Reproductive costs to male and female worm pipefish

Prior to reproductive maturity male and female worm pipefish Nerophis lumbriciformis are not significantly different in standard length ( L _S), eviscerated mass or condition indices. Subsequently, however, mature females achieve significantly ( P  < 0·001) greater values of L _S and mass. For egg-bearing males, there was no marked difference in the mass of embryos with increasing development ( P  > 0·1); similarly there was no significant divergence in condition indices calculated for males carrying embryos of increasing development. Post-brooding males, however, had significantly lower values for the hepato-somatic index than either egg-bearing or non-mated male worm pipefish ( P  < 0·001). This study suggests that male worm pipefish invest a significant proportion of their energy budget into the development and maintenance of the brooding patch, to the detriment of increased length or mass.     

Reproductive biology of two sympatric skates in the south‐west Atlantic: Psammobatis rudis and Psammobatis normani

The total lengths ( L _T) at which 50% were mature of Psammobatis rudis and Psammobatis normani , in the south‐west Atlantic were: P. rudis , 428 mm for males and 414 mm for females and P. normani , 443 mm for males and 403 mm for females. Clasper length in mature males was greater in P. normani than in P. rudis , whereas oviducal gland width was not different between species. Females of P. normani with egg cases were found in every month sampled, and in January, March, April and July in P. rudis , although insufficient samples were available to identify peak oviposition times. Geographic variation in size frequency and maturity were found. The effects of oceanographic conditions and fishing pressure are discussed. Size at 50% maturity in both species was >74% of the maximum L _T, indicating late sexual maturity and low potential stock recovery rate.     

Reproductive biology of the southern thorny skate Amblyraja doellojuradoi (Chondrichthyes,Rajidae)

The total lengths (L_T) of 193 males (209–556 mm) and 130 females (275–515 mm) of Amblyraja doellojuradoi, a commercial by‐catch species on the Argentinean continental shelf, which are increasingly retained, were analysed. No sexual dimorphism was observed in the L_T at which 50% of individuals were sexually mature; males matured at 448 mm and females at 411 mm, c. 80 and 82% of maximum L_T. The hepato‐somatic index was similar among sexes, but significantly different between maturity stages, being lower in mature than immature specimens. Males had no seasonal difference in the hepato‐somatic index and females had the lowest index in autumn. The gonado‐somatic index was lower in males than in females and significantly higher in mature than immature specimens of both sexes. Males had the highest index in autumn and females had no seasonal difference. Collectively, these results would indicate that A. doellojuradoi breeds in autumn.     

Lacustrine spawning: is this a new reproductive strategy among ‘large’ African cyprinid fishes?

Changes in the gonado‐somatic index and abundance of the different Labeobarbus species in the mouths of four major afferent rivers of Lake Tana, Ethiopia, were monitored monthly during 1999 and 2000. Riverine spawning was characteristic for seven of Lake Tana's 15 contemporary Labeobarbus species. These seven did not show spatial segregation among afferent rivers but significant temporal segregation occurred in aggregating in the river mouths and migrating towards the upstream spawning areas during the breeding season (June–October). Among the eight other species, peak gonad development occurred generally in the same period as in the riverine spawners. These species, however, did not aggregate in the river mouths during the breeding period and were absent from the upstream spawning areas. A derived, novel strategy, lacustrine spawning was hypothesized for these eight Labeobarbus species. This hypothesis was further supported by observations of running female fishes in the littoral zones distant from any of the afferent rivers. This derived strategy is only common among the littoral‐dwelling Labeobarbus species with restricted distribution patterns. At present it is thought that sequential waves of speciation and habitat divergence followed by trophic specialization, shaped the diversity of Lake Tana labeobarbs.     

Ovarian morphology of the Japanese eel in Mikawa Bay

Annual changes in gonadal maturation of female Japanese eel Anguilla japonica in sea water were investigated histologically over 5 years in the Mikawa Bay, Japan, where they occurred throughout the year except in March. Almost all immature Japanese eels (yellow eels) occurred mainly from April to September, and they were rare after November. In contrast, maturing Japanese eels (silver eels) occurred from October to February. The gonado‐somatic index ( I _G) and oocyte diameters of yellow eels were <1·0 and 150 μm, respectively, and oocytes were at the peri‐nucleolus or the oil droplet stages. The I _G and oocyte diameters of silver eels were greater than those of yellow eels and most oocytes developed to the primary yolk globule stage. The numbers of silver eels lacking oocytes at the primary yolk globule stage increased after January in Mikawa Bay, although I _G and oocyte diameters remained unchanged. In contrast, silver eels caught at the mouth of the bay in January possessed oocytes that had advanced to the secondary yolk globule stage. These observations indicate that oocyte development changes seasonally, especially after winter in Mikawa Bay.     

