Swimbladder inflation,growth and survival of yellowtail kingfish Seriola lalandi (Valenciennes, 1833) larvae under different temperature,light and oxygen conditions

Poor swimbladder inflation leads to low fish survival due to resulting spinal deformities and the inability to feed and develop normally. Failure of swimbladder inflation may be attributed to the inappropriate range of abiotic conditions. This study investigated the effects of temperature, light source and intensity, and oxygen conditions on initial swimbladder inflation, growth and survival of yellowtail kingfish Seriola lalandi larvae. The study consisted of four separate trials including low (21.5°C) and high (24.5°C) temperatures, natural and artificial light sources, low (1000 lux) and high (32 000 lux) light intensities, and ambient and supersaturated dissolved oxygen. Initial swimbladder inflation was only significantly affected by light source, with the highest inflation rate (97.5 ± 3.5%) under artificial light. Fish growth was improved at the higher temperature and at the higher light intensity. Survival was only significantly influenced by light intensity, with the highest survival (11.0 ± 2.3%) at the high intensity (32 000 lux). This study indicates that light source affects swimbladder inflation timing and high artificial light intensity improves larval fish growth and survival.     

The effect of light intensity on development and hatching success of lingcod, Ophiodon elongatus (Girard), eggs

The influence of incubation light intensity on development and hatching success of the lingcod (Ophiodon elongatus Girard) was studied by determining time to hatch, per cent hatch (total and viable) and per cent of deformities for embryos incubated at three different light intensities: ～0, 1, and 563 lux. Photoperiod for the last two treatments was 16 h dark: 8 h light. Chemical parameters throughout incubation remained within acceptable ranges. Hatching in all treatments began 43 days post fertilization (353 °C days) and was complete on day 46 (377 °C days), with peak hatch for all treatments on day 44 (361 °C days). Per cent viable hatch for eggs incubated in the 1 lux treatment (88.6 ± 2.1%; mean ± SEM) was significantly greater than eggs incubated in the ～0 lux (59.6 ± 11.3%) and 563 lux (61.4 ± 9.2%) treatments. A significantly greater per cent of deformed embryos with curled bodies occurred at 563 lux (9.5 ± 2.6%) compared with the 1‐lux treatment (2.5 ± 0.6%). No significant differences for the other categories of deformities (ball, short, distended gut) were detected among treatments. Total deformities (all categories combined) for ～0 lux (16.0 ± 4.2%) and 563 lux (17.2 ± 3.3%) were significantly greater than total deformities for 1 lux (5.0 ± 1.4%).     

底质类型对中国明对虾存活、生长及行为特征的影响

在实验室内营造半精养、精养养殖模式,研究不同养殖模式下底质类型(未添加底质、水泥底、全沙底、沙泥底和砂砾底)对中国明对虾(Fenneropenaeus chinensis)存活、生长及行为特征的影响.结果表明,半精养模式下,中国明对虾的存活率和蜕皮频率在各底质处理组间均无显著差异(P＞0.05);而精养模式中未添加底质处理组实验虾的存活率和蜕皮频率最低,沙泥底处理组存活率和蜕皮频率最高,分别达到100％和12.9％/d.两种养殖模式下,底质类型对中国明对虾的特定生长率(SGR)均有显著影响(p＜0.05),其中半精养模式沙泥底处理组实验虾的SGR最高,是未添加底质处理组的1.39倍;而精养模式未添加底质处理组的SGR最高,达到1.94％/d,但其与全沙底和沙泥底处理组无显著差异(P＞0.05).底质类型对实验虾的行为特征亦有显著影响(P＜0.05),半精养模式沙泥底处理组实验虾的寻(摄)食虾比率和运动率在投喂饵料前后均最高,而攻击频率在投喂饵料前于全沙底处理组中最高,投喂饵料后则在未添加底质处理组中最高,达到4.5次/(ind.h),但其与沙泥底和砂砾底处理组无显著差异(P＞0.05);精养模式下,投喂饵料前全沙底处理组实验虾的寻食虾比率和攻击频率最高,而运动率在各处理组之间无显著差异(P＞0.05),投喂饵料后实验虾的摄食虾比率在未添加底质处理组中最高,而在砂砾底处理组中最低,运动率和攻击频率则在沙泥底处理组中最高.综合分析表明,底质的添加有利于提高中国明对虾的生长和存活,且底质添加后实验虾能够根据不同底质环境进行行为的调节与整合.在本研究的4种底质类型中,中国明对虾更偏好于泥含量为30％的沙泥底质.     

