共查询到20条相似文献,搜索用时 359 毫秒
1.
Larvae of jack mackerel Trachurus japonicus were sampled in seven depth layers (0–10 m, 10–20 m, 20–30 m, 30–40 m, 40–50 m, 50–70 m, and 70–100 m), with a closing-type
frame net, on 26th–27th February, 2003, at Sta. V (27°50′N, 126°00′E) continental shelf edge in the southern part of East
China Sea, to examine their vertical distribution. Most of the larvae (>90%) occurred in the upper 50 m layer during both
day and night. In the daytime, larvae of length from 3.0 mm to 4.5 mm were most abundant in the 10–20 m layer, those from
5.0 to 6.0 mm were most abundant in the 20–30 m layer, those from 6.0 to 8.0 mm occurred at greater depth, in the 30–40 m
layer, and those more than 9.0 mm were found in the 0–10 m layer and performed ontogenetic vertical migrations. Larvae from
6 mm to 8 mm length performed diurnal vertical migration, for the percentage (16.7%) of larval number in the 0–20 m layer
in the daytime increased to 42.1% at night and the percentage (78.1%) in the 20–50 m layer in the daytime decreased to 49.0%
at night. 相似文献
2.
Diana B. Reis Anastasia Shcherbakova Rodrigo Riera Virgina M. Martín Pedro Domingues Jos P. Andrade Pablo Jimnez‐Prada Covadonga Rodríguez Antnio V. Sykes Eduardo Almansa 《Aquaculture Research》2021,52(1):105-116
To move forward in the farming of Octopus vulgaris paralarvae, it is necessary to search for a live prey easy to obtain and maintain in the laboratory that meets the nutritional requirements of the octopus paralarvae and adapts to its predatory behaviour. Grapsus adscensionis zoeae (Crustacea, Decapoda) seems to fulfil most of these targets, and it was herein used to deepen knowledge of paralarvae lipid requirements and composition, growth and survival. To this purpose, the effects of feeding with Grapsus zoeae as sole prey were compared with Artemia at two different stages (nauplii and juveniles), which also differed in their lipid profiles. After 15 days of feeding, the best growth and survival of paralarvae was obtained in the Grapsus group, and no differences were observed between both Artemia groups. Triacylglycerides storage in paralarvae seemed to be co‐related with a lower growth and survival, but not with its prey levels. Contrarily, sterol ester levels were higher in paralarvae fed Grapsus, reflecting its content in the prey. The best paralarval viability was related to higher levels of 22:6n‐3 (DHA) and 20:4n‐6 (ARA), also reflecting its higher content in the prey. On the other hand, neither the 20:5n‐3 (EPA) levels in the prey nor in paralarvae were related to growth or survival. The implications of these results are discussed considering the lipid requirements of O. vulgaris paralarvae. 相似文献
3.
Takeshi Sakai Michio Yoneda Tetsuro Shiraishi Muneharu Tokimura Hiroshi Horikawa Michiya Matsuyama 《Fisheries Science》2009,75(4):895-902
We studied the age and growth of the lizardfish Saurida elongata using ground thin sections of otoliths (sagittae) from specimens collected in the Tsushima/Korea Strait between May 1999
and June 2001. A total of 695 individuals with fork lengths (FL) ranging from 189 to 478 mm were examined. The frequency of
translucent zone occurrence at the outer margin of the otoliths indicated that translucent zones formed once a year between
November and February. Most of the males examined were estimated to be 2–7 years old and the females, 3–9 years old. The maximum
estimated age of a male specimen was 10 years and that of a female, 11 years. The estimated von Bertalanffy growth curves
were FL
t
= 451{1 − exp[−0.172(t + 2.50)]} and FL
t
= 515{1 − exp[−0.151(t + 2.47)]} for males and females, respectively. At all ages, the FL at a specific age for females was greater than that for
males, suggesting that females of this species grow faster than males. 相似文献
4.
