were not significantly correlated with length. Most fish live about 1–1.5 years and do not live through two winters, indicating an annual turnover in the population. Maximum size was about 48 mm SL. Specific characteristics of the life history pattern of N. longirostris are discussed in relation to ecological conditions of the habitat.     

Reproductive biology of Tilapia zillii (Gervais) in Lake Naivasha,Kenya

Synopsis Tilapia zillii breeds all year round in the equatorial Lake Naivasha with slightly high breeding intensity during wet months (March, May and July–August). A sex ratio of 1 : 1.28 was found between males and females. The smallest mature male and female were 9.0 and 11.0 cm respectively. The fecundity ranged from 2990 to 12344 eggs, with a mean of 6606 eggs. Fecundity showed a curvilinear relationship with total length (log F = 1.7034 + 1.6370 log L) and a linear relationship with body weight (F = 2197 + 28.76 W)     

Plasma steroid concentrations of adult male Atlantic sharpnose sharks, <Emphasis Type="Italic">Rhizoprionodon terraenovae,</Emphasis> in the northern Gulf of Mexico,with notes on potential long term shifts in reproductive timing

In previous literature it was proposed that Atlantic sharpnose sharks, Rhizoprionodon terraenovae, from the western Atlantic Ocean (WAO) population exhibited differences in their reproductive timing when compared to the northern Gulf of Mexico (GOM) population. The objective of the current study was to examine the reproductive cycle of mature male sharpnose sharks from the northern GOM population. Plasma testosterone (T) and estradiol (E₂) were measured from 76 mature male sharpnose sharks sampled from 1999 to 2001, and the gonadosomatic index (GSI) was determined for 53 additional mature males sampled from 2007-2008. Plasma T, E₂, and GSI exhibited similar cycles with peak values occurring in late spring (April/May) and lowest values occurring during the summer. These results suggest that male sharpnose sharks in the northern GOM are reproductively active one to two months earlier than previously reported, which now brings them into synchrony with the WAO population. Interestingly, this shift in reproductive timing corresponds with a 3.0°C (13.4%) increase in spring sea surface temperature (SST) from the Mississippi Sound over a 29 year period, which could translate into GOM male sharpnose sharks becoming reproductively active earlier in the year thus explaining the late spring peak in GSI.     

Distribution and reproduction of the southern lantern shark from New Zealand

Distribution, population structure and reproduction are described for the southern lantern shark Etmopterus granulosus at the Chatham Rise, New Zealand. Depth of capture for E. granulosus ranged from 744 to 1420 m, with highest catch rates between 800–1200 m. More than twice as many females as males were captured, and the majority of sharks caught were mature, indicating that there may be segregation according to sex and size class. Only 10 of 492 female sharks captured contained ova in uteri, and none contained embryos. The absence of pregnant females suggests that they move to another area or depth prior to pupping. Size of sharks captured ranged from 20·0 to 78·8 cm total length. Females began to mature at 62 cm total length, and males at 52 cm. There was no evidence of a seasonal reproductive cycle. Ovulation appeared to occur when ova reached a diameter of 40–45 mm. The average number of ova in mature females was 12·7. This information is crucial for assessing the impact of fisheries on E. granulosus populations.     

Trends in sightings and population structure of white sharks, <Emphasis Type="Italic">Carcharodon carcharias,</Emphasis> at Seal Island,False Bay,South Africa,and the emigration of subadult female sharks approaching maturity