Effect of light intensity and photoperiod on Nile tilapia Oreochromis niloticus L. seed production

The objective of this study was to compare the effect of six light intensity/photoperiod combinations (2500 lux/18 h, 2500 lux/15 h, 2500 lux/12 h, 500 lux/18 h, 500 lux/15 h and 500 lux/12 h) on seed production in the Nile tilapia Oreochromis niloticus L. Each combination represented a treatment and was triplicated in 0.4‐m³ fibreglass tanks within a recirculating water system. Water temperature was maintained at 29.0 ± 1.0 °C. Males and females with mean body weights of 116.8 and 91.6 g, respectively, were stocked at a rate of eight fish/tank with a male to female ratio of 1:3. Seeds (eggs, sac fry and swim‐up fry) were collected every 2 weeks. The experiment lasted for a total of 120 days. The results showed that the 2500 lux/18 h treatment produced significantly greater (P < 0.05) total seed/tank (4944), seed kg^?1 female day^?1 (50.9), seed m^?2 day^?1 (40.3) and seed/ female day^?1 (6.7) than treatments with medium or short photoperiods (15 and 12 h day^?1 respectively) or lower light intensity (500 lux). The degree of spawning synchrony and percentage of the sac and swim‐up fry stages were significantly higher in the 2500 lux/18 h treatment than in the other treatments. Under the conditions tested in this study, seed production and spawning synchrony in the Nile tilapia may be improved by subjecting breeders to a light intensity of 2500 lux and a photoperiod of 18 h day^?1.     

The Effects of light intensity on growth and survival of cuttlefish (sepia officinalis) hatchlings and Juveniles

The effects of three light intensities (100, 350 and 1200 lux) on cuttlefish hatchling rearing performance was studied in black tanks. A total of 270 cuttlefish with a mean wet weight (MWW) of 0.089 ± 0.012 g were used in the experiment, which was undertaken during the first 50 days after hatching (hatchling stage plus the transition to the juvenile stage). According to results of the present study, light intensity is an important factor for growth and survival consistency in cuttlefish rearing. All three light intensity groups displayed exponential growth. The effect of days, light intensity and their interaction only displayed differences (P < 0.05) between light groups in terms of mean wet weight. The 100 lux light intensity promoted the best absolute values of total biomass and total mortality. We believe that the higher mortality observed in 1200 lux reared cuttlefish during the first 10 days after hatching (DAH) was due to light intensity and individual adaptation to light conditions. Therefore, the 100 lux light intensity, obtained with daylight spectrum bulbs, is recommended for cuttlefish rearing during the first 50 DAH. This light setup promotes higher growth and survival rates and lower energetic costs, which are key aspects to consider in a cuttlefish hatchery.     

Maturation and spawning performance of pond-reared Penaeus merguiensis in different combinations of temperature, light intensity and photoperiod

The combined effects of temperature (23 and 27 °C), light intensity (1100 and 2 lux or ≈ 21.5 and 0.04 μEinst m^?2 s respectively) and photoperiod (10 h light/14 h dark and 14 h light/10 h dark) on ovarian maturation and spawning performance of ablated pond‐reared Penaeus merguiensis were investigated in a 51‐day experiment. The results showed that temperature was the most influential factor, followed by light intensity, whereas the effect of photoperiod was minor. As the maturation process progressed, the effects of temperature and light intensity became stronger while that of photoperiod became less significant. Temperature significantly affected all the reproductive parameters assessed. Prawns in the 27 °C treatments outperformed those in the 23 °C treatments (P < 0.05). The effect of light intensity was found to have a significant effect (P < 0.05) only on the proportion of spawners (prawns that spawned) and spawning rate. More prawns spawned at a higher rate under dim light (2 lux) than under strong light (1100 lux). Photoperiod affected only the proportion of prawns reaching stage III of ovarian development (P < 0.05). There were interactions between temperature and light intensity affecting the proportion of prawns reaching stage III and, although not significantly, the proportion of spawners (P = 0.177), fecundity (P = 0.134) and survival (P = 0.061). Overall, it is recommended that a combination of 27 °C, 2 lux and 10 h light/14 h dark is suitable for the maturation of pond‐reared P. merguiensis. There were indications that temperature can be used to control the rate of ovarian maturation. Also, it is possible to increase light intensity up to 1100 lux in P. merguiensis hatcheries if prawns are ablated.     