The functional response describes how consumption rate of individual predators changes as prey density changes, and can have important implications for the bottom culture of scallops. We examined (i) the functional response of rock crabs (Cancer irroratus) preying on juvenile sea scallops (Placopecten magellanicus); (ii) the effect of substrate type and scallop size on the functional response; and (iii) the underlying behavioural mechanisms of observed functional responses. Specifically, we quantified predation rate and behaviours, such as the proportion of time spent searching for prey, encounter rate between predators and prey and the outcomes of encounters, when individual rock crabs were offered a range of scallop density (2–50 or 11–111 scallops m−2) and two size classes of scallops (∼
∼25 and ∼
∼35 mm shell height) on two different substrate types (“glass-bottom” and “granule”). We found that crab predation rate on small juvenile scallops increased at a decelerating rate with prey density to a plateau at high prey density on both substrates, indicating a hyperbolic (type II) functional response. Crab predation rate on large juvenile scallops was independent of prey density (i.e., no functional response evident), suggesting that crabs were at their satiation level. Prey density did not influence any behaviour except encounter rate on small juvenile scallops, which increased as prey density increased. Substrate type influenced crab predation: maximum predation rate of crabs on small juvenile scallops and encounter rate with either size of juvenile scallops was lower on granule than on glass-bottom. Our results in the laboratory suggest that crabs could potentially be swamped if scallops are seeded at a high density in the field. However, many factors in the field may influence the functional response. For example, the presence of multiple prey types may lead to sigmoid functional responses, while the presence of many crab individuals may lead to aggregation of crabs in areas of high prey density. 相似文献
5.
Life strategies of cephalopod paralarvae in a coastal upwelling system (NW Iberian Peninsula): insights from zooplankton community and spatio‐temporal analyses 下载免费PDF全文
Álvaro Roura X. Antón Álvarez‐Salgado Ángel F. González María Gregori Gabriel Rosón Jaime Otero Ángel Guerra 《Fisheries Oceanography》2016,25(3):241-258
The early life stages of cephalopods ‐ octopods, squids, sepiolids and ommastrephids ‐, are uncommon in zooplankton samples and little is known about their life strategies. Accordingly, cephalopod paralarvae were examined in the upwelling ecosystem of the Ría de Vigo (NW Spain) at night from 2008 to 2010. Multivariate analyses and generalized linear models (GLMs) were used to explore relationships between cephalopod paralarvae and the zooplankton communities that they inhabited in 2008. In addition, the foraging strategy and prey preferences of Octopus vulgaris paralarvae within these communities were determined. Multivariate and GLM results showed a strong association of cephalopod paralarvae with coastal and frontal zooplankton communities. Octopus paralarvae were shown to be specialist predators with a strong preference for decapod zoeae in each of the communities examined. Using the three years of sampling, GLM analyses of paralarval spatio‐temporal variations in relation with the upwelling strength showed a positive relationship with upwelling intensity for O. vulgaris and sepiolids, as well as contrasting temporal, horizontal and vertical distributions for the different paralarvae analysed. Under strong upwelling events, Octopus paralarvae were more abundant in surface waters, whereas the abundance of loliginids and sepiolids was higher in the water column. This vertical behaviour in conjunction with the physical conditions of the Western Iberian Upwelling ecosystem suggests the coexistence of two different life strategies: a coastal strategy displayed by loliginid and sepiolid paralarvae that are retained over the shelf, and an oceanic strategy displayed by O. vulgaris paralarvae that are dispersed far from the shelf. 相似文献
6.
The diet of juvenile (predominantly age 1) southern bluefin tuna Thunnus maccoyii (SBT, N = 720), caught over 11 years of the recruitment monitoring survey off southern Western Australia during summer, consisted
overwhelmingly of teleosts (97.4% by volume). Pilchard Sardinops sagax (27.4%V), blue mackerel Scomber australasicus (16.7%V), and jack mackerel Trachurus declivis (14.2%V) were the major taxa, with pilchard more abundant in coastal waters and jack mackerel more frequently encountered in fish
caught closer to the shelf-edge. Prey size varied from 5 to 240 mm, with 67% of ingested items measuring between 30 and 50 mm.
