Population ecological parameters and biomass of anchovy kilka <Emphasis Type="Italic">Clupeonella engrauliformis</Emphasis> in the Caspian Sea

ABSTRACT:   Through most of the last century, three endemic kilka species supported major commercial species in the Caspian Sea. It is clear that catches and abundance of all species have changed, but catch and sampling data are limited and stock assessments are inadequate. Recent changes in the Caspian Sea ecosystem have occurred as a consequence of climatic environmental change (sea level change) and ecologic change caused by the invasive ctenophore Mnemiopsis leidyi . This paper examines the effects of these changes on the population biology and biomass of anchovy kilka Clupeonella engrauliformis in Iranian waters of the Caspian Sea from 1995 to 2004. For most years during this 10-year period, we estimated the age structure of catch, length–weight relationship, von Bertalanffy growth parameters, condition factors, sex ratios, maturity stages determined from ovarian analysis, natural and fishing mortality, age at first capture, and spawning biomass. The instantaneous coefficient of natural mortality was estimated as 0.473/year and the instantaneous coefficient of fishing mortality varied during the 10-year period between 0.541 and 2.690/year. Biomass of anchovy kilka declined from about 186 000 t in 1996 to less than 12 000 t in 2004. Recent high fishing rates were not sustainable after the introduction of Mnemiopsis , so overfishing is part of the explanation for the collapse of anchovy kilka in the Caspian Sea.     

Stock assessment and management implications of anchovy kilka (Clupeonella engrauliformis) in Iranian waters of the Caspian Sea

Recent changes in sea level of the Caspian Sea and ecological impacts caused by the invasive ctenophore (Mnemiopsis leidyi) have altered the ecosystem. A consequence is the changes in the absolute and relative abundance of the commercially important anchovy kilka (Clupeonella engrauliformis) in Iranian waters. To adjust to this change more rigorous management of this fishery is required. This paper examines the maximum sustainable yield (MSY) and fishing intensity at MSY. The paper presents estimates of f_MSY, yield-per-recruit and spawning biomass-per-recruit under various harvest strategies of F_max, F_0.1 and F_40%. We propose a method for estimating acceptable biological catch (ABC) that accounts for large differences in the quality and quantity of information and available data. The MSY and f_MSY were estimated 44,652 mt (metric tons) and 18,609 vessel × nights (a unit of effort). The ABC was estimated at 2190 mt in 2004. In 2005, however, the catch of anchovy kilka was about 4300, over twice the estimated ABC. In 2008 (from January to October) the catch declined to 220 mt. The analyses indicate that overfishing, especially between 2005 and 2008, is the main reason of the collapse of anchovy kilka in the Caspian Sea.     

Incorporation and metabolism of14C-labelled polyunsaturated fatty acids in wild-caught juveniles of golden grey mullet,Liza aurata,in vivo

The incorporation, and the capacity for desaturation and elongation in vivo, of intraperitoneally-injected,¹⁴C-labelled n-3 and n-6 C₁₈ and C₂₀ polyunsaturated fatty acids (PUFA) were investigated in juvenile golden grey mullet,Liza aurata. The results indicate that juvenile mullet have only limited ability to convert C₁₈ polyunsaturated fatty acids to C₂₀ and C₂₂ highly unsaturated fatty acids (HUFA)in vivo. This suggests that juvenile golden grey mullet require the provision of preformed C_20/22 HUFA, such as eicosapentaenoic and docosahexaenoic acids, in the diet. The impairment in the desaturase/elongase pathway was similar to that found in turbot,Scophthalmus maximus, and gilthead sea bream,Sparus aurata, being primarily at the level of Δ5-desaturase. The data from the largely herbivorous golden grey mullet juveniles are consistent with the hypothesis that marine fish in general, irrespective of dietary habits, have limited capacity for the desaturation and elongation of C₁₈ PUFA. The defect in Δ5-desaturase activity combined with the consistent finding that arachidonic acid is selectively incorporated and retained in membrane phosphatidylinositol suggests that, like turbot and gilthead sea bream, golden grey mullet may also have a requirement for preformed arachidonic acid in the diet.     

