Performance of single-drain and dual-drain tanks in terms of water velocity profile and solids flushing for in vivo digestibility studies in juvenile shrimp

In vivo digestibility determination in shrimp is a challenge because these animals are coprophagous, benthic and slow feeders and the small amount of feces that they produce is difficult to collect. The objective of this study was to evaluate an efficient tank design for the purpose of studying shrimp digestibility. Different tank designs were evaluated considering drain system (dual-drain and single-drain), water inlet flow rate (8, 12, and 16 L min⁻¹) and bottom drain diameter (6, 13, 19, 25 and 50 mm) and their effects on tank hydraulics, water velocity and solids flushing. A circular and slightly conical 500 L tank was adapted with a clarifier for the two dual-drain designs (Cornell-type and central-type) and settling columns for the two single-drain designs (Guelph-F and Guelph-L). Results showed that: (1) water rotational velocity profile was more homogeneous in tanks with larger bottom drain outlets, and water velocity increased with water inlet flow rate from almost zero up to 14.5 ± 0.7 cm s⁻¹; (2) solids flushing, measured as the percentage of feed pellets retained at both the bottom drain and in the settling devices, was positively correlated with the surface loading rate (L min⁻¹ flow per m²) and was more effective at the Guelph-L design fitted with a 150 mm diameter settling column. In this system 100% of the solids were removed at the inflow rate of 16 L min⁻¹. It can be concluded that among the systems evaluated, the Guelph-L at an inflow-rate of 12 L min⁻¹ was most efficient for both solids removal and water velocity profile and thus seemed more suitable for shrimp digestibility studies in high performance conditions. Technologies involving hydrodynamic must be intensively applied to solids removal for aquatic species production as well as research purposes like digestibility, which is highlighted in this study.     

Settling velocity and particle size bioengineering parameters gathered from solids generated by wild-caught premature punctuated snake-eels (Ophichthus remiger) reared in a marine prototype recirculating aquaculture system

This research reveals the applied engineering basis for determining the particle size and settling velocity distributions of solids generated while rearing wild-caught premature punctuated snake-eels (Ophichthus remiger) in a prototype recirculating aquacultural system. Settled solids were sampled from the bottom of the rearing tanks, and suspended solids were sampled before filtration within the drum filter and analyzed to characterize their settling velocity and particle size properties. These particle properties are considered bioengineering parameters since they will provide biological information to improve engineering solutions for RAS solids removal processes. The average settling velocity for the settleable solids in the rearing tanks was 2.89 ± 0.02 cm s⁻¹, and the average particle size ranged between 7.32 ± 3.41 and 19.44 ± 8.58 mm. Suspended solids within the drum filters before filtration had an average settling velocity of 0.35 ± 0.11 cm s⁻¹ and it was found that 69.93 % of the particles size was greater than 200 μm, 15.40 % were within the range of 120 μm and 90 μm sizes, and 6.53 % were between 70 μm and 40 μm sizes. The particle physical properties, settling curves, and particle sizes curves obtained from this experience represent valuable information to be used to improve engineering design of solids handling mechanisms, especially in marine land-based systems, and in this case, applied for rearing wild-caught punctuated snake-eels. The present investigation constitutes an advance in the knowledge of applied engineering to the design of a marine aquaculture fattening operation targeted to feed up wild-caught premature punctuated snake-eels to the point of sale or trade.     

Brook trout (Salvelinus fontinalis) movement and survival after removal of two dams on the West Branch of the Wolf River,Wisconsin

Dam removals allow fish to access habitats that may provide ecological benefits and risks, but the extent of fish movements through former dam sites has not been thoroughly evaluated for many species. We installed stationary PIT antennas in 2016 and 2017 to evaluate movements and survival of brook trout Salvelinus fontinalis in the West Branch of the Wolf River (WBWR) in central Wisconsin following removal of two dams and channel modifications designed to promote fish movement. These changes provided access to lacustrine habitats that might provide suitable winter habitat or act as ecological sinks. We used multistate models to estimate transition probabilities between river sections, to determine whether brook trout: (a) moved between multiple river sections and (b) entered lacustrine habitats as seasonal refuges, but eventually returned to lotic habitat. We also used a Cormack-Jolly-Seber model to evaluate whether apparent survival of brook trout in the WBWR was comparable to other populations. Few fish moved among river sections or used lacustrine habitat (<5% of tagged fish); most brook trout remained in sections where they were initially tagged, potentially due to quality habitat located throughout the river. Like other studies, brook trout in the WBWR appear to experience high mortality based on low number of detections, few physical recaptures and an estimated eight-month apparent survival rate of 0.27. In scenarios where fish can already access suitable habitat, removal of dams may not result in substantial increases in fish movement and colonisation of newly accessible habitat may not occur immediately.     

