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1.
The association between planktonic larval and benthic stages of Manila clam Ruditapes philippinarum and factors determining successful recruitment were studied in Akkeshi-ko estuary and Akkeshi Bay, Hokkaido, northern Japan. The field study showed that planktonic larvae were localized mainly in the bay after dispersal from the estuary and recruitment to the estuarine fishing grounds was not always successful. A numerical analysis suggested that estuarine circulation transported tracers, used to simulate planktonic larva, from the estuary to the bay but the number of returning tracers varied depending on the river discharge and wind direction. The planktonic larvae were affected by unsuitable conditions for survival in the estuary, such as high turbidity. We conclude that most larvae develop within the bay, where conditions are more saline and less turbid, and that although return to the estuary is essential for recruitment, it is not necessarily related to the abundance of larvae. 相似文献
2.
SEM observations on larval shell morphology of Manila clam Ruditapes philippinarum and their utility
Nariaki Inoue Ryogen Nanbu Natsuki Hasegawa Junya Higano Hisami Kuwahara Hideo Sekiguchi 《Fisheries Science》2012,78(6):1237-1243
Manila clam Ruditapes philippinarum is common and abundant on Japanese tidal flats, forming a commercially important clam fishery. However, annual catches of Manila clam have decreased drastically since 1975?C1985. To study larval recruitment processes of Manila clam, we carried out scanning electron microscopy (SEM) observations on larval and juvenile shells of clams reared at 20 and 24?°C. There was no significant difference in final shell length of trochophores between 20 and 24?°C. However, the larval duration was much longer and the shell length of settled size of pediveligers was much larger for clams reared at 20?°C than those reared at 24?°C. These findings suggest that larval duration and growth, as well as settlement size, may vary markedly depending on temperature (and probably on season). The larval shell morphology of Manila clam can provide essential information about larval recruitment processes. 相似文献
3.
The ultimate goal of early life studies of fish over the past century has been to better understand recruitment variability. As evident in the Georges Bank haddock (Melanogrammus aeglefinus) population, there is a strong relationship between recruitment success and processes occurring during the planktonic larval stage. This research sought new insights into the mechanisms controlling the recruitment process in fish populations using biological–physical modeling methods together with laboratory and field data sets. We created the first three‐dimensional model of larval haddock on Georges Bank by coupling models of hydrodynamics, lower trophic levels, a single copepod species, and larval haddock. Interactions between feeding, metabolism, growth, vertical behavior, advection, predation, and the physical environment of larval haddock were quantitatively investigated using the coupled models. Particularly, the model was used to compare survival over the larval period and the sources of mortality in 1995 and 1998, 2 years of disparate haddock recruitment. The results of model simulations suggest that the increased egg hatching rates and higher food availability, which reduced starvation and predation, in 1998 contributed to its larger year‐class. Additionally, the inclusion of temperature‐dependent predation rates produced model results that better agreed with observations of the mean hatch date of survivors. The results from this biophysical model imply that food limitation and its related losses to starvation and predation, especially from hatch to 7 mm, may be responsible for interannual variability in recruitment and larval survival outside of the years studied. 相似文献
4.
Samples of Manila clam (Ruditapes philippinarum Adams & Reeve 1850) were collected from May 2004 to April 2005 monthly, and plankton net trawling of planktonic larvae and bottom sediment sampling surveys were further conducted from May to October 2006 in Jiaozhou Bay. Based on the data collected, growth, mortality and reproduction of the transplanted Manila clam and the environmental effects were examined. The results showed that the enhanced clams grew well and showed a growth trend similar to the local wild ones. The main growth periods lasted from April to September, with the water temperature being the main factor affecting the growth, which was the same as that of the wild clams. There were also two reproduction cycles for the farmed Manila clams each year in Jiaozhou Bay and the main breeding period was from May to June. The phenomenon of delayed metamorphosis was quite common through larval development. The farmed clams could spawn when they reached sexual maturity, but they could not perform effective recruitment as many planktonic larvae died during metamorphosis and settlement. A preliminary study indicated that sediment perturbation and marine environment pollution were the main factors causing the death of larvae in the development process. 相似文献
5.
