Abstract:Distant-water fishery is a national strategic industry. China's distant-water fishery started at 1985, and after more than 30 years of development, it has now become one of the world's major distant-water fishery countries. Entering a new era, the development of China's distant-water fisheries is facing new situations and new tasks, and the state has made overall arrangements to promote the high-quality development (as HQD)of distant-water fisheries. Therefore, on the basis of summarizing and analyzing the current status and existing problems of China's distant-water fishery, this paper analyzes the industrial characteristics of distant-water fishery and the rich connotation of HQD to conceptualize the HQD of Chinese distant-water fishery and its industrial requirements. The results indicates that the HQD of distant-water fishery should develop three major industrial projects and establish three major guarantee systems. The three projects include modern ocean-going fishing fleets, quality control of fisheries products and comprehensive utilization with cold-chain systems, and zero-waste on fisheries production. While the three systems include the distant-water fisheries and environment monitoring system, the distant-water fishing and management monitoring system, and the global distant-water fisheries governance research institution. And suggestions and countermeasures for the HQD of China's distant-water fisheries are put forward from four aspects:industrial optimization, scientific and technological innovation, international fisheries governance, and institutional support system. This result of this study will be helpful to further understand and promote the HQD of China's distant-water fishery.

Abstract:Effective fisheries stock assessment and management is the key to achieving sustainable exploitation of fisheries resources. Traditional fisheries stock assessment and management is based on the assumption of stationarity, which considers key processes of population dynamics as time invariant. With increasing impact of climate change and human activities, these key processes may change over time, leading to non-stationary population dynamics and challenging the traditional assumption of stationarity. Based on the recently published research on this topic, we reviewed the mechanisms of non-stationary population dynamics and their impacts on fisheries stock assessment models, biological reference points and fisheries management. The results indicate that in the light of non-stationary population dynamics, both stock assessment models and biological reference points need to consider the temporal variation of key population processes, either by including environmental covariates or by time-varying model parameters, to deal with the impacts of non-stationary population dynamics on fisheries stock assessment and management. We suggest that resilience-based fisheries management is an important tool to cope with non-stationary population dynamics and maintain a stable and healthy fisheries social-ecological system.

Abstract:The Humboldt Current System (HCS) supports the largest pelagic fisheries in the world, and is also strongly affected by climate forces in the Eastern Boundary Currents System. In this study, the sea conditions of the HCS and status of its fishery were summarized, then the effects of marine environment and climate changes on growth and reproduction, population structure and resource fluctuation of four representative fishery species, Peruvian anchovy (Engraulis ringens), Chilean jack mackerel (Trachurus murphyi), Pacific sardine (Sardinops melanosticta) and Jumbo flying squid (Dosidicus gigas) were further discussed. This study suggested that the species abundance and distribution of the above four pelagic economic species are strongly influenced by seasonal, interannual and interdecadal climate changes and oceanic conditions of the HCS. Furthermore, research on the Humboldt current ecosystem(HCES) under the influence of future climate change is expected to be highly dependent on high-capacity comprehensive ecosystem models, considering physical environment, biochemical reaction, nutritional structure and other factors. Based on the models and their evaluations, a thorough understanding of the variations of various kinds of population in the HCES will facilitate a more reasonable development and scientific management of the fishery resources within such system.

Abstract:Argentinean shortfin squid, Illex argentinus, is one of the most important world fishery species characterized by semelparous reproduction, where the reproductive energy accumulation significantly links to the reproductive potential and the survivorship of hatchlings. To better understand the female's reproductive energy accumulation and the responsive relation to their living environments, we randomly sampled squid specimens from southwest Atlantic during 2019 and 2020, and applied the technique of tissue energy density determination to determine the energy density of reproductive tissues, namely ovary, oviducts and nidamental glands, and then to estimate the tissues' energy accumulation. We also applied the generalized additive mixed-effects models (GAMM) to investigate the relationships between reproductive tissues' energy density, energy accumulation and sea surface oceanic variables, namely sea surface temperature (SST) and chlorophyll a concentration (Chl.a). The results indicated that during the period of sexual maturation, the ovary energy density varied significantly, but both oviducts and nidamental glands did not show significant differences in the energy density with sexual maturation. In terms of energy accumulation, all of the three tissues showed an increasing trend till spawning. The energy density of ovary and nidamental glands was found in significant relation to SST, where the ovary energy density increased with increasing SST when SST was higher than 11 ℃, while the nidamental glands density declined with increasing SST. However, it was found that only ovary energy accumulation was significantly correlated with SST, declining with increasing SST. Regarding chlorophyll-a concentration, there were significantly positive correlations between ovary energy density, oviducts energy density and Chl.a, indicating positive effects of primary production on both tissues' energy density. Additionally, there were also significant effects of Chl.a on the energy accumulation of both ovary and nidamental glands. Cumulatively, the female Argentinean shortfin squid accumulated reproductive energy continuously till spawning, and the energy density and energy accumulation of the reproductive tissues were significantly correlated with SST and Chl.a, but the effects on the energy density and energy accumulation from the sea surface oceanic variables were likely to be tissue-specific.

