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1.
Fecundity of female rock lobster Jasus lalandii was studied in order to examine whether regional differences existed along the west coast of South Africa, where growth rates (at least of males) were known to vary considerably. The study, in August/September 1985, included all major rock-lobster Fishing grounds from Port Nolloth in the north to Olifantsbos on the Cape Peninsula in the south. Earlier studies showed that growth rates of adult rock lobsters are fast in areas where per capita food availability is high (the south-central region of the West Coast), whereas growth rates were slower where food supplies are limited. The results presented indicate that fecundity of females is also higher in areas where growth rates of males are fast. Year-to-year variations in fecundity of females may possibly be an indicator of growth rates of adult rock lobsters.  相似文献   

2.
Indicators of abundance for American lobster (Homarus americanus) based on 8 years of trap catch rates (catch‐per‐unit‐effort, CPUE) were evaluated. Volunteer harvesters recorded count, sex and size of lobsters captured in standard traps on a daily basis during the fishing season in coastal Nova Scotia, Canada. We examined the extent to which standardised CPUEs of prerecruits predict the future catches of legal sizes and explored spatial patterns in the abundance of lobsters of different size and reproductive status. The standardised CPUE of prerecruits was correlated with legal size catches in only one of five areas examined. This area had a strong signal of incoming recruitment. Improving the capacity of prerecruit CPUE for predicting legal size catches several years later most likely lies with model incorporation of variables associated with catchability. The spatial distribution of catch rates showed that the area with the highest historical landings per unit area also had the highest relative abundance of prerecruits. The spatial distribution data point to further areas of research related to recruitment processes in lobster in coastal Nova Scotia.  相似文献   

3.
Post‐puerulus specimens of Jasus edwardsii (Hutton) have been successfully reared in the laboratory from the puerulus stage for periods of up to 12 months. The spiny lobsters were reared in concrete‐asbestos tanks measuring 2.4m × 37cm × 23cm. The tanks were supplied with a continuous flow of sea water and provided with constant aeration. Empty shells of paua (Haliotis iris Martyn) and rocks from the intertidal zone provided cover within the tanks.

Fresh mussel (Mytilus sp.) was preferred to all other foods tried in feeding experiments. The animals were fed every second day on opened mussels, and occasionally on fresh fish. The juveniles “grazed” actively on the calcareous algae (Corallina officinalis L.) present on the rocks.

The animals were extremely sensitive to pollution. To reduce pollution risks all sediments were removed from each tank, as the interstices between them were found to harbour uneaten food particles. Any uneaten foods were siphoned out every second day and each tank was thoroughly cleaned every six to eight weeks.

From a total of over 3,300 animals collected since November 1965, over 800 are presently being reared in the laboratory and various aspects of their ecology studied. The first step in raising larger adult sizes from juvenile stages in the laboratory is clearly possible.  相似文献   

4.
Information on life cycle strategies and reproductive parameters of Metridia pacifica is scarce, despite its importance in the zooplankton of the subarctic Pacific. In many regions it occurs in high abundance, but reproductive rates, when reported, are usually low. This discrepancy was studied in Dabob Bay, Washington, USA, in the context of an investigation of the effect of diatom blooms on the reproductive success of copepod grazers.In situ egg production rates of M. pacifica were measured in spring and mid-summer with standard methods (multi-wells) and a new incubation chamber (spawning towers) that separates the spawning female from its eggs and allows the eggs to develop undisturbed. Many females did not produce eggs, possibly due to a high fraction of immature individuals. Egg production rates were variable, but clutch sizes were higher in spawning towers, and estimates of female egg cannibalism revealed that females consume many eggs shortly after their release. Thus, a separation of females and eggs is mandatory for accurate measurements of M. pacifica egg production rates. The maximum clutch sizes recorded in our study were comparable to measurements for other calanoids. However, unviable eggs were a large fraction of those spawned, independent of incubation method, especially in late winter and early spring. In order to assess whether the diatom effect may be responsible for low viability of embryos and nauplii, we also measured in situ grazing. Adult females were omnivorous, but they ingested some diatoms that rank among the strongest anti-mitotic toxin producers known so far. Although M. pacifica’s vertical migration behavior suggests opportunistic feeding on abundant food during their short stay in the phytoplankton-rich surface, they often ignored the food items that contributed most to microplankton carbon concentrations. Thus, their feeding strategy remains ambiguous. Due to severe reproductive failure early in the season, recruitment was impaired in spring, while the population increased, reaching high abundance in mid-summer when reproductive output was low. While advection and interannual variability in bloom conditions might compensate for the losses described here, the paradox of high Metridia abundance versus low reproductive success still requires further investigation, and methodological constraints need to be ruled out in future studies.  相似文献   