Pilchard dominated the prey size category 130–190 mm (84% by number), but the overall contribution of this species to the
diet of juvenile SBT was much lower than previously reported. Future research in relation to the feeding ecology of juvenile
SBT should focus on the biology and ecology of the young lifestages of the main prey species in this area and on prey distribution
and dynamics as a key factor linking environmental change and SBT distribution. 相似文献
7.
The potential for predation by the sea stars Asterias rubens and Marthasterias glacialis on seed-size (41 ± 3 mm shell height) juvenile scallops (Pecten maximus), ready for seeding in sea ranching areas, was investigated in a 30-day laboratory predation experiment. There was no significant
difference (P > 0.05) in predation rate of large A. rubens (95–115 mm radium) and large M. glacialis (120–164 mm radius), which averaged 0.88 and 0.71 scallops individual−1 day−1, respectively. Maximum rates of predation were 2.44 scallops individual−1 day−1 for large A. rubens and 3.00 scallops individual−1 day−1 for large M. glacialis. Small M. glacialis (76–87 mm radius) had a significantly lower predation rate than large individuals of either species (average 0.13 scallops
individual−1 day−1, P < 0.05). Small A. rubens (50–80 mm radius) only began to prey on scallops when average scallop size was reduced to 35 mm. Based on estimated density
of sea stars at a Norwegian sea ranching site and average predation rates, a population of scallops seeded at 10 m−2 would be reduced by between 0.5 and 11% in 1 month. Furthermore, using the highest observed predation rate, the degree of
loss of scallops indicated that scallop culture via sea ranching would not be economically viable and thus methods for reducing
scallop predation by sea stars are necessary. 相似文献
8.
Toshihiro Wada Kyoichi Kamiyama Shinya Shimamura Ikuo Matsumoto Takuji Mizuno Yoshiharu Nemoto 《Fisheries Science》2011,77(5):785-793
Habitat utilization, feeding, and growth of a rare pleuronectid flatfish, spotted halibut Verasper variegatus, were examined in a brackish lagoon in northeastern Japan: Matsukawa-ura. The distribution and date–length data of spotted
halibut collected mainly from beam-trawl samplings during 1983–2008 indicated that age-0 juveniles [n = 25, 6.0–18.0 cm total length (TL)] and older spotted halibut (n = 71, 13.8–43.0 cm TL) inhabited almost the entire northern part of Matsukawa-ura. Comparative distribution surveys of spotted
halibut, stone flounder, and marbled flounder during 1985–1989 revealed similar distribution patterns of these flatfishes;
the highest densities were found around the central part of Matsukawa-ura, although significantly lower abundance was detected
for spotted halibut. Linear growth equations of age-0 juveniles demonstrated that spotted halibut were able to achieve high
growth after June, probably because abundant prey (e.g., mysids and gammarids) and suitable physical conditions (warmer water
temperature and lower salinity) were present. The main prey items shifted from various crustaceans including mysids, caridean
shrimps, and anomurans to brachyura Hemigrapsus spp. (≥20 cm TL). Our study shows that spotted halibut use the shallow brackish lagoon as an important nursery for juveniles,
and also as a feeding ground for young and adults. 相似文献
9.
Youji Wang Menghong Hu Weimin Wang Ling Cao Yi Yang Biping Lü Rongrong Yao 《Aquaculture International》2008,16(6):539-549
The diel feeding rhythm and ontogenesis during early life stage of loach Misgurnus anguillicaudatus were investigated under experimental conditions (light: L 06:00–18:00, D 18:00–06:00 h). Morphological and behavioral developments
of loach from newly hatched to 40 days after hatching were observed. Larvae were able to prey on daphnia 3–4 days after hatching
at 23 ± 0.5°C. As the larvae grew, they showed an increasing feeding capacity and a distinct feeding rhythm. Feeding intensity
and incidence for day-4 larvae were highest at 10:00 and 16:00 h. The highest levels of feeding intensity for day-12 larvae
occurred at 08:00, 12:00, and 18:00 h as did feeding incidence. By day 20, when the larvae metamorphosed, the highest levels
of feeding intensity occurred at 06:00, 18:00, and 24:00 h and were concurrent with the highest feeding incidence. After metamorphosis,
feeding capacity had again increased considerably and, in contrast to the earlier stages before day 20, feeding intensity
for day-30 juveniles peaked at 05:00 and 20:00 h, about 1–2 h after the maximum feeding incidence. The feeding rhythm of loach
juveniles at day 40 was almost the same as the day-30 juveniles. The estimated maximum daily feeding rates were 43.1%, 33.4%,
19.0%, 12.8%, and 5.8% of body weight on days 4, 12, 20, 30, and 40, respectively. Thus, loach was found to have different
feeding rhythms in the pre- and post-metamorphosis stages, with the highest feeding activity in daytime during the larval
planktonic stage before metamorphosis, and intensely nocturnal feeding behavior during the juvenile benthic stage after metamorphosis. 相似文献
10.