Go Suzuki Seiji Arakaki Kiyoshi Suzuki Yukihiro Iehisa Takeshi Hayashibara 《Fisheries Science》2012,78(4):801-808
In situ larval seeding is a low-cost technique that is currently under development for the large-scale restoration of coral populations. One problem that still needs to be solved is the preparation of coral larvae for seeding, i.e., how many larvae are required to restore a certain area? In this study, we focused on the relationship between the numbers of larvae, settlers, and survivors for three?months post-settlement to determine the optimal larval seeding density. A comparison of three different larval densities (low, middle, and high) indicated that the number of settlers was proportional to the larval density, suggesting that settler density is determined by the number of larvae supplied. However, the survival rate of settlers on high-density plates was much lower than the corresponding rates on low- or middle-density plates during the first month after settlement. Moreover, most of the seeded corals had not survived on the low-density plates at three?months after settlement. Therefore, the middle larval density (i.e., 5000?larvae?m?2) appears to be optimal for seeding on grid plates. 相似文献
6.
Variability in the high mortality rate during early life stages is considered to be one of the principal determinants of year‐class variability in fish stocks. The influence of water column stability on the spatial distribution of fish larvae and their prey is widely acknowledged. Water column stability may also impact growth through the early life history of fishes, and consequently alter the probability of survival to maturity by limiting susceptibility to predation and starvation. As a test of this concept, the variability in condition and growth of dab (Limanda limanda) and sprat (Sprattus sprattus) larvae was investigated in relation to seasonal stratification of the water column in the north‐western Irish Sea. RNA/DNA ratios and otolith microincrement analysis were used to estimate nutritional status and recent growth rates of larvae captured on four cruises in May and June of 1998 and 1999. Dab and sprat larvae were less abundant in 1999 and were in poorer condition with lower growth rates than in 1998. Dab larvae of <13 mm also exhibited spatial variability with higher RNA/DNA ratios at the seasonal tidal‐mixing front compared with stratified and mixed water masses. However, the growth and nutritional status of sprat larvae was uncorrelated to water column stability, meaning the more favourable feeding conditions generally associated with the stratified pool and tidal‐mixing front in the Irish Sea were not reflected in the growth and condition of these larvae. This suggests that the link between stability, production and larval growth is more complicated than inferred by some previous studies. The existence of spatio‐temporal heterogeneity in the growth and condition of these larvae has implications for larval survival and the recruitment success of these species in the Irish Sea. 相似文献
7.
8.
H. William Fennie Noah Ben-Aderet Steven J. Bograd Garfield T. Kwan Jarrod A. Santora Isaac D. Schroeder Andrew R. Thompson 《Fisheries Oceanography》2024,33(2):e12658
Identifying factors that affect larval mortality is critical for understanding the drivers of fish population dynamics. Although larval fish mortality is high, small changes in mortality rates can lead to large changes in recruitment. Recent studies suggest maternal provisioning can dramatically affect the susceptibility of larvae to starvation and predation, the major sources of early-life mortality. We measured otolith core width-at-extrusion and validated that this is a proxy for larval size-at-extrusion for eight species of rockfishes (genus Sebastes) to examine the influence of initial larval size on larval growth and survival and to understand how oceanographic conditions experienced by gestating females affect larval size (i.e., quality). Otolith core width-at-extrusion was significantly positively related to larval rockfish recent growth rate (5/7 species with sufficient sample size) and survival (all eight species). This suggests that individuals that are larger at extrusion generally grow faster and are more likely to survive early life stages. Otolith core width-at-extrusion was positively related to higher presence of Pacific Subarctic Upper Water and was negatively related to warmer, saline waters at the depths gestating mothers inhabited during the months prior to larval collection. In addition, otolith core width was larger further from fishing ports, possibly because these locations were historically less fished, contained more older, larger females, and/or had inherently better habitat quality (higher Pacific Subarctic Upper Water) than sites closer to shore. These results indicate that the environmental conditions female rockfish experience during gestation drive the size of the larvae they produce and impact larval growth and survival. 相似文献
9.