A long-term sightings and photographic identification (photo-ID) database documented the inter-annual and monthly trends in white shark (Carcharodon carcharias) sightings, sex ratios and life-history stages at Seal Island, False Bay, South Africa, over the period 2004–2012. A total of 1105 sightings were recorded during 171 scientific surveys incorporating 577 h of observation (annual mean 64.10 h, range 23.71–178.69 h). The mean annual sighting rate was 1.87 (range 0.90–3.19) sharks per hour and sighting rates declined over the nine-year study period. It is unknown whether the decline resulted from an actual population decline, or was due to changes in shark distribution or environmental conditions, but it highlights the need for ongoing monitoring at this site. The overall sex ratio was 1.0: 1.0: 2.3 for male: female: unsexed sharks, respectively. Of the 1105 sightings, 39% (n = 433) were photo-ID’d, representing 303 individual sharks (112: 111: 80, male: female: unsexed) and 130 resightings. Of the 303 photo-ID’d sharks, 71% were sighted in a single year only, indicative of transient behaviour. Of the 29% of sharks that were resighted in more than one year, 65% were resighted in the following year, indicating site fidelity to Seal Island, whereas 35% skipped one or more years between encounters, indicative of a temporary absence. The majority (60%) of the photo-ID’d sharks were immature, 32% were subadult and only 8% were mature. No young-of-the-year sharks and few adults were recorded, indicating that Seal Island is not an adult aggregation site, nor a pupping or nursery area, but rather is best described as a seasonal feeding ground. Large females were rarely resighted again after they approached length-at-maturity (≥450 cm TL), whereas some adult males were recorded consistently across years. The emigration of subadult female sharks approaching maturity from Seal Island, combined with the small number of mature sharks of both sexes reported from any South African location, indicate that adult aggregation sites, and thus areas of reproductive importance, still remain unknown.     

Histological and morphological aspects of reproduction in the sandbar shark Carcharhinus plumbeus in the U.S. south‐eastern Atlantic Ocean and Gulf of Mexico

The reproduction of the sandbar shark Carcharhinus plumbeus in the U.S. south‐eastern Atlantic Ocean including the Gulf of Mexico was examined using a combination of histological and morphological characteristics of C. plumbeus collected through fishery‐dependent and ‐independent sampling programmes (n = 1,567). Indices of maturity were constructed using measurements of gonads, reproductive tracts and claspers, and sandbar sharks exhibited 50% maturity sizes of 140 and 148 cm fork length for males and females respectively. Gonado‐somatic indices and variation in reproductive tract condition were used to determine seasonal trends in reproduction of mature C. plumbeus. Sandbar sharks have discrete seasonal reproductive cycles in which males produce sperm from January to May with a peak in May and females develop eggs from January to May with ovulation occurring in June. Females were shown to exhibit a >2 year reproductive cycle. Embryonic development was assessed through measurements of masses and lengths of uterine contents. Gestation was 12 months, from July to the following June, with parturition in late June. This research highlights a difference from previously reported data on the periodicity of female reproduction in C. plumbeus in the U.S. south‐eastern Atlantic Ocean and Gulf of Mexico, which may have major effects on future C. plumbeus stock management.     

舟山及其邻近岛屿獐种群的初步研究

舟山海岛上的獐(Hydropotes inermis),定海县志(1923)已有简要记录。作者在1978年调查时发现,舟山岛及其邻近较大的岛屿上普遍有獐,1976年海岛獐单位面积产量,5倍于浙江大陆邻近10个县的产量(盛和林,1981)。为进一步合理利用和发展獐资源,继而对舟山岛獐的种群结构繁殖和种群增长等问题进行研究,同时又对邻近10多个岛屿进行了访问调查,兹将初步结果报道如下。     

Aggregation behavior of the grey reef shark, Carcharhinus amblyrhynchos, at Johnston Atoll, Central Pacific Ocean

Free-ranging female grey reef sharks, Carcharhinus amblyrhynchos, were observed forming daily aggregations offshore Sand Island, Johnston Atoll between March and late May from 1992 to 1995. Daily water temperatures were recorded at the aggregation area from 1993 to 1995. The annual aggregation cycle did not coincide with maximum or minimum annual water temperatures. During the 1994 aggregation, temperatures were recorded at least every hour at 7 sites in the Atoll. The sharks aggregated most frequently and in highest numbers at the largest and shallowest site, which also contained the fewest underwater structures. The water temperature at this site was 1–2 °C warmer than at neighboring sites and at a reef channel between the lagoon and the open ocean. The pattern of movement of sharks to and from the aggregation area was correlated with daily fluctuations of water temperature (r=0.38; p < 0.001), tide (r=0.30; p < 0.001) and light level (r=0.21; p < 0.001) after adjustment for autocorrelated errors. The daily maximum number of aggregating sharks coincided with the daily maximum water temperature. However, the number of aggregating sharks did not necessarily increase during days of higher water temperature. During the 1994 aggregation period, four sharks were fed ultrasonic telemetry tags, and telemetry stations were deployed at three sites within the aggregation area. Individual sharks were tracked returning to the aggregation area for durations of one to five days. The end of detection of tagged sharks is thought to be due to the regurgitation of the indigestible tags, rather than the sharks permanent departure from the aggregating area. Sharks aggregated only during the day; none of the tagged sharks were recorded and no sharks were ever seen at the aggregation area during night time. This revised version was published online in July 2006 with corrections to the Cover Date.     