Lactobacillus spp. bacteria as probiotics in gilthead sea bream (Sparus aurata, L.) larvae: Effects on growth performance and digestive enzyme activities

In this study, the influence of commercial probiotic, Lactobacillus spp., supplementation was investigated on growth parameters and digestive enzyme activities in gilthead sea bream, Sparus aurata, during larval development. All experiments were triplicated and designed in three different administrations of probiotic from 3 days after hatching (DAH) concurrently with starting of exogenous feeding. In the first group, probiotic was added to live food (rotifer and Artemia). In the second group, probiotic was supplemented directly to both live food and water. In the third group, probiotic was added directly to water. Also, no probiotic treatment was maintained in control group. Total bacterial counts among probiotic probiotic-supplemented groups were significantly different from total bacterial counts in controls in water and digestive tract of larvae (p < 0.05). The mean of total bacterial counts in control was approximately 4 × 10⁴-fold increased from the experimental groups in the sea water (p < 0.05). Besides, mean digestive enzyme activities of all probiotics treatment groups were significantly different (p < 0.05) with that of the control. Except probiotic water supplementation group, in all treatments, the specific activities of pancreatic and intestinal enzymes were significantly higher (p < 0.05) in larvae to which probiotic had been supplemented by live food and live food with water. Also, S. aurata larvae that had probiotic administered by live food with water demonstrated significant (p < 0.05) increases in both survival (13–105% higher) and specific growth rate (2–9% higher) as compared to controls. As a result, supplementation of probiotic to directly tank water could not significantly increase growth parameters and digestive enzyme activities and therefore, administration of probiotics by this method would not be effective in terms of husbandry parameters and nutritional condition.     

Effect of Delayed Icing on the Microbiological,Chemical, and Sensory Properties of Caspian Sea Golden Grey Mullet (Liza aurata)

Research has shown that fresh fish is an extremely perishable food as compared to other food commodities. In this study, quality deterioration during storage of golden grey mullet (GGM) iced for 0, 6, and 12 h after landing was monitored. Microbiological indices (total viable count, TVC; psychrophilic counts, PTC; lactic acid bacteria, LAB; and Enterobacteriaceae counts, EBC), chemical parameters (pH; total volatile basic nitrogen, TVB-N; peroxide value, PV; thiobarbituric acid, TBA; and free fatty acids, FFA) values increased over the preicing duration. Delayed icing did not lead to significant increases (p > 0.05) in TVC, PTC, LAB, and EBC throughout the period of storage. All chemical indices increased during storage (p < 0.05). This study showed that sensorial analysis of GGM correlated well with microbiological analysis. Results of this study based on the microbiological and raw fish sensorial data indicated that the shelf life of GGM stored in ice immediately after catch was approximately 10–11 days, while the 6- and 12-h delays in icing shortened the shelf life to approximately 6–7 and 2–3 days, respectively.     

Heritability of skeleton abnormalities (lordosis, lack of operculum) in gilthead seabream (Sparus aurata) supported by microsatellite family data

Body abnormalities constitute an important problem to fish aquaculture. Pigmentation, scale and skeleton abnormalities have been reported in different cultured fish species. Environmental and genetic factors or their interaction have been suggested to explain their origin. Gilthead seabream (Sparus aurata) is one of the most important European cultured species. Lordosis and lack of operculum are common abnormalities in this species, and can reach frequency of 80% or more of commercial batches. In spite of an important body of data suggesting environmental factors related with their origin, scarce and not conclusive genetic data have been reported to date. In our study, a large number of families originating from the usual production process of a commercial farm were used to estimate the heritabilities of both characters. Two independent experiments were carried out for each abnormality. Nine hundred and ninety four (5.6% lordotics; 157 full-sib families; 6.3 offspring/family) and 808 (7.9% lacking operculum; 83 families; 9.7 offspring/family) individuals were used for lordosis and lacking operculum heritability estimations, respectively. The results obtained adjusting an animal model indicated non significant heritabilities for both characters (0.021 (s.e. 0.019) and 0.032 (s.e. 0.023) for lordosis and lack of operculum, respectively). The corresponding values when a threshold model was used, though higher (0.152 and 0.203, respectively), evidenced large standard errors (0.119 and 0.146, respectively) suggesting h² = 0 as the most confident hypothesis (P = 0.838 and 0.766, respectively). A non-parametric permutation test was also applied to evaluate if more related individuals had a higher phenotypic resemblance. The results obtained suggested only a slight familiar association (P < 0.05) when comparing individuals lacking operculum, but neither between lordotics nor between normal ones. These results suggest that most phenotypic variation observed for lordosis and lack of operculum in gilthead seabream is due to environmental factors.     