Toshinori Takashi Hirotoshi Kohno Wataru Sakamoto Shigeru Miyashita Osamu Murata & Yoshifumi Sawada 《Aquaculture Research》2006,37(12):1172-1179
Diel and ontogenetic changes in larval body density related to swim bladder volume were investigated in Pacific bluefin tuna, Thunnus orientalis, to determine the causality of larval mortality – adhesion to the water surface and contact with the tank bottom during seedling production. The density of larvae with deflated swim bladders increased with total length and days post hatch. Diel density change was observed after day 2 post hatch; owing to daytime deflation and night‐time inflation of the swim bladder, the density was relatively higher during the daytime. Increased swim bladder volumes clearly reduced larval density during the night‐time after day 9 post hatch. However, the density of larvae with inflated swim bladders was greater than rearing water density (Δρ>0.0099). The small density difference between larvae and rearing water (Δρ=0.0022?0.0100) until day 4 post hatch may have caused larval mortality by adhesion to the water surface because larvae can be easily transported to the water surface by aeration‐driven upwelling in rearing tanks. Density increased noticeably from day 5 to day 9 post hatch. The increased density difference (Δρ=0.0065?0.0209) in larvae and rearing water possibly induced mortality by contact with the tank bottom because larvae sink particularly during the night‐time on ceasing swimming. 相似文献
10.
Fish eggs and larvae are often subject to very high mortality, and variation in early life survival can be important for population dynamics. Although longnose suckers (Catostomus catostomus) are widespread in northern North America, little is known about their early life history. We examined fecundity and early larval survivorship during sucker spawning events in three small Lake Michigan tributaries. Although egg deposition varied 25% among spawning events, estimated larval export to the lake varied over 25,000‐fold from around 1000 to 26 million. Based on variation in environmental conditions across years, it appears that spring flow and temperature may be important determinants of egg survival to larval outmigration. Larval age data suggest that most individuals that survived to outmigration hatched during a 2‐day period despite adult spawning across at least 10 days. Most larvae spent <2 weeks in the stream and emigrated around the time of transition from endogenous to exogenous feeding before substantial growth occurred. In two of three cases, larvae drifted exclusively at night; however, high drift rates occurred during both day and night in the case where larvae were very abundant, suggesting density‐dependent drift behaviour. Our results indicate that survival in tributary streams from egg deposition to larval export is highly variable in longnose suckers. These large differences in early life survival may translate into variability in recruitment, thereby influencing population structure and dynamics. 相似文献
11.
青蛤受精卵和幼虫密度对孵化和生长的影响 总被引：2，自引：1，他引：1
本文报道了青蛤受精卵密度对孵化的影响和青蛤幼虫培养密度对生长的影响。受精卵密度在26个/ml、30个/ml、38个/ml、44个/ml、53个/ml时,孵化率在87.8～89.9％之间;受精卵密度为53个/ml时,幼虫畸形率较高。实验发现,幼虫的培养密度应控制在6～11个/ml,幼虫变态后,减少培养密度,可以提高幼虫成活率。 相似文献
12.
We used a coupled physical–biological model to examine potential distances between hatching and settlement locations for lobsters in the Gulf of Maine. The physical model is based on a finite-element mesh and climatological averages of the seasonally evolving temperature and density fields. Larval trajectories from coastal and offshore hatching sites (21–224 m deep) were calculated for early, middle and late-season hatching by coupling temperature-dependent development rates and depth (the biological model) to the circulation. Model results showed large spatial differences in larval development times (from 18 to 38 days) and distances transported (19–280 km) for the early hatch. Development time and transport decreased markedly by mid-season at most sites, but strong spatial differences persisted. The eastern Maine coast appears to experience stronger removal and less resupply of larvae than other regions, consistent with observed lower recruitment. Inverse solutions of the model for larvae arriving in mid-coastal Maine indicate that they originate from a broad section of the eastern coast 'upstream', with those nearest the shoreline generally travelling the shortest distances. The postlarval stage is neustonic (living near the surface), and a simple inverse model demonstrates that a diurnal coastal sea breeze can contribute substantially to inshore movement during this final planktonic stage. Thus, offshore reproduction may be linked to inshore recruitment. 相似文献
13.