中间球海胆卵膜与受精膜去除方法及染色体核型分析

去除卵膜及受精膜是成功制备棘皮动物染色体的关键步骤。为找到高效去除海胆卵膜与受精膜的方法,使用三氮唑（2 g/L）、盐酸海水溶液（pH 4.75）、二硫苏糖醇（3×10^-3 mol/L）和对氨基苯甲酸（3×10^-3 mol/L）等4种化学试剂分别对中间球海胆（）卵子及各时期胚胎进行处理,比较了不同试剂、处理时间或处理时期的去膜率、去膜后受精率和胚胎畸形率等指标的差异;利用常规空气干燥法对经去膜处理的囊胚期胚胎制备染色体,并进行核型分析。结果表明,三氮唑、盐酸海水溶液、二硫苏糖醇和对氨基苯甲酸等4种试剂对中间球海胆的卵膜和受精膜均有去除效果,其中2 g/L三氮唑处理未受精卵30 min的去膜率为85.50%,去膜后受精率为97.25%,畸形率为1.75%,去膜效果优于其余处理组。利用经该方法去膜后的早期囊胚进行染色体制备效果较好,获得了61个分散良好、形态完整的染色体中期分裂相。核型分析表明,中间球海胆的二倍体染色体数为2n=42,核型公式为：2n=20m+20sm+2st,NF=84,即有10对中部着丝粒染色体,10对亚中部着丝粒染色体,1对亚端部着丝粒染色体,染色体臂数为NF=84。本研究可为海胆染色体制备及染色体操作育种提供技术参考。     

Water quality dynamics and shrimp (Litopenaeus vannamei) production in intensive, mesohaline culture systems with two levels of biofloc management

A dense microbial community develops in the water column of intensive, minimal-exchange production systems and is responsible for nutrient cycling. A portion of the microbial community is associated with biofloc particles, and some control over the concentration of these particles has been shown to provide production benefits. To help refine the required degree of control, this study evaluated the effects of two levels of biofloc management on water quality and shrimp (Litopenaeus vannamei) production in commercial-scale culture systems. Eight, 50 m³ raceways were randomly assigned to one of two treatments: T-LS (treatment-low solids) and T-HS (treatment-high solids), each with four replicate raceways. Settling chambers adjacent to the T-LS raceways had a volume of 1700 L with a flow rate of 20 L min⁻¹. The T-HS raceways had 760 L settling chambers with a flow rate of 10 L min⁻¹. Raceways were stocked with 250 shrimp m⁻³, with a mean individual weight of 0.72 g, and shrimp were grown for thirteen weeks. Raceways in the T-LS treatment had significantly reduced total suspended solids, volatile suspended solids, and turbidity compared to the T-HS treatment (P ≤ 0.003). The T-LS raceways also had significantly lower nitrite and nitrate concentrations, and the T-HS raceways had significantly lower ammonia and phosphate concentrations (P ≤ 0.021). With the exception of nitrate, there were no significant differences between the change in concentration of water quality parameters entering and exiting the settling chambers in the T-LS versus the T-HS treatment. Nitrate never accumulated appreciably in the T-LS raceways, possibly due to denitrification in the settling chambers, bacterial substrate limitations in the raceways, or algal nitrate assimilation. However, in the T-HS raceways nitrate did accumulate. The T-HS settling chambers returned a significantly lower nitrate concentration and significantly greater alkalinity concentration than what entered them (P ≤ 0.005), indicating that denitrification may have occurred in those chambers. There were no significant differences in shrimp survival, feed conversion ratio, or final biomass between the two treatments. However, shrimp in the T-LS treatment grew at a significantly greater rate (1.7 g wk⁻¹ vs. 1.3 g wk⁻¹) and reached a significantly greater final weight (22.1 g vs. 17.8 g) than shrimp in the T-HS treatment (P ≤ 0.020). The results of this study demonstrate engineering and management decisions that can have important implications for both water quality and shrimp production in intensive, minimal-exchange culture systems.     