Abstract:Illex argentinus is a short-lived cephalopod species, which is also a commercially important species in the world. The Malvinas Islands is one of the important fishing grounds for Illex argentinus. The abundance of Illex argentinus is highly susceptible to marine environmental changes and has large interannual fluctuations. According to the statistical data of Illex argentinus in the Malvinas Islands from 1995 to 2019, annual catch per fishing vessel (CPUE) was derived as an abundance index, and the gray catastrophe prediction GM(1,1) model was used to predict the future years of the Illex argentinus. The results showed that the upper years catastrophic year would occur in the years of 2021, 2028 and 2038 (CPUE ≥ 1615t per fishing vessel), and the lower catastrophe year would occur in the years of 2024, 2029 and 2036 (CPUE ≤ 784t per fishing vessel). Theoretically, the average relative error of the disaster model in rich years is 16.212%, the value of level deviation is 0.193, while the average relative error of the disaster model in poor years is 35.656%, and the value of level deviation is 0.199. The accuracy test for both models attain the level Ⅰ accuracy. According to the results, the grey catastrophe prediction model can simulate the years of abundance variation of Illex argentinus, and the prediction results can provide reference for the production and management of the species.

Abstract:Todarodes pacificus is a commercially important oceanic cephalopod resource, and its resource changes are vulnerable to the impact of the marine environment. In this study, the intrinsic natural growth rate (r) and the maximum environmental capacity (K) of the fluctuation parameters of the Todarodes pacificus population were combined with the sea surface temperature (SST) to construct four surplus production models respectively, which evaluated the changes in Todarodes pacificus population resources under the influence of SST. The research results showed that the resource evaluation model (model 2, model 3, and model 4) with environmental factors added to the four surplus production models had a deviation information criterion (DIC) value smaller than that of the traditional residual production model (model 1). The DIC value of the model 4 was the smallest (132.6), indicating that the model had the highest accuracy. According to the best model assessment, the fishing mortality F_t of Todarodes pacificus from 2007 to 2018 was lower than F_MSY. When MSY was 41.28×10⁴t, B_MSY reached 49.66×10⁴t, and there was a phenomenon of resource-based overfishing, but resources were gradually recovering. Studies have shown that the resource status of the winter population of Todarodes pacificus is greatly affected by the environment, so it is necessary to seriously consider the impact of environmental factors such as SST in future resource development and scientific management.

Abstract:Based on the survey data of swordtip squid (Uroteuthis edulis) collected by trawlers off the northern East China Sea from 2017 to 2020, we analyzed the biological characteristics of U.edulis, and studied the relationship between the growth characteristics of U. edulis and the environment by using generalized additive models (GAM). The results showed that during the four-year sampling period, the dominant dorsal mantle length and body weight groups of the U. edulis were 80-160mm and 10-170g for females respectively, with no significant differences (P>0.05); while the figures were 60-180mm and 10-170g for males respectively, with significant differences among years (P<0.01). Covariance analysis showed that there were significant differences in body weight-dorsal mantle length relationship in 2017 and 2020 (P<0.05), but no significant differences in 2018 and 2019 (P>0.05). The GAM showed that the M₉ model, in which dorsal mantle length interacted with sea temperature at 25m depth and year and seasonal factors were introduced, was the optimal model. Overall, males were more susceptible than females to external environmental influences on growth. The year has a greater impact on males, while the sea temperature at 25m depth has a greater impact on females. These results indicate that the growth of squid is closely related to environmental variation, with sea temperature being an important influence factor; and males have a more pronounced group of both sizes than females at 160mm dorsal mantle length, as a result of environmental variation and individual survival mechanisms. The biological characteristics of the squid and the influence of the environment on the squid will facilitate the management and conservation of fishery resources and provide a basis for the assessment of fishery resources.