According to the match/mismatch hypothesis, larval fish survival and eventual recruitment is dependent on the offset time between the peaks of abundance of larvae and their planktonic prey. A rudimentary larval food supply model is developed to determine the dependence of food availability on the mismatch between peaks. The model predicts that recruitment variability should increase as spawning duration decreases, a result which is moderately supported by an analysis of Atlantic cod (Gadus morhua) data. 相似文献
14.
KEVIN M. BAILEY ANNETTE L. BROWN MARY M. YOKLAVICH KATHRYN L. MIER 《Fisheries Oceanography》1996,5(S1):137-147
Interannual variability in growth of larval walleye pollock Theragra chalcogramma was examined from 1983 to 1991 and of juveniles from 1985 to 1990. ANCOVA was used to assess differences in population growth rates, and an alternate method was developed to examine variations between annual length-at-age data and average 'expected' values over different age groupings. For larvae, the years 1986, 1987, 1989 and 1990 had higher than average length-at-age, and 1988 and 1991 had lower than average values. Relationships between growth and SST and larval density were not clear. A tentative relationship between copepod nauplii abundance and larval length-at-age was noted. The consequence of larval growth to larval mortality, late larval abundance or recruitment was not clear. We conclude that larval mortality rates are highly variable and tend to mask effects of moderate variability in growth on later abundance. For juveniles, 1987 had significantly lower than average length-at-age and 1988 had higher than average values. Although there are few years of data, they tend to support the importance of juvenile growth in the recruitment process. Conditions for the large 1988 year class are documented and discussed, including warm SST, calm winds, relatively low larval growth rates, low abundances of potential predators on larvae, low larval mortality rates, and high juvenile growth rates. 相似文献
15.
A series of experiments were conducted to evaluate the effects of diet, stocking density and environmental factors on the growth, survival and metamorphosis of short neck clam Paphia malabarica larvae. These experiments examined the following factors: diet [ Isochrysis galbana , Nannochloropsis salina and a mixture of I. galbana and N. salina (1:1 w/w)], stocking density (1, 3, 5 and 7 larvae mL−1 ), light intensity (unshaded, partially shaded and fully shaded) and water filtration (unfiltered and sand filtered). Results indicated that N. salina could replace 50% of I. galbana as a food source for the clam larvae with an increase in growth, survival (47.2%), metamorphosis (33.5%) and early settlement. Larval growth decreased significantly with increasing stocking density. A density of 1–3 larvae mL−1 appeared to be optimal for normal growth of clam larvae. Neither diet nor stocking density used in the study had a significant effect on larval survival. Under partially shaded (light intensity=1000–5000 lx) and fully shaded (light intensity <1000 lx) conditions, larval growth was significantly faster than under direct sunlight (unshaded). Larvae grew significantly faster in the unfiltered water than in the filtered water. 相似文献
16.
The distribution and movement between habitats with growth of the hard clam Meretrix lusoria were examined by comparing the size–frequency distributions among 17 sites in the Shirakawa–Midorikawa Estuary of the Ariake Sea. This clam is a commercially important bivalve in Japan, and its annual catch is largest in the Ariake Sea. At the study sites, new recruits were abundant at river mouths, and density was strongly affected by the distance from coastal tidal rivers and streams. In contrast, adults were widely distributed on tidal flats, although density was low at many sites. At marine site Oda, the density of adults was higher than that of new recruits at all sites and higher than that of juveniles at most sites. These results indicate that this species moves from riverine sites to marine sites with growth. Moreover, the observed low density of adult clams may indicate overfishing. The active movement of M. lusoria across the fishing grounds complicates the sustainable resource management of this species. Therefore, further studies are needed for effective resource management of M. lusoria. 相似文献
17.
Abstract— Predation on American shad ( Alosa sapidissima ) larvae within the first two hours of release was examined from 1989 to 1992 on 31 occasions at stocking sites in the Susquehanna River basin. Twenty-two fish species consumed shad larvae; the dominant predators were spotfin shiner ( Cyprinella spiloptera ), mimic shiner ( Notropis volucellus ) and juvenile smallmouth bass ( Micropterus dolomieu ). The number of shad larvae found in predator stomachs ranged from 0 to 900. Mortality of shad larvae at the stocking site was usually less than 2%. The greatest mortality (9.6%) occurred at the highest stocking level (1.5 million larvae). Highly variable predation rates and release levels of shad insufficient to achieve predator satiation hindered the ability to determine a specific type of functional response of predators. Predator numbers increased with stocking density, indicating short-term aggregation at the release site. Because of practical problems associated with releasing the large numbers of larvae that would be required to satiate predators, routine stocking at these levels is probably unreasonable. Releases of 400,000 to 700,000 larvae may reduce predation by offsetting depensatory mechanisms that operate on small releases and the effects of increased predation due to predator aggregation on large releases. Night stocking may reduce predation on larval shad at the release site. 相似文献
18.