Shiro Itoi Junpei Odaka Shunsuke Noguchi Tsutomu Noda Kohei Yuasa Toshihiko Muraki Taichi Tanabe Noriyuki Takai Kiyoshi Yoshihara Haruo Sugita 《Fisheries Science》2011,77(6):975-981
Scombrops gilberti is a member of the percoid family Scombropidae, which includes a single genus and three to four species worldwide. Little
is known about the ecology of this species. Juvenile S. gilberti have been found in the waters off northern Japan (Iwate Prefecture), whereas adults are found in the waters around the southern
counterpart (Izu Islands), approximately 700 km from the northern waters. In the present study, we captured immature S. gilberti (106–248 mm standard length, SL) in the northern waters by set net at 8–80 m depth, whereas larger individuals (150–328 mm
SL) were captured by trawling at 150–500 m depth. By contrast, only adult S. gilberti (422–590 mm SL) were captured in the southern waters. The genetic composition of the adult population of S. gilberti from the southern waters and of the juvenile population from the northern waters was compared using the nucleotide sequence
of the mitochondrial DNA (mtDNA) cytochrome b gene. No significant differences in genetic parameters such as fixation index, neutrality test or mismatch distribution analysis
were found between these geographically distinct populations of S. gilberti, showing that these populations are genetically homogeneous. 相似文献
11.
Effect of starvation on the performance of baby octopus (Robsonella fontaniana) paralarvae 下载免费PDF全文
Ana Farías 《Aquaculture Research》2017,48(11):5650-5658
The aim of this study was to evaluate the effect of short‐ and long‐term starvation on paralarvae from hatching and compare to fed paralarvae. In the continuous starvation treatments, paralarvae at hatching were left without food as independent treatments for 5, 8, 9, 10, 11, 12, 13 and 15 days. In the fed treatments, the newly hatched paralarvae were fed for five and eight days; then each group was left in starvation as independent treatments for 3, 5 and 7 days. After any experimental starvation period, the paralarvae were fed for five more days to evaluate their recovery. Paralarvae exposed to continuous starvation from hatching endured up to 8 days after hatching (8 SDAH) showing significant recovery. Its survival decreased proportionally to the days of starvation, without any recovery after 12 DAH. Fed paralarvae (5 and 8 FDAH), resulted in significant differences accordingly to the length of the starvation period. Paralarvae left under permanent starvation showed a noticeable decrease in their arm/mantle length ratio and an atrophy of the digestive gland was observed. Amino acids were used primarily as energy source by paralarvae, particularly in the second week of starvation. It is discussed the critical age to avoid deleterious effects of starvation on paralarvae. 相似文献
12.