Enhancement of pH‐resistant iron‐binding activity in supernatants of rainbow trout blood leucocytes by in vitro treatment with phorbol‐12‐myristate‐13‐acetate

Leucocyte lysates from rainbow trout Oncorhynchus mykiss showed an iron‐binding activity that was retained even if the samples were exposed to an acid pH (4·5). Iron‐binding activity of leucocyte supernatants was enhanced by the presence of 1 μg ml⁻¹ phorbol‐12‐myristate‐13‐acetate in the cell medium.     

A monogamous pipefish has the same type of ovary as observed in monogamous seahorses

Syngnathid fish (pipefish and seahorses) are unique among teleost fish in that their ovary consists of a rolled sheet with germinal ridge(s) on the dorsal side running along the entire length of the sheet. A distinct difference is seen in the ovarian structure between polygamous Syngnathus pipefish and monogamous seahorses (Hippocampus spp.), the former having one germinal ridge and the latter with two ridges. This study examined the ovarian structure and the mode of egg production in a monogamous pipefish Corythoichthys haematopterus. The ovary of C. haematopterus had two germinal ridges like that observed in monogamous seahorses. There were two distinct groups of follicles in the ovary, one being a cohort of extremely small follicles and the other a cohort of follicles developing and increasing in size with the passage of time. We suggest that the ovarian structure and the mode of egg production in this pipefish are adaptations to monogamy.     

Reproductive behaviour of the black-striped pipefish Syngnathus abaster (Pisces; Syngnathidae)

The reproductive behaviour of Syngnathus abaster is described and compared with those of other syngnathids. The need for standardized behavioural data is discussed in light of the actual theories of evolution of mating patterns and sex-role reversal within this family.     

Correlates of reproductive success in a wild population of Hippocampus whitei

An analysis of 27 broods born in situ to wild male seahorses Hippocampus whitei , with known partners, showed that female size was the key determinant of the number of young released by the male. There was also an apparent decline in both the number of young per brood, and the size of those young, over the breeding season. The size of the brood and of the young may be more proximate indicators of reproductive success in seahorses than in other fishes, because they can be measured at the time of release, here 20–22 days after fertilization, after which survival is presumed to be relatively higher than in other species. The best model, however, explained <40% of the brood size.     

Occurrence of the parasite Glugea hertwigi in young‐of‐the‐year smelt in Lake Tuusulanjärvi

Young‐of‐the‐year smelt Osmerus eperlanus in Lake Tuusulanjärvi were examined for Glugea hertwigi cysts. Cysts were visible on smelt in the beginning of August and showed a peak at the end of August. Glugea hertwigi may cause mortality among the most heavily infected young‐of‐the‐year smelts.     

Seasonal growth of Atlantic cod: effects of temperature, feeding and reproduction

Growth of 2659 Atlantic cod Gadus morhua aged 4 to 9 years examined in Placentia Bay, Newfoundland, peaked in most cases in June and was at a minimum in October or November. Water temperature, partial fullness index ( I _P) and gonado‐somatic index ( I _G) explained between 31 and 52% of the monthly variability in growth. Temperature and I _P of capelin Mallotus villosus had significant effects on growth of all age groups and explained most of the variance for ages 6–8 and 4–5 years, respectively. The I _P of large invertebrates (ages 4 to 7 years), sandlance ( Ammodytes sp. age 6 years) and demersal fishes (age 9 years) had age‐specific effects in the model. Overall, amphipods, decapods and echinoderms dominated the Atlantic cod diet in most seasons, but fish consumption by Atlantic cod was high in June and July, particularly on capelin. The rapid increase in somatic mass during June and July occurred despite cold water temperatures ( < 3° C at 50 m) and moderate to high gonado‐somatic index. The findings of this study suggest that when food was not a limiting factor, growth tended to increase even when Atlantic cod occupied colder waters, but when food was limiting, the opposite may have occured.     