响应面法优化罗氏海盘车生殖腺皂甙脱除技术研究

利用紫外分光光度计全扫描模式确认罗氏海盘车生殖腺皂甙检测波长,利用响应面法对生殖腺皂甙脱除条件进行优化。利用响应面Box-Bohnken法优化生殖腺皂甙脱除条件,各条件取整数,超声时间13min、乙醇体积分数4.5%、脱除次数2,进行3次验证试验,残渣中皂甙平均含量为0.094mg/g,与模型预测值接近,与处理前0.325mg/g对比,脱除率达72.3%,说明海盘车生殖腺皂甙脱除模型建立成功。     

Water quality,Vibrio density and growth of Pacific white shrimp Litopenaeus vannamei (Boone) in an integrated biofloc system with red seaweed Gracilaria birdiae (Greville)

An indoor trial was conducted for 42 days to evaluate water quality, Vibrio density and growth of Litopenaeus vannamei in an integrated biofloc system (IBS) with Gracilaria birdiae. Four treatments were used, each in triplicate: Control (monoculture shrimp); IBS 2.5 (L. vannamei and 2.5 kg wet weight seaweed m^?3); IBS 5.0 (L. vannamei and 5.0 kg wet weight seaweed m^?3) and IBS 7.5 (L. vannamei and 7.5 wet weight seaweed m^?3). Shrimp individuals (0.34 ± 0.01 g) were stocked at a density of 500 shrimp m^?3. No water exchange was carried out during the experimental period. Molasses was added once a day as an organic carbon source to maintain the C:N ratio at 12:1. The IBS significantly decreased (P < 0.05) dissolved inorganic nitrogen (DIN) ranging from 19% to 34% (3.12–3.83 mg L^?1), NO₃‐N ranging from 19% to 38% (2.40–3.16 mg L^?1), Vibrio density ranging from by 8–83% (0.40–2.20 log 10³ colony‐forming units mL^?1), and FCR ranging from by 20–30% (1.20–1.37), as compared to the control (4.73 mg L^?1, 3.93 mg L^?1, 2.40 log 10³ colony‐forming units mL^?1, and 1.74 respectively). Moreover, the IBS significantly increased (P < 0.05) crude protein in whole body shrimp, ranging from 8% to 13% (13.2–13.7% wet weight basis); as well as final weight, ranging from 25% to 32% (3.90–4.12 g), weekly growth ranging from 25% to 34% (0.59–0.63 g), and shrimp yield by 22–39% (1.72–1.96 kg m^?3), as compared to control (12.1% wet weight basis, 3.12 g, 0.47 g, and 1.41 kg m^?3 respectively). It can thus be concluded that cultivating Gracilaria birdiae in an IBS with L. vannamei can contribute to DIN and NO₃‐N removal, lower Vibrio density, increased crude protein in whole body shrimp, higher growth and yield parameters in shrimp culture.     

Changes in the density and growth of brown trout (Salmo trutta) after intensive removal of sympatric Arctic charr (Salvelinus alpinus) in the sub‐Arctic lake Møkkelandsvatn,Norway

This study tests the basic hypothesis that the removal of charr, Salvelinus alpinus (L.), would cause an increase in both the growth and density of a sympatric trout population, Salmo trutta L. The charr population was characterised by slow‐growing individuals, with a high proportion of mature fish, that is typical for so‐called overpopulated populations. A total of 31,000 charr was removed from the lake in the period 1990–1992, and the density of younger trout (1+, 2+), but not older trout (3+, 4+), increased. The growth of older trout (3+, 4+) increased, but the evidence for similar growth increases of younger trout (1+, 2+) was limited. From 1989 to 1990, the proportion of trout increased from 30 to only 40% of the total catch, but from 1991 to 1994, it was significantly higher (60–80%) than that of charr. Total trout biomass increased to a maximum in 1992 and then decreased so that the biomass of 1994 was nearly similar to that of 1989, that is before the start of the charr removal. Back‐calculated lengths of trout from otoliths showed that 2+ and 3+ trout caught in the pelagic were growing consistently faster over previous years than those caught in the littoral, while this was not the case for the 4+ fish. Therefore, the hypothesis was partially supported; the growth rate of trout increased (age groups 1+ to 4+), while the density of juvenile trout (1+, 2+), but not the older trout (3+, 4+), increased after the removal of charr.     