A geostatistical approach for the stock assessment of the edible sea urchin, Paracentrotus lividus, in four coastal zones of Southern and West Sardinia (SW Italy, Mediterranean Sea)

Quantitative surveys of the edible sea urchin, Paracentrotus lividus, were conducted in four fishing zones of Sardinia (Southern Italy, Mediterranean Sea), in Autumn 2007. A total of 120 stations were geo-located along a bathymetric gradient ranging from 0 to 10 m. A geostatistical method was used to evaluate spatial patterns in density and to estimate harvestable stocks. Variographic analyses showed that the isotropic Gaussian and spherical models successfully explained the spatial structure of sea urchin assemblages in these areas. Density maps obtained by punctual kriging showed that sea urchin populations tend to be patchy rather than uniform in their density distribution. A combination of mapping and size categories was used to generate diverse scenarios of harvestable stocks (specimens ≥50 mm in diameter) before the start of the current fishing season. We conclude that the geostatistical approach, which takes into consideration the spatial autocorrelation structure of the populations in small areas, seems to be a good estimator of P. lividus density and biomass and for the assessment of its harvestable stocks, and thus provides an initial step towards a scientific approach to the management of local sea urchin fisheries.     

Molecular evidence for the lack of transmission of the monogenean Sparicotyle chrysophrii (Monogenea, Polyopisthocotylea) and isopod Ceratothoa oestroides (Crustacea, Cymothoidae) between wild bogue (Boops boops) and cage-reared sea bream (Sparus aurata) and sea bass (Dicentrarchus labrax)

In the Mediterranean area, wild fish have often been suggested as either the reservoirs of the causative agents or at least the carriers of the pathogens responsible for disease outbreaks in cultured fish. However, no epidemiological investigations on actual pathogen/disease interactions between farmed and wild fish have been conducted even for the most important fish pathogens. Only sporadic isolations and identifications of various pathogens in wild fish have been done and real associations with the pathological conditions that exist within the farm environment and vice versa have not been established. Monogenean ectoparasite Sparicotyle chrysophrii and isopod Ceratothoa oestroides are commonly found in the Mediterranean cage-reared sea bream and sea bass and in the surrounding wild fish population. Both species were recognized as pathogens that seasonally inflict serious losses in fingerlings and juveniles of sea bream and sea bass, being potentially propagated and exchanged during wild and caged fish interaction. In order to evaluate the degree of pathogens transfer between wild and farmed fish, we investigated genetic population structures of these two important parasitic pathogens inferred by mtDNA cytochrome oxidase I locus. Parasites isolated from wild and farmed fish on the two most productive Adriatic fish farms showed genetic heterogeneity, contradicting widely accepted hypothesis of cross-contamination, at least in case of S. chrysophrii and C. oestroides. As far as we know, this is the first report that in a study of pathogen transfer molecular evidence was employed to asses the genetic population structure of shared parasites.     

Fecundity and growth-dependent mortality of Pacific anchovy (Engraulis japonicus) in Korean coastal waters