Reproductive biology and population dynamics of the shortfin mako, Isurus oxyrinchus Rafinesque, 1810, off the southwest Portuguese coast, eastern North Atlantic

A total of 262 shortfin mako sharks, Isurus oxyrinchus, was sampled from the swordfish longliners operating in the eastern North Atlantic. Most were juveniles, with only 3.4% mature. Based on cohort analysis, average growth was determined as 61.1 cm year⁻¹ for the first year and 40.6 cm year⁻¹ for the second year. There was a marked seasonality in growth, with average monthly rates of 5.0 cm month⁻¹ in summer and 2.1 cm month⁻¹ in winter. Cohort analysis also indicated summer as the probable parturition season, with sharks close to birth size caught in May 2003 and July 2004. Length at maturity for males was estimated at 180‐cm fork length using the Schnute model. No females between 210 and 290‐cm fork length were caught, although this appears to be the interval where maturation occurs. Gear selectivity was considered as the probable cause for the low number of mature females sampled.     

Characteristics and environmental determinants of natality, growth and maturity in a natural population of the desert scorpion, Paruroctonus mesaensis (Scorpionida: Vaejovidae)

The scorpion, Paruroctonus mesaensis (Vaejovidae) has seven instar stages and moults six times. There is no post-reproductive moult. The average growth ratio between successive instars is 1–38. The average rate of weight increase is 000249/day. This rate fluctuates seasonally: it is highest in spring and lowest in winter and summer. Growth rate is a function of ambient burrow temperature and prey abundance. Body size is determinate. The growth rate of the pectines is significantly greater in males as compared with females. Analysis indicates that the pectines are a secondary sexual trait in males.
Animals mature from 19 to 24 months of age. Matings were observed from May through October. Gestation lasts 10–14 months. First surface appearance of newborn (instar II) is synchronous throughout the population and occurred in early August for five consecutive years. Some females were observed to be gravid for at least three consecutive years. Gravid females carry an average of 48–8 embryos. However, on the average only 19–9 young/female survive to appear on the surface. Factors which may be responsible for this observed decrease include resorption of embryos; death at birth, eclosion or first moult; and maternal and sibling cannibalism. The influence of various environmental factors on reproduction were analyzed. The number of newborn appearing on the surface and the population biomass of newborn showed a high positive correlation with precipitation and vegetation cover.     

Environmental variables affecting the sexual segregation of great white sharks Carcharodon carcharias at the Neptune Islands South Australia

The seasonal temporal sexual segregation of white sharks Carcharodon carcharias , at the Neptune Islands, South Australia, is described in relation to environmental variables. A significant sexual segregation was found at this site with sex ratios strongly favouring males overall. Males were more prevalent than females in all months in a 3 year sampling period, aside from April and May. There was a significant difference between the sexes in terms of mean daily numbers over the months of the study. It was also observed that sexual segregation fluctuated for unknown reasons on a temporal scale. Predictive models for estimating male and female numbers based on a series of abiotic factors were generated. Sea surface temperature, tidal height, tidal range, moon phase, cloud cover, underwater visibility and swell height were related to daily sightings of male and female white sharks to determine the influence of these variables on sexual segregation. Visibility and sea surface temperature affected male numbers, however, visibility did not affect sexual segregation. Tidal height was significantly different between males and females. Sea surface temperature also appeared to be related to sexual segregation in this species. Females were present when temperatures ranged from 15·7 to 18·1° C whereas males were observed at temperatures ranging from 14·3 to 17·8° C, with a peak in sightings in September, when sea surface temperatures were at their lowest. Since parturition is thought to occur in spring or summer, it is suggested that females are absent at this time and only return during prime feeding periods or times at which temperatures are elevated in order to increase developmental growth rates of their young. The significantly lower temperatures in 2003 may explain the absence of females in this year. Hypotheses related to temperature regulation in this species are put forward to explain the sexual segregation observed.     