The impacts of aquacultured oysters, Crassostrea virginica (Gmelin, 1791) on water column nitrogen and sedimentation: results of a mesocosm study

To determine effects of aquacultured oysters Crassostrea virginica (Gmelin, 1791) on the overlying water column, a mesocosm study was performed at the Marine Ecosystem Research Laboratory (MERL) from June to October, 2000. The MERL facility is located adjacent to Narragansett Bay and consists of fourteen 13,000-l mesocosm tanks designed to simulate the Bay environmental conditions. Two hundred oysters (≈35 mm valve height; nominally filtering about 55 l/day/individual) were placed into three mesocosms, and three mesocosms were maintained without oysters as controls. Experiments were run with varying rates of water exchange in the tanks ranging from 0% to 100% per day (13,000 l/day). Parameters that were measured and compared between the two treatments included chlorophyll-a, particulate organic and inorganic matter, sedimentation, nitrate, ammonia, selected phytoplankton species and oyster growth rates. Oysters affected phytoplankton species composition and increased rates of sedimentation. Large diatoms were net sampled, and Nitzchia striata was predominant in mesocosms with oysters, while Skeletonema costatum dominated the control tanks. Ammonia excretion rates were determined for C. virginica using the salicylate–hypochlorite method. Ammonia excretion can be described by the allometric equation E=50.65w^0.699 when E is the ammonia excretion rate in μg/h, and w is the soft tissue dry weight in grams. Based on rates of ammonia excretion by oysters and observed steady states of ammonia and other forms of inorganic nitrogen in mesocosm tanks, it can be hypothesized that ammonia generated by oysters is taken up by rapidly regenerating phytoplankton in the water column.     

Use of MS‐222 (tricaine methanesulfonate) and propofol (2,6‐diisopropylphenol) as anaesthetics for the tetra Astyanax altiparanae (Teleostei,Characidae)

The aim of this study was to evaluate the anaesthetic effect of MS‐222 and propofol and determine their optimal concentrations for safe handling of the tetra Astyanax altiparanae in the laboratory. The fish were separated by length into three classes: I (1.5–5.0 cm), II (5.1–8.0 cm) and III (greater than 8.1 cm). Pilot tests were performed to evaluate the appropriate anaesthetic concentrations for inducing the five possible anaesthetic stages: I – sedation; II – light anaesthesia; III – deep anaesthesia; IV – surgical anaesthesia; and V – spinal collapse. After defining the maximum and minimum concentrations required to induce stage IV anaesthesia, the animals were exposed to five intermediate concentrations (n = 10 fish/concentration) of each anaesthetic for 15 min. The animals were then transferred to clean water to evaluate the time required for recovery. In addition, blood glucose levels were measured for class II and class III fish subjected to the previously defined ideal concentrations for each of the tested anaesthetics (n = 10 fish/treatment). Both evaluated substances are suitable to anaesthetize A. altiparanae. The optimal MS‐222 concentration was 90 mg L^?1, and this result was similar for all three size classes. The optimal propofol concentrations for inducing surgical anaesthesia in the size classes I, II and III were 0.22, 0.23 and 0.27 respectively.     

Effect of pressure and pH in ammonium retention for nanofiltration and reverse osmosis membranes to be used in recirculation aquaculture systems (RAS)

Recirculation systems are becoming widely used in the aquaculture industry, where ammonium removal results are crucial for a proper performance considering its high toxicity on fish. The objective of this study was to assess the ammonium retention, when the transmembrane pressure (TMP) in nanofiltration (NF) and reverse osmosis (RO) membranes are changed. Two pH levels were tested: pH 5, where ammonium is as NH⁴⁺, and pH 7 which is an average of the most common range in aquaculture (pH 6-8). In this study a model solution of ammonium-water and commercial membranes of polyamide supplied by Alfa Laval (DSSHR98PP) and Dow (NF90, NF200 and NF270) were used, with a membrane area of 0.01018 m². A critical TMP was determined, where the repulsive electrochemical forces at the active layer were exceeded by the transmembrane pressure, causing an irreversible decrease of the retention values. The maximum TMP values for NF and RO membranes were 16 bar and 24.5 bar, respectively. Ammonium retention at pH 7 was higher than pH 5 for all assessed membranes before the critical TMP was reached, with average values of 100, 99.7, 98.4 and 87.5% for membranes NF90, DSSHR98PP, NF200 and NF270, respectively. It may be concluded the ammonium retention mechanism in the studied membranes basically corresponds to an electrochemical mechanism, where pH and critical TMP influence the retention values of ammonium.     