We propose a method of estimating natural mortality of marine pelagic fishes, especially for early-life stages, based on their fecundity. To estimate size-dependent fecundity, growth and mortality of Pacific anchovy (Engraulis japonicus), the most abundant fish species in coastal waters off the Korean peninsula, we undertook a synthesis of results from past studies and data. Assuming that the growth coefficient K varies with water temperature, we derived a modified von Bertalanffy growth equation covering all life stages based on otolith analysis of anchovies collected from southwestern coastal area of Korea in 1996. By revisting a past study on spawning and egg production of anchovies in the southern Korean coastal waters, we calculated a monthly-averaged fraction of mature females spawning per day to estimate that an average female anchovy spawns 36 times per year, and that the mean number of eggs produced by an average female is ca. 160 × 10³ yr⁻¹. Accepting the ‘bigger-is-better’ hypothesis, we derived a theoretical mortality curve that assumes instantaneous natural mortality as an inverse function of anchovy body length. Assuming equilibrium status of stock, estimated annual instantaneous mortality of anchovy between egg to age-1 stage was 11.3 yr⁻¹ and estimated size-specific mortality was 1.24 d⁻¹ mm in fork length. The derived theoretical mortality curve fit well the stage-specific mortalities, which were estimated independently based on ichthyoplankton surveys and anchovy samples collected by commercial nets, but underestimated the egg mortality (0.89 d⁻¹ vs. 0.83 d⁻¹).     

Age, growth and life history of gunnel, Pholis fangi, in the Yellow Sea

We examined the formation of annuli by marginal observations on otoliths of gunnel (Pholis fangi) in the Yellow Sea to validate the age determination method and to derive the growth equation covering from larval to adult stages. Gunnels, ranging from 46 to 173 mm in total length, were collected by a bag net fishery from the western coastal waters off Korea from November 1998 to October 1999. Marginal observations indicated that the translucent zone (annual mark) on adult otolith was formed during the winter, whereas the opaque zone was formed during the summer. However, a translucent zone was formed between May and June in juvenile otoliths. This false ring was formed when the fish transited from the inshore pelagic life of larvae to the offshore bottom life of juveniles. The observed maximum age was 58 months. Using observed length-at-monthly age, growth in length was expressed by von Bertalanffy growth curve; L_t = 144.0 (1 − e^{−0.11 (t+0.43)}). P. fangi spawned in winter recruit to inshore, and grow quickly in the nursery habitats in spring. Gunnel inhabit the bottom offshore area during the summer season, and reappear inshore thereafter.     

莱州湾芙蓉岛人工鱼礁区鮻资源分布特征及其与环境因子的相关性分析

为研究环境因子对人工鱼礁区鰉分布的影响,实验以莱州湾芙蓉岛人工鱼礁区鰉为对象,根据2014—2017年春季和秋季礁区三重刺网调查数据,主要应用GAM模型研究了水温、盐度、pH、溶解氧、饵料生物和人工鱼礁等环境参数以及年份、月份对鰉单位捕捞努力量渔获量(CPUE)和各站位平均体长的影响。结果显示,春季礁区和非礁区CPUE差异不显著,秋季礁区CPUE高于非礁区,是非礁区的3.53倍。礁区和非礁区体长差异不显著。三因素方差分析表明,鰉CPUE受到年份、月份、人工鱼礁、年份和月份的交互作用影响,平均体长则主要受到年份的影响。Delta GAM模型表明,人工鱼礁和水温对CPUE影响显著,鰉在人工鱼礁区出现的概率大于非礁区,随着水温的升高,鰉出现的概率降低;CPUE呈现先升高后降低的趋势,并在8°C达到最高值;饵料浮游植物丰度和浮游动物丰度是影响鰉平均体长的关键因子,当硅藻丰度小于3×10~5个/m~3时,鰉平均体长随硅藻丰度上升而下降,随后趋于稳定;鰉平均体长随浮游动物丰度增加而呈现降低趋势。研究表明,鰉主要分布在秋季水温较低时的人工鱼礁区,体长较大的鰉主要出现在硅藻丰度和浮游动物丰度较低的区域。     