Abstract:The main objective of the project was to evaluate the effectiveness of the seasonal moratorium on conservation of Jumbo Flying Squid (Dosidicus gigas) stock in the equatorial waters of Central Eastern Pacific. Based on catching data from December, 2016 to August, 2021, the spatial-temporal variations of catch effort, catch per unit effort (CPUE) and fishing ground gravity center were analyzed by using Grey correlation analysis and other methods. The results showed that:The average CPUE after the seasonal moratorium came to 6.34t/d, which was significantly higher than that before the moratorium (P<0.05). The grey correlation grades on longitude from 2017 to 2021 were 0.739, 0.761, 0.697, 0.721 and 0.892, respectively, and the grey correlation grades of latitude from 2017 to 2021 were 0.656, 0.799, 0.621, 0.721 and 0.803, respectively. The stock condition after the fishing moratorium was better than that before the fishing moratorium. The fishing ground gravity center after the fishing moratorium moved westwards significantly, which was different from that before the fishing moratorium. The fishing area with high production expanded from 114°W-118°W to 95°W-118°W. On the one hand, the fishing moratorium played a positive role on the conservation and sustainable use of the squid stock in the equatorial waters of Central Eastern Pacific. On the other hand, the study provided successful cases and practical experience for the fish stock management and scientific conservation of short life cycle species.

Abstract:Swordfish (Xiphias gladius) is a large swordfish species with high economic value, which is at the upper end of the food chain. It is important to assess its resources and develop management strategies for sustainable resource use and ecosystem conservation. In this study, we assessed the resource status of Indian Ocean swordfish based on the JABBA (Bayesian biomass assessment) and its extended version JABBA-Select, and compared and analyzed the effects of CPUE data and fishing selectivity on the assessment results. The results showed that when the data could satisfy the JABBA-Select model, the JABBA-Select model performed better than the JABBA model in stock assessment because it considers fishing selectivity and life history information. The Maximum Sustainable Yield (MSY) of the Indian Ocean swordfish resource in 2018 was estimated at 31 700 t, which was higher than the current catch of 30 100 t, with a 98% probability of being in a healthy state. The assessment results were less sensitive to the prior distribution of parameter r, and there was a negative correlation between the posterior distribution of parameter r and K. There was no significant retrospective problem in the proposed model. The projection analysis shows that the resource remains neither overfished nor overfishing until 2028 when the TAC is kept below 36 000 t.

Abstract:Estimation of bycatch of the blue shark (Prionace glauca,BSH), a major bycatch shark in the Pacific tuna longline fishery, is a current focus of stock assessment and management. Based on the data collected during the 2012-2018 survey in the Pacific Ocean by national observers of tuna longline fisheries, the relationship between the bycatch of BSH and spatiotemporal, environmental, and operational variables was analyzed using the Tweedie-GAM model. The performances of the model-based approach and the stratified ratio estimation method on bycatch estimation were compared using cross-validation. The results showed that the number of hooks per basket (HBF), longitude, and latitude were the most influential variables, and the cumulative deviance explained by the optimal model was 51.6%. The bycatch fluctuated and decreased with the increase of HBF, and decreased significantly when HBF was more than 19. The spatial distribution of bycatch showed significant latitudinal and longitudinal increasing patterns, as it was lower and uniformly distributed in low latitude areas (10°S-5°N), and higher in eastern areas than in western areas. Regarding the temporal distribution, we found that the seasonal difference of bycatch was not significant, but the bycatch of fishing sets operating on a full moon day increased significantly due to the influence of moonlight brightness. Also, relatively high chlorophyll concentration (≥ 0.15mg/m³) or worm waters (≥ 29.5℃) was associated with high bycatch. There was no significant linear relationship between the bycatch and the number of hooks per set. The results demonstrated that the model-based bycatch estimation method was superior to the stratified ratio estimation method. To reduce the bycatch of BSH, it is recommended that the HBF of longline fisheries in the Western and Central Pacific should not be less than 20. The number of fishing vessels operating in the mid-latitudes and waters east of 178°E should be controlled, and their implementation of bycatch mitigation measures should be monitored in a focused manner. To improve the accuracy of estimating the total bycatch of BSH or similar stocks, subsequent studies are suggested to adopt model-based estimation methods.