Stable isotopes and gut contents indicate differential resource use by coexisting asp (Leuciscus aspius) and pikeperch (Sander lucioperca) 下载免费PDF全文
Mojmír Vašek Antti P. Eloranta Ivana Vejříková Petr Blabolil Milan Říha Tomáš Jůza Marek Šmejkal Josef Matěna Jan Kubečka Jiří Peterka 《Ecology of Freshwater Fish》2018,27(4):1054-1065
Differential use of habitat and prey resources is an important mechanism that may allow coexistence of sympatric species. Unlike interactions between smaller cyprinid and percid fishes, the resource use by coexisting predatory asp (Leuciscus aspius) and pikeperch (Sander lucioperca) is relatively unknown. Here, gut content and stable isotope analyses were used to study ontogenetic dietary shifts and interspecific trophic niche overlap between asp and pikeperch coexisting in two reservoirs. The hypothesis that both species show an ontogenetic dietary shift from small invertebrates to large fish prey, but at the same time use different prey resources to reduce potential competitive interactions, was validated. The isotopic niches of the two predators showed no, or only a moderate, degree of overlap (0%–65%). The ontogenetic changes in the degree of interspecific isotopic niche overlap were different in the two reservoirs, suggesting that trophic segregation can be dynamic and variable among systems. Gut contents revealed that small (<100 mm standard length) asp consumed mostly terrestrial invertebrates and emerged aquatic insects, whereas small pikeperch foraged on zooplankton, larval and pupal stages of aquatic insects and fish. Larger individuals (>100 mm) of both species were predominantly piscivorous, with asp consuming more cyprinid prey and pikeperch more percid prey. Coexisting asp and pikeperch populations are able to utilise different prey resources, thereby reducing potential negative competitive interactions. 相似文献
13.
József Lanszki Zsuzsanna S. Pallos Dénes Nagy Grace Yoxon 《Aquaculture International》2007,15(5):393-402
The diet composition and fish preference of piscivorous Eurasian otters (Lutra lutra) were studied in two fish farm systems in Hungary using spraint (otter faeces) analysis during two wintering periods. The
primary food source of otters in both fish farms was fish (97–99% of biomass). The main fish prey was small-sized, below 100 g
in weight (96% in both areas), while fish prey above 500 g comprised only 0.1–0.4% of the diet. The bulk of the otters’ diet
consisted of less-valued species, especially non-native Prussian carp (Carassius auratus gibelio). Consumption of commercial fish species ranged between 15 and 31% of the total diet. Otters preferred fish below 100 g in
weight (Ivlev’s electivity index, E
i
= 0.65–0.70), and showed a lesser preference for (or avoided) fish above 100 g in weight (E
i
= −0.37–1.00). With regard to species distribution, otters preferred small (below 100 g) grass carp (Ctenopharyngodon idella), zander (Sander lucioperca), pike (Esox lucius), Prussian carp, topmouth gudgeon (Pseudorasbora parva), while they consumed common carp (Cyprinus carpio), the most important commercial species, proportionally to its abundance in the environment (E
i
= −0.18–0.29). 相似文献
14.
Satoshi Watanabe Satoshi Katayama Masashi Kodama Naritoshi Cho Kaoru Nakata Masaaki Fukuda 《Fisheries Science》2009,75(4):937-945
The relative contribution of particulate organic matters (POMs) in water column and sediment as a food source for the Manila
clam, Ruditapes philippinarum, was studied using carbon and nitrogen stable isotopic method (δ13C and δ15N) in a tidal flat at Seaside Park, Yokohama, Japan. Comparisons of δ13C and δ15N among R. philippinarum and POMs in surface water, bottom water, and sediment surface indicated that R. philippinarum larger than 5 mm shell length (SL) mainly assimilated benthic POM, and individuals smaller than 5 mm SL assimilated benthic
and pelagic POM. Continuous measurements of chlorophyll concentrations in the bottom water revealed tide-driven resuspension
of the benthic phytopigments. R. philippinarum showed differences in δ13C and δ15N along an inshore–offshore transect, indicating small-scale spatial differences in POM provision in the tidal flat. These
findings suggest that POM in the bottom water, supposedly inhaled by R. philippinarum, is a mixture of a larger proportion of resuspended benthic POM and a smaller proportion of pelagic POM, and that the mixing
ratio of the POMs may be affected by the hydrodynamics of flooding water associated with tidal flat topography. 相似文献
15.