5.
Pseudunciola obliquua is the most abundant subtidal amphipod of the near-shore macrobenthos in the New York Bight south of Fire Island. It has an annual life-cycle. Breeding occurs in March and April, and a single brood of between 8 and 20 eggs per female is produced. Fecundity is linearly proportional to maternal length. The eggs take about two months to develop; the juveniles emerge in June and July. Initial recruitment in the study area was estimated to be 2980 and 5850 per m2 for the 1979–1980 and 1980–1981 year classes, respectively. Of the initial recruits only about 10% survive to form the reproductive stock of the following spring.Females and males grow at similar rates and are equally abundant as juveniles and initially as adults, until they reach sexual maturity. After breeding, the abundance of males decreases rapidly due to post-reproductive death. Females continue to live, carrying the developing eggs in their brood pouches. Mean female growth increases throughout the brooding period until the young are released, shortly after which adult females also die. The entire generation of reproductive adults has died by September.  相似文献   

6.
Population biology of the amphipod Ischyrocerus commensalis Chevreux, 1900, a facultative commensal of the red king crab Paralithodes camtschaticus (Tilesius, 1815), is here described on samples collected during summers 2005–2009 in Dalnezelenetskaya Bay (Southern Barents Sea, Russia). The studied features included infestation indices, size composition, morphometric, and reproductive parameters of the summer generation. During the studied period, prevalence and mean number of I. commensalis per host were 34.4% and 54.4 ± 3.3 individuals, respectively. The majority of amphipods were found on the host mouth parts, limbs, and gills. The amphipod sex‐ratio was significantly biased towards females (F:M = 1.36:1). The size frequency distributions observed in July and August were similar but in July the proportion of the smallest amphipods (<2.1 mm body length) was two times higher than that in August. All the amphipods with body length >5.1 mm were males or females. Length–weight relationships in female and male amphipods differed significantly, suggesting that females were heavier than the same‐sized males. The females carrying eggs in their brood pouches were the most abundant groups (54.8% in July 2009 and 51.6% in August 2005–2008). The minimal body length of a female which had released juveniles was 7.0 mm in July and 6.2 mm in August. The size at 50% maturity of I. commensalis females was estimated to be 6.58 mm. The number of eggs laid is positively linearly correlated with the size of a female. The proportion of the females with eggs in the latest developmental stage in July was 10 times higher than in August. The differences of biological features in symbiotic amphipods between the July and August may be explained by more intensive reproduction effort in the earlier month.  相似文献   

7.
Eggs were separated from the setae of berried female rock lobsters (Jasus edwardsii) by soaking in 1 N KOH for 6–12 h. This technique separated almost all of the eggs from the setae and each other with minimal damage. An electronic egg‐counter incorporating a phototransistor was used to count the eggs suspended in water. It had a high degree of accuracy (C.V.= 1.5%) when eggs were counted at a rate of about 200 000 per hour.  相似文献   

8.
Green (spiny) lobsters Panulirus regius were obtained by diving at Cape Verde, West Africa, during three sampling periods: May–November 2001, April–December 2002 and April–June 2003. Totals of 429 male lobsters and 423 females (852 in all) were caught. Half the females were ovigerous throughout the sampling periods. Female estimated size-at-50% maturity was 87.9mm carapace length (CL). Brood size and egg developmental stage were examined in 68 ovigerous females. The relationship between brood size (BS, thousands of eggs) and CL (mm) was BS = 1.59CL2.77. Females in the size-class 100–105mm and 115–120mm CL produced half the eggs in the population. Based on these results, an increase in the minimum landing size is proposed. The potential implementation of a maximum landing size is discussed.  相似文献   

9.
Captive rock lobsters (Jasus edwardsii) were able to open and eat live dredge oysters (Ostrea lutaria) by progressively breaking away the shell edges with the mandibles and walking legs. Oysters are probably of only slight significance in the natural diet of rock lobsters.  相似文献   

10.
In the North Cape area (34°26'S, 173°07'E) there appears to be a concentration of late juvenile packhorse rock lobsters, Jasus verreauxi (H. Milne Edwards'), which subsequently contributes significantly to the nearby fishery for adult J. verreauxi off Cape Reinga. Evidence for this is based on the overall smaller size and fewer mature rock lobsters at North Cape compared to areas nearby, and on the results of tagging experiments carried out during 1976–77. Rock lobsters tagged at North Cape moved 21–514 km, mainly west and south, before recapture at minimum rates of 0.03–2.00 krn.d‐1. For females at least, the movement away from North Cape usually occurs at about the time that sexual maturity is attained. Rock lobsters tagged near Cape Reinga moved 3–34 km west at minimum rates of 0.04–0.35 km.d‐1.