Abstract:The blue shark (Prionace glauca) is a main bycatch shark species in the tuna longline fishery. Based on the data of 778 blue sharks from 1272 fishing sets recorded by Chinese tuna longline observers in the Indian Ocean from 2012 to 2019, a generalized linear model (GLM) was applied to analyze the at-haulback mortality (i.e., the mortality rate when fish was captured and hauled back to the deck) and potential influencing factors of blue shark. The results were shown as follows:The overall at-haulback mortality of blue shark was 13.4%, and the at-haulback mortality of males was higher than that of females. Among the potential influencing variables, hook type, hook size, individual size, capture depth and capture latitude had significant influences on the survival status of blue sharks, and the impacts of hook type and capture latitude were the greatest. The interaction between hook type and latitude, as well as between gender and fork length also greatly contributed to at-haulback mortality. When using olecranon hooks, the more northerly being caught, the lower mortality rate was observed; for the other three hook types, the more northerly being caught, the higher mortality rate was observed. The larger the female blue shark was, the lower the mortality rate was observed; however, there was no clear pattern between the mortality rate of male blue shark and their individual size. This study can provide scientific information for reducing the estimated fishing mortality of blue shark and promoting the sustainable use of resources in this fishery.

Abstract:Chub mackerel (Scomber japonicus) is a pelagic economically important species and an important fishing target for Chinese coastal fisheries. The distribution of S. japonicus is significantly affected by climatic and environmental conditions at different scales. Based on the fisheries data of S. japonicus from July to September during 2005-2016 provided by National Data Center of Distant-water Fisheries of China, combined with the key environmental factor sea surface temperature (SST) data, this study quantified the temporal and spatial changes of fishing ground of S. japonicus on the analysis of determining the longitudinal and latitudinal gravity centers of fishing effort. Additionally, the distribution of the fishing ground in relation to longitude, latitude and SST was analyzed. Furthermore, the representative years were selected by cluster analysis to evaluate the impacts of abnormal climate events on the spatial and temporal distribution of SST and gravity centers of fishing ground for S. japonicus in the East China Sea. The results showed that there was significant interannual and monthly variation in gravity centers of fishing ground for S. japonicus in the East China Sea. The fishing ground gradually moved northeastward from July to September, which mainly occurred in the SST ranging from 25 to 28℃. Cluster analysis suggested that gravity centers of fishing ground in each month were divided into four categories, and significant difference was found between 2007 and 2015 in each month. Moreover, a statistically significant positive correlation was found between SST anomaly on the fishing ground of S. japonicus and oceanic Niño index. A La Niña event occurred in 2007 and an El Niño event occurred in 2015. When the La Niña event occurred, the SST on the fishing ground increased, and the gravity center of the fishing ground gradually moved northward; while if the El Niño event occurred, the SST on the fishing ground largely decreased, and the gravity centers of the fishing ground were mostly located in its southern waters. Our findings indicated that spatio-temporal distribution of S. japonicus in the East China Sea was strongly regulated by the impacts of the El Niño and La Niña-driven SST changes on the fishing ground.