Tatsuya Kawakami Hiroyuki Okouchi Masato Aritaki Jun Aoyama Katsumi Tsukamoto 《Fisheries Science》2011,77(2):183-190
The embryonic development and morphology of eggs and newly hatched larvae of the Pacific herring Clupea pallasii were described using laboratory-reared specimens originating from the Miyako Bay stock. The eggs were almost spherical in
shape, 1.33–1.46 mm (mean: 1.38 mm) in diameter, and had a thick adherent chorion. They had a segmented pale yellow yolk,
no oil globule, and a relatively wide perivitelline space. A subgerminal cavity was observed during the gastrula period, whereas
the blastocoel did not appear. Mass hatching occurred by 271 h 45 min after fertilization, and the newly hatched larvae were
7.1–7.7 mm (mean: 7.5 mm) in total length with 53–56 myomeres at 9.6°C. The embryonic development of Pacific herring was substantially
similar to that of zebrafish Danio rerio, American shad Alosa sapidissima, as well as Atlantic herring Clupea harengus, and generally followed the basic developmental pattern of teleosts. However, Pacific herring larvae hatched at a more developed
stage than some other clupeoids, such as Japanese sardine Sardinops melanostictus, and the progressed developmental stage at hatching could be interpreted as an advanced adaptation. 相似文献
16.
Paloma Feyjoo Rodrigo Riera Beatriz C. Felipe Alí Skalli Eduardo Almansa 《Aquaculture International》2011,19(1):193-204
Ammonia and nitrite are among the most important water quality parameters. The aim of this study was to determine the acute
toxicity of unionized ammonia and nitrite on newly hatched Octopus vulgaris paralarvae. Concretely, survival, feeding and chromatophore activity were examined under different NH3 and NO2
− concentrations. The median lethal concentration (LC 50) determined for 24 h was 10.7 ppm for NH3 and 19.9 ppm for NO2
−. Based on these results, a concentration range was chosen to test the effect of this environmental contaminants in feeding
and chromatophore activity (range between 2.5 and 20 ppm for feeding and 10 and 30 ppm for chromatophore activity), resulting
in modifications in both parameters. In fact, a significant decrease (P < 0.05) in Artemia nauplii consumption by the paralarvae was observed with an increase in NH3 and NO2
−. Similarly, the chromatophore activity was also affected by concentration of these contaminants, with decreasing response
(P < 0.05) when submitted to stressful situations, as the ammonia and nitrite concentration was increased. 相似文献
17.
D.B. Reis I. García‐Herrero R. Riera B.C. Felipe C. Rodríguez A.V. Sykes M.V. Martín J.P. Andrade E. Almansa 《Aquaculture Nutrition》2015,21(6):797-806
In this study, two new alternative preys: Grapsus adscensionis zoeae (as sole prey) and Palaemon elegans zoeae (in cofeeding with Artemia sp.), as well as, Artemia sp. juveniles were used as feed for octopus paralarvae, as a way to understand its lipid requirements. Total lipid (TL) content, lipid class (LC) and fatty acid (FA) profiles of preys, octopus hatchlings and 9‐day‐old paralarvae were analysed. Growth and survival of the paralarvae were also determined. Regardless the prey provided, a notable shift in the lipid profile of paralarvae was registered after 9 days of rearing. The highest index of growth rate (IGR) recorded when decapod crustacean zoeae were supplied might have some relation with levels of 20:4n‐6 (ARA) and DHA/EPA ratio observed. In this sense, Grapsus adscensionis zoeae leaded to a higher content of ARA and a lower content of EPA, which may indicate a possible competition between these two FA. For that a balanced EPA/ARA ratio might be significant in this species nutrition without disconsidering DHA levels as an essential fatty acid. Finally, the changes observed in paralarvae FA profile might not only be related to prey FA profile, but also with changes occurring in the lipid classes contents. 相似文献
18.