Robert Klaus Bauer Daniel Stepputtis Ulf Gräwe Christopher Zimmermann Cornelius Hammer 《Fisheries Oceanography》2013,22(5):388-399
The investigation of larval dispersal and retention, their variability and dependence on wind conditions, has become a major topic in fisheries research owing to potential effects on stock recruitment and stock structuring. The present study quantifies the wind‐induced variability of larval retention of herring in a highly productive coastal lagoon of the Western Baltic Sea. This lagoon, the Greifswalder Bodden, represents the main spawning area of Western Baltic Spring‐Spawning Herring, a stock that has recently undergone a continuous decline in recruitment. The study tests whether this decline was related to changes in larval retention, more precisely to changes in wind conditions, the main forcing of the lagoon's circulation. To answer this, a model approach was applied. Larvae were tracked as Lagrangian drifters under constant and variable wind conditions, examining the main drift patterns and reconstructing the incidents during the period of recruitment decline. For the latter, weekly cohorts of virtual larvae were released in the lagoon over the entire spawning period (April–June; >16 weeks). The fraction of retained larvae per cohort was related to observed larval abundances. On this basis, a new retention index was defined to evaluate the annual larval retention. The results presented cannot explain the observed recruitment decline but characterize the lagoon as an important larval retention area by virtue of unsteady wind conditions that prevent a steady outflow of larvae. 相似文献
19.
Larval transport and retention of the spiny lobster, Panulirus argus, in the coastal zone of the Florida Keys, USA 总被引：1，自引：0，他引：1
The spiny lobster Panulirus argus is of ecological and commercial importance in the South Florida coast of the continental USA and throughout the Intra‐Americas Sea. Essential spiny lobster habitat in South Florida is primarily located in the Florida Keys coastal zone (including the Dry Tortugas), where the dynamic regional circulation coupled with the long planktonic larval duration (6–12 months) of P. argus raises questions of larval retention and recruitment. Locally spawned phyllosomata entrained in the Florida Current are likely to be expatriated out of the Straits of Florida, which implies that the local spiny lobster population is sustained by the transport of larval recruits from upstream locations. We examined the physical processes that may influence recruitment. Transport processes in the Keys coastal zone are spatially variable. Observed and modelled data suggest that the upper Keys is a point of onshore larval transport via the inshore meandering of the Florida Current, and the lower Keys to Dry Tortugas region apoint of retention through wind‐driven onshore/countercurrents and eddy recirculation. Eddies that propagate between the Dry Tortugas and the lower Keys facilitate the exchange of larvae between the Florida Current and the coastal zone. Northerly wind events associated with cold fronts can enhance recirculation of larvae in the upper Keys. The association of older larvae with the Florida Current front supports the hypothesis that spiny lobster larval recruits come from upstream sources in the Caribbean. 相似文献
20.
探讨低温(4 ℃)条件下的厚壳贻贝早期幼虫保存可能性,同时调查了不同培育密度对低温保存的影响。在正常条件下,继续培育低温保存后的幼虫,并调查其存活率和生长的变化。 结果表明,在低温保存后,早期幼虫存活率较高,超过95%;厚壳贻贝早期幼虫的壳长和壳高出现显著性的增长。不同培育组间,培育密度对厚壳贻贝早期幼虫的存活和生长影响不同,表明密度是幼虫低温保存的一个重要因素。在正常培育条件下,低温保存后的幼虫,3周后其存活率明显低于对照组,但仍超过50%,且其生长速度明显高于对照组。因此,低温培育是保存厚壳贻贝早期幼虫的有效方法,可用于今后贝类幼虫生物学实验和人工育苗技术的改善研究。 相似文献