Modelling the reestablishment of coho salmon (Oncorhynchus kisutch) in Klamath River tributaries after dam removal

The planned removal of four dams on the Klamath River (anticipated 2024) will be the largest river restoration effort ever undertaken on the planet. Dam removal will restore access to >50 km of the Klamath River mainstem for coho salmon, but mainstem habitat may not be suitable for rearing juvenile coho salmon. Instead, small tributaries may provide most rearing habitat for reestablishing coho salmon. We used four approaches to evaluate six Klamath River tributaries above existing dams to assess their potential to support juvenile coho salmon: (1) We measured summer temperature regimes and evaluated thermal suitability. (2) We applied an Intrinsic Potential (IP) model to evaluate large-scale geomorphological constraints on coho salmon habitat. (3) We used the Habitat Limiting Factors Model (HLFM) to estimate rearing capacity for juveniles given current habitat conditions. (4) We developed an occupancy model using data from reference tributaries to predict coho salmon rearing distribution. All six streams had summer temperatures cooler than the mainstem Klamath River. However, five of the streams have barriers that will restrict coho salmon to within 5 km of the confluence with the Klamath River and two were disconnected mid-summer. Despite these constraints, the tributaries will likely produce coho salmon. Most streams had high IP in their lower reaches, the HLFM model estimated a total capacity of 105,000 juvenile coho salmon, and the occupancy model predicted juvenile coho salmon will rear throughout the accessible reaches. Protection and habitat enhancement for these tributaries will be important for coho salmon reestablishment post-dam removal.     

Practical applications of low-pressure hydrocyclone (LPH) for feed waste and fecal solid removal in a recirculating aquaculture system

In this work, the practical application of a low-pressure hydrocyclone was examined for feed waste and fecal solid removal for common carp (27 ± 3.1 g, average ± SD) and Nile tilapia (33 ± 3.4 g, average ± SD) in a recirculating aquaculture system. The dimensions of the low-pressure hydrocyclone included an inflow diameter of 30 mm, a cylinder length of 575 mm, an overflow diameter of 60 mm, an underflow diameter of 50 mm, a cylinder diameter of 335 mm and a cone angle of 68°. The different operating conditions tested were inflow rates of 400, 600, 800 and 1000 ml s⁻¹, and underflow rates of 25%, 25%, 20% and 10% of the inflow rates, respectively. Feed waste totals of 4.1 to 4.8% and 3.6 to 4.0% of the feed intake were produced by the common carp and Nile tilapia, respectively. The maximum separation efficiency (Et) for the feed waste from the common carp was 71% at an inflow rate of 600 ml s⁻¹ with an underflow rate of 25% of the inflow rate. The maximum separation efficiency for the feed waste from the tilapia was 59% at an inflow rate of 400 ml s⁻¹ with an underflow rate of 25% of the inflow rate. The fecal solid production estimated from the digestibility was 37.9% and 35.7% of the feed intake for the common carp and Nile tilapia, respectively. The maximum separation efficiency for the feces from the common carp was 60% for an inflow rate of 600 ml s⁻¹ and an underflow rate of 25% of the inflow rate. The maximum separation efficiency for the tilapia feces was 63% at an inflow of 400 ml s⁻¹ with an underflow rate of 25% of the inflow rate. The low-pressure hydrocyclone can be adopted for prefiltration and/or post-filtration for the removal of various sized solids. Furthermore, the solids separated from the underflow can be easily removed for further processing.     