Marcelino Herrera Ismael Hachero-Cruzado Catarina Oliveira José F. Ferrer José M. Márquez Montserrat Rosano Jose I. Navas 《Aquaculture International》2010,18(3):475-485
The weaning phase can be decisive in fish-culture viability. In this work, the relationship between the initial size and weaning
success has been studied in wedge sole (Dicologoglossa cuneata). For each age (30, 50, and 70 days after hatching, DAH), two to three sizes were selected, and all were put on the same
feeding schedule for 20 days. Each batch (three replicates) was sampled at 1, 10, and 20 days. Specific growth rate (SGR)
and survival were compared at the end of the co-feeding period, after 10 days on dry feed only. The best results for survival
and growth were found with the smallest larvae, and vice versa. The SGRs and survival rates recorded during the co-feeding
period were higher (0.8–15.6 day−1 and 68.3–97.8%) than those from the dry-food phase (0.9–4.7 day−1 and 56.3–66.7%). Successful weaning (survival = 65% and SGR = 9.3 day−1) is possible with 30 DAH larvae (7.6–8.1 mm and 3.9–4.6 mg). In conclusion, the most effective weaning would be possible
at 30 DAH, implying significant Artemia savings (25–50%). 相似文献
19.
Muzaffer Mustafa Harlıoğlu 《Aquaculture International》2009,17(1):31-43
Growth experiments carried out with two juvenile crayfish species, Astacus leptodactylus Eschscholtz and Pacifastacus leniusculus (Dana), at different temperatures and densities highlighted the problem of cannibalism under conditions aimed at intensifying
crayfish production. Cannibalism proved to be much lower in A. leptodactylus than P. leniusculus, suggesting that the former might be the better candidate for astaciculture. In the first of two population survival trials,
A. leptodactylus showed a higher survival rate than P. leniusculus, with 26% of P. leniusculus surviving in the first replicate, compared to 42.3% of P. leniusculus, and 40.76% surviving in the second replicate, compared to 47.6% of P. leniusculus. The same trend was observed in the second experiment, with P. leniusculus showing survival rates of 48.5 and 55.3% (first and second replicates, respectively) in comparison to 65.2 and 68.2%, respectively,
for A. leptodactylus. It is therefore highly likely that if P. leniusculus were to become established in Turkey, it would outcompete the native A. leptodactylus even if it were not to be devastated by the crayfish plague that has decimated the native species. The experiments also highlighted
the problem of differential growth, with some juveniles hardly growing at all while others reached a relatively large size.
The range in carapace length (CL) was 9–18 mm for A. leptodactylus and 8.5–18.5 mm CL for P. leniusculus at the end of the first experiment. While both species grew quickly, P. leniusculus hatched earlier, giving it an advantage over A. leptodactylus; consequently, by the end of the summer, the juveniles of the former were larger than those of A. leptodactylus. Specific growth rate values showed that the juveniles of the two species had similar growth rates. The results also revealed
that growth was not significantly affected by density in both species at 15°C, but at 25°C, growth was significantly better
at a density of 234 juveniles m−2 than at 468 juveniles m−2, and better at 468 juveniles m−2 than at 937 juveniles m−2 (P < 0.01 and P < 0.001, respectively). We conclude that P. leniusculus is a good candidate for aquaculture as it has a rapid growth rate and early hatching and maturity; however, its aggressive
behavior may make it a less attractive proposition than A. leptodactylus, which is also fast growing but less aggressive.
This study is a part of PhD study of M.M. Harlıoğlu, who is supported by Fırat University Elazığ, Turkey. 相似文献
20.
We monitored feeding behavior and survival of starved juvenile olive flounder experimentally infected with the gill monogenean
Neoheterobothrium hirame. Infected flounder increased amount of the time spent in the water column by 117% when trying to capture live mysids, Neomysis sp. They also showed different feeding patterns from those of uninfected fish and made fewer attacks towards prey during
one feeding attempt. Although the average numbers of mysids captured by individuals were similar between infected and uninfected
fish, heavily infected fish tended to catch less prey. These results indicate that N. hirame reduces the feeding efficiency of the host for capturing live prey and possibly makes them more vulnerable to predation during
feeding. We could not detect any obvious difference in survival rates between uninfected, lightly and heavily infected fish
during 3 months of starvation. There was no evidence that starvation makes fish more susceptible to N. hirame. The present study provides first experimental evidence that N. hirame affects feeding behavior of juvenile olive flounder and supports the idea that this parasite indirectly reducing the host’s
survival and may be responsible for the recent reduction of the flounder population in Japan. 相似文献