Abstract:The mantis shrimp (Oratosquilla oratoria) is a benthic, megafaunal burrower and a predatory species. As an important commercial fishery species, its abundance is significantly correlated to sediment type. To understand the size at first maturity of female mantis shrimp widely distributed in Bohai Bay, the biological data, such as carapace length, kubo's standard length, total length, weight, gonadal development and ovarian weight, of female individuals were collected monthly from April to November except May in 2018 from research surveys on the board of fishing vessels. The determination of the immature and mature stages was performed based on the gonadal development, and then the size at first maturity was estimated using a logistic model with specific asymptote or variable asymptote. The results showed that:Female mantis shrimp could develop to maturity and complete reproduction at a standard length of 7.00-7.99 cm; Female individuals with 9.00-11.99 cm standard length made a great contribution to reproduction in quantities; There was a bias for estimates of the size at first sexual maturity between different sexual maturities judged by gonadal development, as well as models with different asymptotes; Estimates of size at first sexual maturity based on a logistic curve with variable asymptote were (9.42 ±0.02) cm, (10.44 ±0.04) cm and (12.03 ±0.17) cm respectively by using gonad stage of Ⅱ, Ⅲ and Ⅳ as criteria of mature for female mantis shrimp in Bohai Bay. And while the asymptote was assigned to 1 in the logistic model, the estimates of the size at first sexual maturity were (9.44 ±0.02) cm, (10.50 ±0.04) cm and (11.74 ±0.08) cm, respectively. This study enhanced our understanding of the relationships between the proportion of maturity and standard length of female mantis shrimp. While female mantis shrimp with gonadal development stages Ⅰ were treated as immature and individuals with gonadal development stages Ⅱ and above as mature, the size at first sexual maturity could be robustly estimated by using a logistic curve with variable asymptote through describing the relationship between the proportion of maturity and standard length. Based on these findings, it was suggested that the regional fishery should operate with a minimum legal size of 9.42 cm for mantis shrimp.

Abstract:In order to understand the length and weight characteristics of Conger myriaster in the coastal water of Shandong Province, this study analyzed the seasonal and spatial variations in the body length, weight and relative condition factors of C. myriaster based on bottom trawl surveys of fishery resources conducted in October, 2016 and January, May, and August, 2017. We used the linear mixed-effects model to illustrate the spatio-temporal heterogeneity in the relationships between body length and weight. The results showed that the average body length and weight were significantly smaller in winter than those in other seasons (P<0.05), and the relative condition factor in summer was significantly higher than that in other seasons (P<0.05). Linear mixed effect models revealed that seasons and areas significantly influenced the parameter a in length-weight relationships of C. myriaster. In the optimal model, the parameter b had a fixed value of 3.27 and the parameter a ranged from 4.78×10^-4 to 5.68×10^-4 among seasons and areas, with the largest value in summer, followed by autumn and winter, and the lowest in spring. Meanwhile, a had the largest value in area Ⅲ (depth>50 m), followed by area Ⅰ (depth<30 m) and area Ⅱ (30m

Abstract:To understand the age and growth of Pennahia argentata, 655 specimens of Pennahia argentata were collected from the offshore waters of southern Zhejiang. Age determination by sagitta otolith, and the growth function equation were fitted using Logistic, Gompertz and Von Bertalanffy growth function to analyze the structures and growth characteristics of the collected samples. It was found that:(1) Body length of samples ranged from 40 to 200 mm with a mean body length of (96.73±26.27) mm, and body weight varied from 0.8 g to 185.9 g with a mean body mass of (23.79±23.67) g; (2) The relationship between body length (L) and body mass (W) was not significantly different between males and females (P>0.05), and the function of body length-body mass was expressed as W=2×10^-5×L^3.0021 (R²=0.9800); (3) 157 otoliths were analyzed, and they aged between 0 and 4, age 0 being the dominant age group, accounting for 65.60%, while age 1 accounting for 18.47%, age 2 accounting for 6.37%, age 3 accounting for 7.64%, and age 4 accounting for only 1.91%; (4) Body length (L) and sagitta otolith short radius (S_R) was not significantly different between males and females (P>0.05), and the relationship was expressed as S_R=0.0108 L-0.310 6 (R²=0.8766); (5) Von Bertalanffy growth function seemed to be the most adequate model to describe growth based on the Akaike information criterion (AIC) test, with resulting growth parameters of L_∞=204.2 mm, K=0.4 per year and t₀=-1.56. The inflection point of the growth curve occurred at 1.19 years with a body length of 136 mm and body weight of 50.8 g.