Life history of an unusual marine fish: survival, growth and movement patterns of Hippocampus guttulatus Cuvier 1829

The life history of the long‐snouted seahorse Hippocampus guttulatus was characterized using mark‐recapture data collected within a focal study site and catch data from 53 additional sites in the Ria Formosa coastal lagoon, southern Portugal. Population structure in benthic habitats was characterized by high local densities (0·3–1·5 m^?2), equal sex ratios and few juveniles <70 mm. Adult H. guttulatus maintained small (19·9 ± 12·4 m²), strongly overlapping home ranges during multiple reproductive seasons. Recruited (benthic) juveniles exhibited significantly lower site fidelity than adults. A Ford‐Walford plot of standard length (L_S) at time t against L_S measured during the previous year from tagged juveniles and adults led to estimates of the von Bertalanffy parameters K = 0·571 and L_∞ = 197·6 mm. The growth rate of planktonic juveniles (inferred from previous studies), was greater than predicted by the von Bertalanffy model, providing evidence of an ontogenetic shift in growth trajectory. The instantaneous rate of natural mortality, M, ranged from 1·13 to 1·22 year^?1(annual survival rate = 29·4–32·2%). Sexes did not differ in movement, growth or survival patterns. On average, H. guttulatus measured 12·2 ± 0·8 mm at birth. Planktonic juveniles recruited to vegetated habitat at 96·0 ± 8·0 mm (0·25 years), had mature brood pouches (males only) at 109·4 mm (0·49 years), began maintaining home ranges and reproducing at 125–129 mm (0·85–0·94 years), and lived for 4·3–5·5 years. Early age at maturity, rapid growth rates, and short generation times suggested that H. guttulatus may recover rapidly when direct (e.g. exploitation) and indirect (e.g. by‐catch and habitat damage) effects of disturbance cease, but may be vulnerable to extended periods of poor recruitment.     

Reproductive biology of female Amazonian brocket deer in northeastern Peru

The aim of this study was to provide information on the reproductive biology of brocket deer. Hence, we analyzed female reproductive tracts collected by rural hunters from 1991 to 1998 in the Tamshiyacu-Tahuayo Communal Reserve, northeastern Peruvian Amazon. We characterized the basic reproductive biology of brocket deer, analyzed whether the distributions of conceptions and births are aseasonal, and compared their reproductive productivity in two different areas subject to heavy and slight hunting pressures, respectively. We found that: (1) red and gray brocket deer did not differ in ovulation, fertilization, and pregnancy rates; (2) average number of fetuses per birth was 1.2 for red brocket deer and one for gray brocket deer; (3) sex of fetuses suggests a male biased sex ratio for both species; (4) neither species shows reproductive seasonality; and (5) gross productivity does not differ between heavily and slightly hunted areas. Our results indicate that brocket deer exhibit reproductive characteristics similar to their conspecifics in other parts of their native distribution range.     

Short‐term survival and movements of Atlantic sharpnose sharks captured by hook‐and‐line in the north‐east Gulf of Mexico

Ultrasonic telemetry was used to compare post‐release survival and movements of Atlantic sharpnose sharks Rhizoprionodon terraenovae in a coastal area of the north‐east Gulf of Mexico. Ten fish were caught with standardized hook‐and‐line gear during June to October 1999. Atlantic sharpnose sharks were continuously tracked after release for periods of 0·75 to 5·90 h and their positions recorded at a median interval of 9 min. Individual rate of movement was the mean of all distance and time measurements for each fish. Mean ± s.e . individual rate of movement was 0·45 ± 0·06 total lengths per second (L_T s^?1) and ranged from 0·28 to 0·92 L_T s^?1 over all fish. Movement patterns did not differ between jaw and internally hooked Atlantic sharpnose sharks. Individual rate of movement was inversely correlated with bottom water temperature at capture (r² = 0·52, P ≤ 0·05). No consistent direction in movement was detected for Atlantic sharpnose sharks after release, except that they avoided movement towards shallower areas. Capture‐release survival was high (90%), with only one fish not surviving, i.e. this particular fish stopped movement for a period of 10 min. Total rate of movement was total distance over total time (m min^?1) for each Atlantic sharpnose shark. Mean total rate of movement was significantly higher immediately after release at 21·5 m min^?1 over the first 1·5 h of tracking, then decreased to 11·2 m min^?1 over 1·5–6 h, and 7·7 m min^?1 over 3–6 h (P ≤ 0·002), which suggested initial post‐release stress but quick recovery from capture. Thus, high survival (90%) and quick recovery indicate that the practice of catch‐and‐release would be a viable method to reduce capture mortality for R. terraenovae.     