Mathematical model for goldfish recirculating aquaculture system (GRAS)

A mathematical model is framed for a goldfish recirculating aquaculture system based on unsteady-state mass balance for prediction of the concentration of total ammonia nitrogen (TAN), nitrite-nitrogen (NO₂-N), nitrate-nitrogen (NO₃-N), dissolved oxygen (DO) and total suspended solids (TSS). The goldfish were stocked at 100 numbers per m³ of rearing water volume of 5 m³ tank capacity in the years 2009 and 2010 and the model was calibrated and validated. The recirculation flow rate was fixed at 29,000 L/day. The model parameters were estimated as k_TAN (mg of TAN generated per kg of feed): 20,000, M (mortality rate): 0.002 day⁻¹, α (percentage of feed conversion to suspended solids): 23.8, k_oxy (mg of oxygen required for fish respiration per kg of feed applied in unit time): 300,000, k_b (partial nitrification in the culture tank): 0.86 and the reaction rate constants, k₁ and k₂: 84.65 day⁻¹ and 42.03 day⁻¹ respectively and temperature growth coefficient (TGC): 5.00 × 10^-5. The model efficacy was adjudged by estimation of the coefficient of determination (R²), root mean square error (RMSE), Nash-Sutcliffe modelling efficiency (E_NS) and graphical plots between predicted and observed values.     

Separation of fine organic particles by a low-pressure hydrocyclone (LPH)

The separation performance of a low-pressure hydrocyclone was tested using fine organic particles from 1 to 700 μm. The dimensions of the low-pressure hydrocyclone were an inflow diameter of 30 mm, a cylinder length of 575 mm, an overflow diameter of 60 mm, an underflow diameter of 50 mm, a cylinder diameter of 335 mm and a cone angle of 68°. The low-pressure hydrocyclone was operated with a lower inlet pressure (average 1.38–5.56 kPa) that could be maintained under water level differences that ranged from 17.5 to 53.5 cm between the water surface of the feeding mass cylinder and the middle of the inlet pipe of the low-pressure hydrocyclone. By varying the inflow rate, underflow ratio and feed concentration, the separation performance of the low-pressure hydrocyclone was affected. The separation performances were determined from total separation efficiency and grade efficiency. Separation performances were determined according to the different inflow rates of 400, 600, 800 and 1000 ml s⁻¹ and their respective underflow ratios that ranged from 5% to 30%. The maximum total separation efficiencies for each inflow rate were 41%, 46% and 46% at 400, 800 and 1000 ml s⁻¹ inflow rates, respectively, and at underflow rates of 30% of the inflow rates. In addition, a total separation efficiency of 46% was employed at 600 ml s⁻¹ of inflow rate and with an underflow rate of 25% its inflow rate. As the feed concentration increased from 25 to 150 mg l⁻¹, the separation performances were gradually decreased. For the fine particles ranging 1–200 μm, the grade efficiency was higher at the higher inflow rate (higher than 600 ml s⁻¹) and higher underflow rate. However, for the coarse particles ranging 400–700 μm, the grade efficiency was higher at the lower inflow rate (lower than 600 ml s⁻¹) and higher underflow rate. The cut-point (d₅₀) values ranged from 30 to 200 μm for a feed size range of 1–700 μm. The Response Surface Method (RSM) model predicted an optimum operating inflow rate and underflow ratio of 721 ml s⁻¹ of inflow rate and 30%, respectively, for the low-pressure hydrocyclone at a maximum total separation efficiency. Based on these findings, further design and operating adaptation of low-pressure hydrocyclones used for fine solids removal in recirculating aquaculture systems is expected.     

Testing the efficacy of bouncing-bucket nursery systems for enhancing shell strength and thickness in on-bottom cultured Eastern oysters (Crassostrea virginica)

Through physical manipulation, oyster growers can modify the morphological features of young oysters in order to improve their robustness and resiliency to predation. In this study, the efficacy of a novel passive culturing technique using floating buckets that “bounce” oysters prior to the benthic grow-out phase for enhancing shell thickness and strength, while not compromising oyster shape, was investigated. Using a field experiment, we quantified and compared the shell thickness (mm), compressive strength (Newtons), and shape (fan ratios and cup ratios) of juvenile oysters subjected to this bouncing technique with oysters grown in floating bags, the current industry standard. Results indicated that bouncing increased shell thickness and strength for oysters >45 mm shell height compared to control oysters, but also decreased shell thickness and strength for oysters <45 mm shell height compared to control oysters. There was no difference in shell shape between bounced and control oysters, with both groups having similar fan and cup ratios. Ultimately, our results suggest that the size at which bounced oysters are released to the benthos for grow out will dictate the usefulness of bouncing technique for reducing predation-related mortality.     