Abstract:Chub mackerel (Scomber japonicus) in the East China Sea and Yellow Sea is one of the major commercial pelagic species in China, and its resource status and exploitation potential are receiving increasing attention. Strengthening the stock assessment research is the premise and foundation of the scientific management and sustainable utilization of chub mackerel. In this paper, a Bayesian biomass dynamics model was used to assess the chub mackerel. The catch data from 1979 to 2019 used in the assessment are from six provinces and two cities (i.e. Fujian, Zhejiang, Shanghai, Jiangsu, Shandong, Hebei, Tianjin and Liaoning) in China, Japan and Korea, and the resource abundance index data are from relevant references. Our results show that the prior distribution of intrinsic rate of increase (r) affects the parameter estimate of the model due to a strong negative correlation between r and carrying capacity (K) and a reasonable prior for r is helpful to improve the estimation quality of the model; the observation error precision of the catch data has an important impact on the estimates of the parameter and resource status; because the delineation of population structure of chub mackerel in the East China Sea and Yellow Sea is still controversial, it is currently not possible to separately evaluate each stock, and the stock assessment according to the statistical units is not conducive to the sustainable utilization of chub mackerel; chub mackerel has a high probability (>60%) of being overfished or being subject to overfishing; if the TAC (Total Allowable Catch) is below 4.82×10⁵ t, the probability of the stock not being overfished and not undergoing overfishing is expected to be greater than 60% in 10 years. Due to the current controversial status of the population classification of chub mackerel in the East China Sea and Yellow Sea and the difficulties in collecting corresponding data, we suggest that the stocks in the East China Sea and Yellow Sea be treated as one stock to meet the basic assumptions of the stock assessment model and to improve the quality of stock assessment. It will be beneficial to the sustainable utilization of chub mackerel if the catch is below 4.82×10⁵ t.

Abstract:The biomass of marine fishery resources fluctuates in time. Understanding the features of biomass fluctuations at different time scales can provide a perspective in investigating the impacts of relevant factors on biomass variations. Based on the anchoveta (Engraulis ringens) biomass time series from 1985 to 2021, this study used Complete Empirical Mode Decomposition with Adaptive Noise (CEENDAN) to extract anchoveta biomass fluctuations features at different time scales and evaluated their contributions to overall time series. Besides, the results were evaluated with El-Niño and La-Niña events under cross-correlation analysis because these events greatly related with the variations in anchoveta biomass according to previous studies. Results showed the CEEMDAN could decompose the anchoveta biomass time series into five Intrinsic Mode Function (IMF_i) and one residual (RES). Anchoveta biomass fluctuations were mainly under the control of its seasonal, annual (IMF₁) and inter decadal (RES) variations. RES was found to be associated with the regime shift in Humboldt Current ecosystem at Southeast Pacific Ocean. Cross-correlation analysis revealed El-Niño and La-Niña events could impact the anchoveta biomass fluctuations mainly at annual and inter annual scale. Sea surface temperature anomaly at Niño1+2 region (Niño1+2 index) was believed to play a more obvious role in tracking the anchoveta biomass fluctuations than Oceanic Niño Index. Higher values of the Niño1+2 index within 1.0-1.5 years might have a negative impact on the anchoveta biomass.

Abstract:In order to explore the effects of drag and configuration for twine diameter and catch on the trawl codend, different codend models with three twine diameters (1.11 mm, 0.96 mm, 0.54 mm) and two catch status (empty codends and codends with catch)under five current speeds (0.5 m/s, 0.6 m/s, 0.7 m/s, 0.8 m/s, 0.9 m/s) were carried outfor model test to compare and analyze the changes of configuration, drag and the horizontal hanging ratio of codends in the flume tank of Shanghai Ocean University. The results show that:(1) For empty codends, the drag coefficient of codend increases with the increase of twine diameter. With the increase of Reynold number, the drag coefficient decreases. (2) There is a positive correlation between codend resistance and flow velocity, twine diameter and catch. (3) The middle width of codend with catch increases with the increase of twine diameter. Compared with empty codends, the length of codends with catch increases obviously with the increase of flow velocity. While the overall configuration of empty codends is full. (4) The horizontal hanging ratio of empty codends decreases first and then tends to be stable, while the horizontal hanging ratio of codends with catch decreases first and then increases to the maximum. The results of this study can provide scientific basis for improving the hydrodynamic performance of mid-water trawl codend and the operation characteristics and selectivity of fishing gear.