Gonad development and sperm motility of the diving beetle Cybister brevis Aubé, 1838 (Coleoptera: Dytiscidae) in response to seasonal changes in Japan

Gonad maturation in wild Cybister brevis Aubé, 1838 from Japan was investigated to determine the physiological mating season. Breeding experiments showed that hatching occurred from May to September, and the peak was observed in July. The gonadosomatic index (GSI) in collected females (ovary development) showed the highest value in May. The GSIs were low in other seasons. On the other hand, the GSIs in collected males (testes and accessory glands) remained at constant values during the experimental period. Interestingly, high sperm motility was exhibited in May and September, whereas it was low in December and March. This indicates the maturation difference between females and males. Females mature only at the beginning of the breeding season (May), but males do so from May to September. This result suggests that males have a wide-ranging maturation period and earlier sexual maturation than females, ensuring a successful fertilization.     

Reproductive biology of the greeneye spurdog Squalus chloroculus (Squaliformes,Squalidae)

The reproduction of the greeneye spurdog Squalus chloroculus was studied based on animals caught in the multispecies and multi‐gear southern and eastern scalefish and shark fishery on the upper continental slope off southern Australia. One hundred and ninety‐nine females (502–990 mm, total length, L_T) and 189 males (515–810 mm L_T) were examined. The female reproductive cycle, based on 41 breeding animals, is continuous and triennial, with the pregnancy period estimated to be 31–34 months, seasonal and synchronous with the ovarian cycle; a third of the breeding female population is estimated to give birth between September and December each year. The estimated L_T at which 50% of females are mature is 799 mm (95% c.i. : 794, 804), whereas the L_T at which 50% are maternal is 825 mm (95% c.i. : 817–833), but these estimates are probably biased by the phenomenon of apparent change of L_T at maternity and L_T at maturity following severe length‐selective fishing mortality. Litters ranged from four to 15 embryos with a 1:1 sex ratio, and litter size increased with maternal length. The breeding cycle of males is neither seasonal nor synchronous with the female cycle. The estimated L_T of males where 50% are mature was 629 mm (95% c.i. : 603, 645).     

Reproductive biology of the fanray, <Emphasis Type="Italic">Platyrhina sinensis</Emphasis> (Batoidea: Platyrhinidae) in Ariake Bay,Japan

The reproductive biology of the fanray, Platyrhina sinensis, was examined in Ariake Bay, Japan, from May 2002 until December 2006. Females reached sexual maturity at a larger size than males [total length (TL) at 50% sexual maturity: male, 393 mm; female, 421 mm]. The present data support a distinct annual reproductive cycle for P. sinensis. The gonadosomatic index (GSI) for mature males showed a clear seasonal trend, declining from August to November. Histological observations showed that mature sperm in the testes occurred from August to November when monthly GSI declined. Concomitantly, pre-ovulatory ova were observed in females collected from August to November. These data indicate that mating, ovulation and fertilization occurred from August to November. Near-term embryos, neonates and recent post-partum females also occurred from August to November. Additionally, all post-partum females possessed large pre-ovulatory ova. Parturition occurred from August to November followed immediately by mating, ovulation and fertilization. Mature females become pregnant every year, and the gestation period is almost 1 year. Fertilized uterine eggs without macroscopic embryonic development were present throughout the annual reproductive cycle, indicating that P. sinensis utilizes embryonic diapause as its reproductive strategy. Both reproductive tracts of females were functional, and fecundity ranged from 1 to 12 with a mean of 6.0, increasing with TL.