东黄海大黄鱼洄游路线的研究

依据我国10多个主要渔业公司1971-1982年共12年的大黄鱼捕捞统计资料,从产量分布、鱼群移动等方面,研究了东黄海大黄鱼的洄游路线。结果显示,东黄海大黄鱼只有一个种群,两处越冬场。其中,外海越冬场主要位于30°00′N~32°00′N,124°00′E~126°00′E水域,近海越冬场位于浙江中南部和福建北部禁渔线外侧。每年3-4月,外海越冬场鱼群向西进入舟山渔场和长江口渔场;5月,这部分鱼群部分向西北进入吕泗渔场沿海产卵,另一部分向西进入舟山群岛沿海的岱衢洋、大衢洋、黄泽洋和大目洋等水域产卵;到了6月,在长江口和吕泗渔场近海形成索饵群体;6-8月,索饵群体北上黄海南部近海索饵;9月,索饵群体前锋到达34°00′N禁渔线外侧;10月以后,随着冷空气南下,索饵场的大黄鱼向南做越冬洄游,并且在10月回到长江口。从这里,一部分群体游向外海越冬场,一部分群体继续南下回到东海中南部近海的越冬场。浙江中南部和福建北部禁渔线外侧近海越冬的大黄鱼群体,在春季产卵洄游中,部分北上在舟山渔场与外海来的鱼群汇合,进一步游向吕泗渔场和舟山群岛沿海产卵,部分就近游向沿岸的猫头洋、洞头洋、乐清湾、官井洋和东引岛等水域产卵,产卵后的群体在产卵场附近索饵,冬季回到就近的越冬场。     

东、黄海星康吉鳗生长、死亡和单位补充量渔获量

依据2011年、2016年和2017年在东、黄海进行的底拖网调查数据,研究了星康吉鳗的生长参数、死亡系数和单位补充量渔获量(YPR)。星康吉鳗的体长体质量关系和生长方程的拟合结果表明,其条件因子a估计值为4.5×10–4,其异速生长系数b的估计值为3.3。其渐近体长L∞的估计均值为102 cm,生长速率K的均值为0.21/年,理论上体长为零时的年龄t0估计均值为–0.19。通过Pauly经验公式求得星康吉鳗的自然死亡系数(M)为0.33。体长转换的渔获曲线求得总死亡系数为3.36,进而求得现阶段的捕捞死亡系数(F)为3.03,开发率高达90%。此外求得现阶段星康吉鳗的开捕体长为30 cm,对应的开捕年龄为1.47龄,远小于其体质量生长的拐点年龄(3.70龄)和临界年龄(3.39龄)。本研究根据单位补充量渔获量模型,估计其在不同自然死亡系数和开捕体长的情况下随捕捞死亡系数的变化曲线,并估算其生物学参考点。随F增加,YPR先增加到最大值,再逐渐减小。现阶段星康吉鳗的YPR为27.14,而当M为0.33时Fmax估计值为0.38,YPRmax为52.89,即将F降低为1/8,可获得将近2倍的YPR;对应的F0.1为0.255,比Fmax降低了三分之一,YPR0.1(50.38)只比最大值降低了不足5%。M越大,求得的生物学参考点越大,可获得的YPR越小;当开捕体长增加时,F和YPR都会有不同程度的增加。因此,现阶段中国东黄海星康吉鳗的开发率过高,开捕体长过小,处于过度捕捞的状态。为了维持星康吉鳗种群的生态健康、实现该渔业的可持续发展,建议大幅削减其捕捞强度,降低捕捞死亡系数,同时增加开捕体长。     

Relationships between Octopus vulgaris landings and environmental factors in the northern Alboran Sea (Southwestern Mediterranean)

The relationships between environmental factors and fluctuations in Octopus vulgaris landings in the northern Alboran Sea are studied from 1987 to 2007. Landings during this period show both a long term decrease and a strong inter-annual variability. An exploratory phase revealed that local coastal temperatures and those averaged for the whole Alboran Sea during the previous year were the main factors controlling such variability. Warm anomalies have a detrimental effect on the octopus landings on the following year and this suggests that the decreasing trend in octopus landings could be partially linked to the long term warming observed in the Western Mediterranean. It is not yet clear which are the specific mechanisms linking warm anomalies to landing decrease. Nevertheless some hypotheses are proposed and a statistical model is developed for attempting to predict octopus landings one year ahead.     