Although the closure of the North Cape grounds to rock lobster fishing restricts the taking of the small number of legal‐sized fish available in the area, the restriction ensures less mortality and damage to the undersized fish due to handling.  相似文献   

11.
This study provided the first comprehensive analysis of Atlantic horseshoe crab (Limulus polyphemus) fecundity. Limulus appear to be a determinate spawner, maturing all eggs for the breeding season before spawning begins. On average, larger females held a larger number of eggs (63,500) than smaller females (14,500). By the end of the breeding season there was an average of 11,600 mature eggs per female left undeposited, regardless of female size. Larger females laid a higher percentage of the eggs they contained. Thus they not only contain more eggs, but are more effective at laying them as well. Size of spawning females ranged from about 185–300 mm prosomal width, with by far the highest concentration in the mid‐size ranges. Although on an individual basis large females carry and lay the greatest number of eggs, mid‐size crabs as a group contributed more to the horseshoe crab population in Pleasant Bay because they were more plentiful (net fecundity was highest for mid‐size crabs). These results have implications for the management of this important species, which is harvested for bait, scientific, and biomedical uses. Incorporation of these results into models and other management tools can help predict growth rates, effects of size‐selective harvest, reproductive value, and stable stage distribution of populations.  相似文献   

12.
Abstract. The breeding biology of the cave-dwelling Mediterranean triplefin blenny Tripterygion melanurus (Pisces, Blennioidei) was studied in the field. Two types of reproductive male were observed, territorial males and non-territorial males. Territorial males establish territories for mating, but not necessarily for feeding, in caves and crevices at depths between 0.5 and 33  m. Territories can be settled in clusters in a single cave. Non-territorial males occur in the vicinity of territories and attempt to parasitise matings of territorial males. Gravid females wait near territories where another female is spawning, rather than spawn with currently unmated territorial males. Waiting females intrude in matings and sometimes displace a spawning female. The frequency of mating of the territorial male, of sneaking and of female intrusions are higher in territories that border others than in isolated territories. Females may minimise predation risks both on themselves and on their eggs by spawning in clustered territories and by spawning with males that have more than one clutch of eggs. Territorial males must find a compromise between the benefits of attracting a female and the costs of parasitic spawning by sneaker males. The possibility that territorial males tolerate the proximity of other territorial males and accept a risk of cuckoldry is discussed. Parasitic spawning in T. melanurus is relatively rare and the gonadosomatic index in both non-territorial and territorial males is low, indicating that sperm competition is probably not intense.  相似文献   

13.
Octopus magnificus is a regular bycatch of traps set for spiny lobsters and bottom trawls for Cape hakes Merluccius spp. on the continental shelf of South Africa. Octopuses were collected from rocky substrata (traps) and soft sediments (research trawls) during a three-year period (2002–2005) and over a wide geographical and depth range to investigate their basic biological and life-history characteristics. Octopuses collected from trawl nets were smaller than those from traps. Males from traps and trawl nets were larger than females, with males being more frequently caught in traps than females. Size distributions were seasonally cyclical, increasing from a small mean size in the austral winter to a peak in summer, and receding during autumn. No mature females were found on soft sediments. The female gonadosomatic index peaked during summer, and sperm were found in oviducts year-round. Males reached 50% maturity at a weight of 4.6kg compared with 5.8kg in females. Mature females produced up to 10 000 medium-to-large (4–9mm maximum length) eggs, and potential fecundity was positively related to female body and ovary weight. Feeding rates were highest in trap-caught octopuses and gut contents consisted mainly of bait, spiny lobsters and teleosts (mainly jacopever Helicolenus dactylopterus). The gut contents of trawl-caught octopuses consisted mainly of crustaceans (84%), mostly portunid crabs but no spiny lobsters, teleosts (15%) and molluscs (1%). The results suggest that O. magnificus has a short (c. 1 year) lifespan, with winter/spring recruitment, a summer spawning peak, and post-spawning mortality in autumn. Alternatively, the species may have a longer lifespan with seasonal migrations between rocky and soft substrata.  相似文献   