Optimized biophysical model for Icelandic cod (Gadus morhua) larvae

A characteristic of biophysical models (BPM) is that they contain a number of parameters that are poorly known or only known within a range of possible values. This paper describes an efficient optimized BPM developed to simulate the Icelandic cod pelagic 0‐group survey data. The method is based on presenting the results as a probability density function (PDF) that a particle released from a given spawning drifts downstream to a given grid location some time later. The model determines egg production model parameters (peak spawning time, spawning duration, number of eggs released) for each of 15 spawning grounds as the solution of a bound constrained optimization problem that minimizes model‐data misfits in abundance and age distributions. The model is applied to simulating the 2002 and 2003 summer survey data. The model does a reasonable job of simulating the observed inshore / offshore abundance gradient and spatial age gradient for each year. Problem areas are explained from the point of view of model limitations. We caution that the results from an optimized model should always be assessed with the model’s limitations in mind and with respect to whatever biological data are available.     

长江天鹅洲故道银鮈年龄、生长和死亡率的研究

根据2011年3月至2012年1月在长江天鹅洲故道采集的银鮈(Squalidus argentatus)样本873尾,用鳞片为年龄鉴定和生长退算材料,研究银鮈的年龄、生长特性及死亡率.结果表明,雌雄群体均由1～6龄组成,雌鱼87.35％为1～3龄,雄鱼87.01％为1～3龄.雌雄鱼体长(L)和体重(W)关系表现为异速生长,雌鱼w=0.009L3.2285,雄鱼w=0.009L3.2254.以退算体长拟合von Bertalanffy方程,得到生长参数为:雌鱼L∞=17.1797cm,k=0.1820,t0=-1.2673和雄鱼L∞=11.5069cm,k=0.4074,to=-0.5764.雌雄鱼的自然死亡率分别为M=0.6048/a和M=1.1459/a,远高于一般鱼群自然死亡率(M=0.2～0.3/a);开发率分别为E=0.5711和E =0.4183.长江天鹅洲故道银鮈雌鱼处于过度开发的状态,应加强管理.     

应用贝叶斯状态空间剩余产量模型框架评估印度洋大眼金枪鱼的资源状况

根据1950―2016年的渔获量数据及1955―2016年的单位捕捞努力量(Catch Per Unit Effort,CPUE)数据,采用贝叶斯状态空间剩余产量模型框架JABBA(Just Another Bayesian Biomass Assessment)对印度洋大眼金枪鱼(Thunnus obesus)的资源状况进行评估,分析了渔船效应、CPUE数据尺度对评估结果的影响。结果表明,模型拟合效果对于不同时间跨度下CPUE数据的选择比较敏感。当选用时间跨度为1979―2016年的CPUE数据且考虑渔船效应时,模型拟合效果最好。2016年大眼金枪鱼的资源量为812 kt,最大可持续产量(Maximum Sustainable Yield,MSY)为163 kt,远高于同年渔获量86.81 kt,其资源量具有82.50%的概率处于"健康"状态。当总允许可捕量为69.45～104.17 kt时(2016年渔获量的80%～120%),未来10年大眼金枪鱼的资源量仍高于B_(MSY)(达到MSY所需的生物量)。回顾性分析结果表明,该资源评估结果存在一定程度的回顾性问题,捕捞死亡率和资源量分别存在被低估和高估的现象。将来需要在模型结构设定、CPUE数据选择及模型参数的先验分布设置等方面进一步优化。     

利用微卫星分型技术对人工豢养瓶鼻海豚的父权鉴定

对国内豢养的瓶鼻海豚进行了血样采集,利用微卫星分型技术对相关个体进行了亲子鉴定。共采集到65头太平洋瓶鼻海豚和11头南瓶鼻海豚的血液样品,其中包括1头太平洋瓶鼻海豚和1头南瓶鼻海豚亲子鉴定所需的样本。通过8%聚丙烯酰胺凝胶电泳对物种特异性引物的扩增产物进行分型,得到了13对扩增稳定且多态性高的引物。Cervus软件的分析结果表明,有11对多态性引物适用于这两种海豚的亲子鉴定,并且成功鉴定出了两对父子关系。