Brachionus vs Artemia duel: Optimizing first feeding of Upogebia pusilla (Decapoda: Thalassinidea) larvae

Larval rearing of many marine organisms is dependent on the availability of live food. The aim of this study was to optimize larval first feeding for the mud shrimp Upogebia pusilla, by comparing the effectiveness of the two most commonly used live feeds: Brachionus plicatilis and Artemia sp. nauplii. Survival, larval duration, molt synchronism and megalop size were compared using five feeding treatments: Artemia from zoea I to IV (B0), Brachionus during zoea I and Artemia from zoea II to IV (B1), Brachionus during zoea I and II and Artemia during zoea III and IV (B2), Brachionus from zoea I to III and Artemia during zoea IV (B3) and Brachionus from zoea I to IV (B4). The proportion of larvae that reached the megalop stage was 0.00% in treatment B0, 3.33% in treatment B1, 33.33% in treatment B2, 66.67% in treatment B3 and 76.67% in treatment B4. Larvae fed on rotifers until zoea III or zoea IV stages had a higher survival but no differences were found either in time to reach megalop or in megalop size. This study demonstrates that rotifers are essential for the survival and development of U. pusilla early larval stages but that rotifers can be successfully replaced by Artemia nauplii in the zoea IV stage.     

Cryoprotectant microinjection toxicity and chilling sensitivity in gilthead seabream (Sparus aurata) embryos

Cryopreservation of fish embryos requires an optimal distribution of cryoprotectants inside all embryo compartments. Traditional techniques for the incorporation of cryoprotectants (CPAs) have failed to protect all fish compartments, especially the yolk sac which has been considered the principal point of embryo chilling sensitivity. In the present study, microinjection was used to incorporate cryoprotectants into the yolk sac of gilthead seabream (Sparus aurata) embryos at tail bud stage. The effect of microinjection viability, cryoprotectant toxicity and chilling resistance was evaluated through the hatching rate. Larval survival at first feeding was also determined in microinjection viability and cryoprotectant toxicity studies. Permeabilized seabream embryos were microinjected with 2.35 nl dimethyl sulfoxide (Me₂SO), methanol (MeOH), ethylene glycol (EG) (5 M, 10 M and pure) or sucrose (10% and 15%). In a second experiment, 29.5 nl and 154.0 nl of the highest concentration of each cryoprotectant were used in the same embryo stage. To test the effect of microinjected cryoprotectants on embryo chilling resistance, 29.5 nl of pure Me₂SO or 15% sucrose was microinjected into the yolk sac of tail bud stage embryos and then at a later stage, (tail-bud-free), were exposed to 3 M Me₂SO solution at − 10 °C for 30 min. Our results showed that microinjection technique did not affect the viability of tail bud stage embryos as is shown by the high hatching and survival rates. Hatching and larval survival rate at first feeding were not affected with any of the CPAs tested, showing percentages higher than 75% and 90%, respectively, when embryos were microinjected with a smaller quantity of cryoprotectant. Sucrose was the cryoprotectant better tolerated at higher concentration and volume. Cryoprotectant concentration inside the yolk higher than 1.18 M for Me₂SO, 1.5 M for EG and 2 M for methanol decreased the hatching rate. Microinjection allowed the delivery of high concentrations of CPAs into the yolk sac without deleterious effects on the embryo, but did not provide a significant level of protection for the whole embryo against chilling injury.     

An assessment of the west winter–spring cohort of neon flying squid (Ommastrephes bartramii) in the Northwest Pacific Ocean

In the Northwest Pacific, the squid jigging fisheries targeted the west winter–spring cohort of neon flying squid (Ommastrephes bartramii) from August to November. Total annual catch by the Chinese mainland squid jigging fleet during 2000–2005 ranged from 64,100 to 104,200 t. The unique life history of this squid species makes the use of traditional age- or length-structured models difficult in evaluating the effect of intensive commercial jigging on this stock. We fitted a modified depletion model to the Chinese jigging fisheries data to estimate the squid stock abundance during 2000–2005. Monthly biological data were randomly sampled from the five squid jigging vessels during the fishing seasons. Effects of using different natural mortality rates (M) and three different error assumptions were evaluated in fitting the depletion model. Based on sensitivity analyses, the log-normal error model was found to be preferred for the squid assessment. The assessment results indicated that the initial (pre-fishing season) annual population sizes ranged from 199 to 704 million squid with the M value of 0.03–0.10 during 2000–2005. The proportional escapement (M = 0.03–0.10) for different fishing seasons over the time period of 2000–2005 ranged from 15.3% (in 2000) to 69.9% (in 2001), with an average of 37.18%, which was close to the management target of 40%. Thus, the current fishing mortality of the squid jigging fishery was considered to be sustainable. We inferred its annual maximum allowable catch ranging from 80,000 to 100,000 t. This study suggests that the modified depletion model provides an alternative method for assessing short-lived species such as O. bartramii.     