14.
Reproductive patterns of an epifaunal amphipod,Pontogeneia rostrata, were studied on Dolsando sandy shore in Korea. The life history pattern was iteroparous, with recruitment mainly occurring from winter to spring. The sex ratio was male-biased, especially during breeding periods. The mean body length of females was significantly larger than that of males. Brood size and egg volume were positively related to the body length of ovigerous females. There was no significant difference in brood size between successive breeding periods, but egg volumes were significantly higher in early winter (December) than in late spring breeding (May and June), increasing the probability of survival to hatching. These traits contribute to more reproductive potential in early winter than in late spring breeding. The mean brood size of epifaunalP. rostrata was larger but the mean egg volume smaller than that of infaunal amphipods in this sampling area. We suggest that reproductive effort for epifaunal species may be proportionally greater than for infaunal species in risky environments.  相似文献   

15.
Pleuroncodes monodon is an important fishery resource and key species from the Southeastern Pacific. During its prolonged reproductive period (from February to December), ovigerous females are exposed to seasonal variation in environmental factors (e.g. temperature and food availability), with higher levels of these environmental parameters during summer and lower in winter, and must adjust their biochemistry to ensure their own survival and that of their embryos. The aim of this study was to analyse seasonal changes in the biochemical composition of ovigerous females and their eggs. The data show that the content of lipids, proteins and organic matter in the hepatopancreases of females was significantly higher in winter than in summer. Similarly, the lipid content of the eggs was significantly higher in winter than in summer, yet the protein content of the eggs had the opposite pattern with greater values found in summer. Consistent with the ‘reproductive energetic model’, the initial and final energy produced by the hepatopancreas showed significant seasonal variations, whereas female investment in egg production (in absolute values) did not show significant seasonal differences. The seasonal differences observed in the biochemistry, organic matter and energy content of the female hepatopancreases may be related to the storage of energy for growth and reproduction. Furthermore, the seasonal variation in the content of lipids, proteins and energy in eggs is likely related to embryogenesis and larval hatching in function with environmental conditions. Seasonal variation in the biochemical composition of P. monodon has direct effects on the marine food web and also upon fisheries.  相似文献   

16.
Caribbean spiny lobster (Panulirus argus) settle preferentially in macroalgal‐covered hard‐bottom habitat, but seagrass is more prevalent in Florida (United States) and the Caribbean, so even low settlement of lobsters within seagrass could contribute substantially to recruitment if post‐settlement survival and growth were high. We tested the role of seagrass and hard‐bottom habitats for P. argus recruitment in three ways. We first explored possible density‐dependent regulation of early benthic juvenile lobster survival within cages deployed in seagrass and hard‐bottom habitats. Second, we compared settlement and survival of P. argus in both habitats, by comparing the recovery of microwire‐tagged early benthic juveniles from patches of seagrass and hard‐bottom. Finally, we assessed the relative abundance of juvenile lobsters in each habitat by deploying artificial structures in seagrass sites and compared these data with data from similar deployments of artificial structures in hard‐bottom habitat in other years. More early benthic juvenile lobsters were recovered from cages placed in hard‐bottom than in seagrass, but mortality of the early benthic life stage was high in both habitats. In regional surveys, the mean number of lobsters recovered from artificial shelters deployed within seagrass was lower than in any year that we sampled hard‐bottom, indicating that fewer lobsters reside naturally in seagrass, particularly large juveniles >40 mm carapace length. The greater abundance (and likely survival) of juvenile P. argus that we observed in hard‐bottom habitat as opposed to seagrass, combined with previous studies demonstrating that postlarval P. argus are attracted to, settle in, and metamorphose more quickly in red macroalgae, confirm that macroalgae‐dominated hard‐bottom habitat appears to be the preferred and more optimal nursery for Caribbean spiny lobster.  相似文献   