Fish drift in a Danube sidearm‐system: I. Site‐, inter‐ and intraspecific patterns

A total of 10 649 larval and juvenile fishes of 24 species were caught in the drift at Marchfeldkanal, a man‐made side branch of the Danube River near Vienna, Austria, with tubenose goby Proterorhinus marmoratus being the dominant species. Distinct differences in inter‐ and intraspecific drift patterns among different sampling stations along the course of the channel were found. The percentage of the rheophilic and rheoparous ecological guild was highest at the inlet of the channel, where it is directly fed with water from the Danube. For individual species, significant differences in drift densities among sites were found for tubenose goby, barbel Barbus barbus , ide Leuciscus idus , roach Rutilus rutilus and for the two most abundant percids, the pike‐perch Sander lucioperca and zingel Zingel zingel combined. The occurrence of larval and juvenile fishes in the drift was related to certain developmental stages and differed between species and sites. Most species (common bream Abramis brama , bleak Alburnus alburnus , gudgeon species Gobio spp., chub Leuciscus cephalus , ide and roach) occurred with highest densities at the earliest developmental larval stage, but some species ( e.g . common bream and roach) were also found abundantly in drift at later developmental stages. Application of Ivlev's index of electivity as a drift index describing the propensity of the different species to drift, yielded the highest indices for the gudgeon species, common bream and bleak and the lowest for perch Perca fluviatilis , Prussian carp Carassius auratus gibelio and rudd Scardinius erythrophthalmus .     

A comparison of the maturation and growth of female flathead sole in the central Gulf of Alaska and south‐eastern Bering Sea

Female flathead sole Hippoglossoides elassodon maturity appears not to be area dependent since the total length ( L _T) at which 50% were mature ( L _T50) was similar for the central Gulf of Alaska (333 mm) and south‐eastern Bering Sea (320 mm) areas. Likewise the age at which 50% were mature ( A ₅₀) was similar in the south‐eastern Bering Sea (9·7 years) and central Gulf of Alaska (8·7 years). The timing of female flathead sole spawning may also be similar between areas. Batch or serial spawning was indicated for flathead sole. Female flathead sole grew at a similar rate in both the Gulf of Alaska and Bering Sea. In contrast, males grew faster in the Bering Sea than in the Gulf of Alaska. Males grew more slowly than females in both areas after 5 years of age, and reached a smaller maximum L _T. The growth of both sexes was similar during 1993 and 1996 in the Gulf of Alaska.     

Reproductive biology of Psammobatis extenta

Psammobatis extenta collected from the commercial bottom trawl fishery operating in Puerto Quequén, Argentina, between 2000 and 2001, had a sex ratio of 1:1 (535 specimens). Both the largest male and female measured 313 mm total length ( L _T). The relationship between total body mass and L _T was significantly different between sexes; mature females weighed more than mature males for a given L _T. The size at which 50% of males were sexually mature was 262 mm L _T (83·6% of the maximum size), whereas 50% of females were mature at 249 mm L _T (80·0% of the maximum size). The gonadosomatic index in mature males and females was slightly higher during summer, but did not show significant variation over the sampling period. The hepatosomatic index of males and females was higher during the autumn and winter and followed a distinct seasonal pattern. Evidence suggested a continuous reproductive cycle during the year, with a maximum number of females carrying egg-cases in summer.     

Reproductive biology of Clintonia udensis

To clarify the life history of Clintonia udensis, we investigated its reproductive systems and spatio‐temporal population structure. Pollination experiments and the observation of floral visitors revealed that C. udensis was compatible with both self‐ and outcross‐pollen, and it potentially produces seeds by insect‐mediated outcrossing in natural conditions. In addition, propagation by clonal reproduction from rhizomes was evident. In this study, it was clarified that C. udensis potentially propagates by sexual and asexual reproduction and maintains its population through a stable frequency of flowering. The differences in the dependence on each reproduction mode could be one of the contributing factors for creating a variety of population sizes and distribution patterns of ramets in populations.     

Reproductive biology and egg mortality of bay anchovy, <Emphasis Type="Italic">Anchoa mitchilli</Emphasis>, in the Hudson River estuary

Synopsis Bay anchovy, Anchoa mitchilli, is an ecologically important species in coastal systems, acting as predators on zooplankton while serving as prey for many birds and economically important finfish species. Despite the importance of bay anchovy, limited information exists concerning reproductive biology and egg mortality from the northern parts of its range. Spawner demographics suggested Hudson River fish were older and larger than reported elsewhere. Egg mortality rates were higher in the Hudson River than reported in more southerly systems. Differences in the reproductive biology of bay anchovy suggest either anthropogenic factors or latitudinal differences between populations exist and therefore should warrant further investigations on this species in the northern portions of its range