Ontogeny of the digestive tract of thick lipped grey mullet (Chelon labrosus) larvae reared in “mesocosms”

This work describes the ontogeny of the digestive tract in thick lipped grey mullet (Chelon labrosus) larvae reared until day 36 post-hatching with the semi-extensive technology in mesocosms. Diet was constituted by live preys, rotifers, Artemia and wild zooplankton, then compound diet was added from day 20 (p. h.). Linear growth, weight growth and digestive enzymes specific activities were studied during larval ontogeny. Pancreatic enzymes (trypsin and amylase) and intestinal enzymes (leucine-alanine peptidase “Leu-ala”, aminopeptidase N “AN” and alkaline phosphatase “AP”) were assayed in larvae sampled throughout the rearing trial to evaluate gastrointestinal maturation along the development.The trypsin specific activities were very high during the first two weeks and then declined as observed in marine fish species. A following increase in trypsin specific activity from day 20 was attributed notably to ingestion of particle compound diet. In contrast to the pattern generally described in fish larvae, amylase specific activity showed a continuous increase. This could be attributed to the fact that C. labrosus is an omnivorous species and suggests that the fish might be able to use efficiently diets containing higher levels of starch or other carbohydrates since the end of larval development.Relative expression of intestinal brush border membrane enzymes (AP and AN) and cytosolic enzyme (Leu-ala), showed an abrupt increase of both AP/leu-ala and AN/leu-ala ratios at day 8 (p. h.), indicating that maturation of intestinal tract in C. labrosus larvae is particularly precocious. It is assumed that larvae of C. labrosus might support early co-feeding and weaning strategies, which could reasonably be initiated since mouth opening.     

CYP3A65及上游核受体基因PXR和AHR2在斑马鱼生长发育阶段的表达

为了选择处于最佳生长阶段的斑马鱼用于药物代谢研究,本实验考察不同生长阶段斑马鱼全鱼、肝脏和肠道组织中CYP3A65及其上游核受体基因(PXR、AHR2) mRNA表达水平的变化规律。实验测定CYP3A65、PXR和AHR2相对表达量,并通过比较核受体基因与代谢酶基因mRNA之间的相关性来证实核受体基因的调控作用。结果显示,144 hpf和75 dpf两个生长阶段的斑马鱼中CYP3A65、PXR和AHR2 mRNA表达量最高;斑马鱼生长阶段中代谢酶基因和核受体基因的表达趋势一致,且受肝脏、肠道组织占全鱼比重的影响。研究表明,幼鱼期144 hpf斑马鱼及稚鱼期75 dpf的斑马鱼最适用于CYP3A65代谢研究;CYP3A65与PXR、CYP3A65与AHR2的mRNA表达之间有显著的相关性,与AHR2的相关性更显著。     

中国南海西沙群岛海域鸢乌贼耳石微结构及生长特性

耳石是头足类重要的硬组织,被广泛用于研究头足类的年龄与生长、种群结构和生活史等。根据我国灯光罩网渔船2016年1—3月和2017年1—3月在中国南海西沙群岛海域调查生产期间采集的鸢乌贼样本,测量了513枚鸢乌贼耳石外部形态参数(雌性276枚、雄性237枚),结合耳石的日轮数据,对西沙群岛海域鸢乌贼耳石的微结构及其生长特性进行了研究。主成分分析显示,耳石总长(TSL)、最大宽度(MW)、侧区长(LDL)和翼区长(WL)可以作为鸢乌贼耳石外形生长的特征参数。协方差分析表明,耳石的特征参数与日龄、与胴长的生长均不存在性别间显著性差异,TSL、MW和LDL与日龄的关系均最适合用幂函数表示,与胴长的关系则均最适合用对数函数表示。TSL、MW和LDL的绝对和瞬时相对生长率均随着日龄的增加而呈现先增加、后减少的趋势,且在181～210 d分别达到峰值,因此,181～210 d可能是鸢乌贼耳石外形生长的拐点。