17.
We have studied two congeneric limid bivalves, Acesta species novum and Acesta excavata (Bivalvia: Limidae), that live in similar physical conditions but use different food sources. Acesta sp. nov. live on the giant siboglinid tubeworm Lamellibrachia luymesi at cold seeps and feed on their eggs, a continuous food source that ultimately is derived from chemosynthesis, whereas A. excavata relies on planktonic food of photosynthetic origin, which varies seasonally. We hypothesized that these two species might show differences in the periodicity of reproduction; specifically, we predicted that A. sp. nov. would breed continuously and that A. excavata would demonstrate an annual reproductive cycle. Our hypothesis was refuted, as both species have a semi‐continuous reproductive cycle. Food quality, quantity or seasonality had no clear effect. Reproductive adults are functionally gonochoristic. Females broadcast buoyant eggs with an average size of 179 μm in A. sp. nov. and 160 μm in A. excavata. Both the size of the larval shell and the size of the spawned eggs are suggestive of pelagic lecithotrophic development. Both species also appear to be protandric hermaphrodites, changing from male to female at approximately 77 and 90 mm shell height, respectively, although not all individuals change sex. In the material investigated in this study there was a biased sex ratio favouring males.  相似文献   

18.
The reproductive cycle of the dwarf oyster Ostreola stentina (Payraudeau 1826) at Monastir in the south of the Gulf of Hammamet on the east coast of Tunisia was studied using condition indices and histological techniques. The species was shown to be a protandric hermaphrodite. Whereas males dominated the small shell length categories (12.45–34.99 mm), females (21.00–47.16 mm) and hermaphroditic individuals (30.00–57.95 mm) become more predominant with increasing size, suggesting that individuals may undergo protandric development. The overall male to female ratio was 1.0:1.7. Gametogenic development begins in February–March for females and in September for males, and spawning occurs during April and July for females and December and July for males. There was a clear relationship between the gonadal condition index and gametogenic stage for both sexes. Values increased from zero in their early stage of development and peaked during ripe and spawning stages, before decreasing in the spent stage. However, the meat condition index did not show any statistical differences between gametogenic stages.  相似文献   

19.
Heterocarpus ensifer is a tropical deep-water pandalid shrimp whose reproductive features are poorly known. We examined reproductive traits of a population of H. ensifer inhabiting the continental slope (311–715 m in depth) off the Yucatan Peninsula, Mexico (SW Gulf of Mexico). Size range of the total sample (n=816) was 10.4–38.9 mm carapace length. Females grow larger than males, but both sexes mature at 57% of their maximum theoretical size and at ～30% of their total lifespan. Among adult females, the proportion of ovigerous females was high in all seasons, indicating year-round reproduction. Most females carrying embryos in advanced stages of development had ovaries in advanced stages of maturation, indicating production of successive spawns. In the autumn, however, the proportion of ovigerous females and the condition index of these females were lower compared to other seasons. This pattern potentially reflects a reduction in food resources following the summer minimum in particulate organic carbon flux to the deep benthos, as reported in previous studies. Spawns consisting of large numbers (16024±5644, mean±SD) of small eggs (0.045±0.009 mm3) are consistent with extended planktotrophic larval development, an uncommon feature in deep-water carideans. Egg number increased as a power function of female size but with substantial variability, and egg size varied widely within and between females. There was no apparent trade-off between egg number and egg size and neither of these two variables was influenced by female condition. These results indicate iteroparity and a high and variable reproductive effort, reflecting a reproductive strategy developed to compensate for high larval mortality. The present study provides a baseline to compare reproductive traits between Atlantic populations of this tropical deep-water pandalid.  相似文献   

20.
Fecundity in Jasus verreauxi (H. Milne Edwards, 1851) has been studied by a detailed investigation of (a) the total weight of eggs carried by female specimens, (b) the average number of eggs per 1 g sample, and (c) the total number of eggs carried by females. In mid October 1966, 217 females “in berry” (that is, carrying external eggs) were examined and measured at Spirits Bay, New Zealand. The fecundity study is based on the results obtained from 21 selected specimens, with carapace lengths from 15.5 cm to 23.5 cm.

A direct relation was found between the total weight of eggs carried and increase in carapace length. The total weight of eggs carried varied from about 51 g to 238 g for carapace lengths of 15.5 cm to 23.5 cm. No correlation was shown between the average number of eggs per 1 g sample and increase in carapace length. Considerable variation was noted in the number of eggs per 1 g sample, which ranged from a low count of 6,453 eggs to a high count of 8,341 eggs. The total number of eggs carried by female J. verreauxi was found to be related to an increase in carapace length. Furthermore, increase in fecundity per relative carapace length increase was noted to be greater in smaller specimens than in larger specimens. The total number of eggs carried ranged from about 385,000 for a carapace length of 15.5 cm to 1,940,000 for a carapace length of 23.5 cm.

Fecundity, as measured by the total weight of eggs carried and the total number of eggs produced, was found to be much higher in J. verreauxi than in several Jasus species previously studied by other workers.  相似文献   

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