Low light inhibits native fish movement through a vertical‐slot fishway: Implications for engineering design

Light intensity within a vertical‐slot fishway was manipulated to determine the effect on fish movement. Three treatments (darkness, low light, artificial light) were tested with natural daylight used as a control. Light intensity varied from 0 to 1,692 lux for the three treatments and from 1 to 4,550 lux for the control. Light intensity outside the fishway ranged from 31 to 80 900 lux. A total of 64 385 fish were collected from six species. The abundance of Australian smelt Retropinna semoni (Webber), unspecked hardyhead Craterocephalus stercusmuscarum fulvus Ivantsoff, Crowley and Allen, bony herring Nematalosa erebi (Günther), carp gudgeon Hypseleotris spp. and Eastern gambusia Gambusia holbrooki (Girard) moving upstream reduced significantly under low‐light conditions. Conversely, movement of macroinvertebrates (freshwater shrimp Macrobrachium australiense Holthuis and freshwater prawn Paratya australiensis Kemp) increased at low‐light intensities. The number of fish moving under artificial light (28 617) was similar to that under natural daylight (33 919). Movements of Australian freshwater fish and macroinvertebrates were found to be influenced by changes in light intensity. Instream structures that alter light conditions, such as road culverts, may thus act as behavioural barriers to fish movement, and this could be mitigated by the provision of natural or artificial light.     

Effects of mud substrate and water current on the behavioral characteristics and growth of the sea cucumber Apostichopus japonicus in the Yuehu lagoon of northern China

To determine whether marine mud substrate is suitable for sea cucumber aquaculture, we studied the effects of sea mud on the behavioral characteristics, growth and survival of Apostichopus japonicus, in both the field and laboratory. Our results showed that sea mud is beneficial for the growth of A. japonicus, but was unfavorable for its locomotion and attachment when a water current was present. In the field experiment in Yuehu lagoon, juvenile A. japonicus preferred to inhabit the base of seaweeds or dead leaves, which provide a favorable substrate for both their locomotion and ingestion. The mud substrate was not suitable for the small juveniles to inhabit; therefore, >3.25 g ind^?1 is the preferred size for bottom-sowing culture of sea cucumbers on the seabed in a field environment such as the Yuehu lagoon. Water current is a key factor influencing sea cucumber distribution on the bare mud substrate, with 90 % of juvenile sea cucumbers (<40 g ind^?1) being unable to keep still in a current speed of 0.115 m s^?1 for 10 min. In conclusion, a mud substrate is suitable for A. japonicus aquaculture, although hard substrates or shelters are a prerequisite for successful rearing. The water current is a key factor that influences substrate selection by A. japonicus and, thus, is an important factor to be considered in the bottom-sowing culture of these organisms.     

The effects of different daytime light intensities on the diel patterns of plasma melatonin in fingerling and broodstock rainbow trout (Oncorhynchus mykiss)

Diel plasma melatonin levels were measured to determine the effects of varied light intensities in juvenile and adult rainbow trout. This study showed that night-time melatonin plasma concentrations were significantly higher (P?<?0.05) in juveniles (600±75 pg/mL to 492±29 pg/mL) than broodstock (314±3 pg/mL to 265±55 pg/mL) at 1250 lux. Light intensities of 700 lux were unresponsive in both groups. This amplitudinal difference between juvenile and adult fishes response to light may suggest a developmental importance of melatonin.     

Galanin and β-endorphin as feeding regulators in cyprinids: effect of temperature

The effects of intracerebroventricular (ICV) and intraperitoneal (IP) administration of galanin and β-endorphin on food intake have been studied in satiated tench held at 21 ± 2 °C. Food intake was evaluated at 0–2 h and 2–8 h after injection. The same treatments were carried out in tench and goldfish acclimated to 10 ± 1 °C. Central administration of either galanin or β-endorphin significantly increased food intake at 2 h and 8 h after injection in tench acclimated to 21 ± 2 °C, but no change in feeding was observed after IP treatments. Low temperature (10 °C) significantly reduced food intake in both tench and goldfish, and neither central nor peripheral administration of galanin or β-endorphin was found to modify feeding. The results indicate that galanin and opioids play a role in the central regulation of feeding in tench, but the stimulatory effect of these neuropeptides did not reverse the feeding inhibition produced by exposure to low temperature.