Abstract:To investigate the effects of light color, power, depth of LED underwater fishing lamp and seawater chlorophyll concentration on its light field distribution, a new underwater light transmission model was established based on Monte Carlo algorithm. The underwater light field distribution under different conditions was calculated by using the control variable method and the relative effective illumination range (REIR). The ratio of the area surrounded by the 0.1-10.0 lx isoline to the computational domain was taken as an evaluation index. With REIR for index, light filed distribution under the combined condition of was analyzed. The results showed that:(1) Under the same light power, the lights with REIR from high to low were green light, white light and blue light, and when the light power was 420 W and the seawater chlorophyll concentration was 0.1 mg/m³, the ratio of REIR values of the three light colors was 1.58:1.31:1; (2) Under the same light color, when the seawater chlorophyll concentration was 0.1 mg/m³, the power of fishing lamp increased from 420 W to 1200 W, and the REIR value of blue, green, and white light lamp increased from 31.68%, 50.27% and 41.78% to 38.59%, 56.91% and 50.15% respectively; while the power of lamps increased nearly three times, the increase of REIR was limited; (3) As the depth of lamp increased, the REIR of lamps increased at first and then kept stable. The maximum value of green and white lamp was about 9.69%-9.84% when the depth of lamp reached 20 m under water, while the maximum value of blue lamp was about 5.60% when the depth of lamp reached 15 m under water; (4) As the chlorophyll concentration increased from 0.1 mg/m³ to 5.0 mg/m³, the REIR value of green, white and blue lamp decreased from 31.89%, 48.25% and 42.05% to 1.65%, 2.09% and 2.22% respectively. The results can be helpful for the selection of light color and power, the depth of underwater lamp, and the estimation of effective illumination range of lamp.

Abstract:In order to explore the difference of phototactic behaviors of zebrafish under different light conditions, the behavior responses of 6-month-old adult zebrafish under ultraviolet light and visible light were recorded, and the distribution of zebrafish under five monochromatic lights (purple, blue, green, yellow and red) and dark condition were also recorded. The results showed that when the stimulus light was UV, zebrafish preferred to swim to the dark side, and when the stimulus light was visible light, zebrafish preferred to swim to the visible light side. When UV and visible light were set in test area A and test area B respectively, the preference index of zebrafish did not increase with the increase of UV stimulation intensity, while when UV and visible light were set in test area B at the same time, the preference index of zebrafish showed a significant downward trend with the increase of UV stimulation intensity. The average distribution rate of zebrafish in red light in 5min and 30min was higher than that in purple light, in blue light, and in yellow light by sequence. The average distribution rate of green light in 5min was higher than that in red light, and the average distribution rate of green light in 30min was higher than that in blue light and lower than that in purple light. The results revealed that zebrafish tended to visible light and stayed away from ultraviolet light, showing obvious UV avoidance and phototaxis, and there was a significant inhibiting effect between UV avoidance and phototaxis, but there was no synergist between them. In addition, zebrafish had a higher preference for red light, green light and purple light, but lower preference for yellow light. The results can provide reference for the research of visual ecology of zebrafish.

Abstract:In order to understand the effect of escape opening type on the escaping behavior of Portunus trituberculatus in crab pots, the response behavior of crabs pre-stocked in pots to rigid rectangular escape vent with 40 mm height×200 mm width and meshes escape openings composed of two 40 mm×60 mm meshes in lower position and one 60 mm×60 mm mesh in higher position was observed and recorded in tank by infrared underwater camera. Both escape opening were located at the bottom edge of side panels. According to behavioral characteristics of crab behaviors, the continuous response behavior of P. trituberculatus to pots and escape openings was divided into four stages:search, detect and approach, attempt to pass, and pass through the escape openings. The video recording of the response behavior showed that, compared with those in the experimental pot with rigid rectangular escape opening, pre-stocked P. trituberculatus in pot with meshes escape opening explored more frequently and persistently. Crabs could locate, detect and approach the escape opening readily in their search behavior at the floor of pots, regardless of type of escape opening. However, the average number of times and duration of approaching the meshes escape openings were greater than those of approaching the escape rigid escape vent (P< 0.001 for average duration and P=0.061 for average number of times). For crabs approaching openings, nearly 85% of them attempted to pass through openings and no significant difference in attempt to pass through between different opening types was detected. Duration of stay in front of the escape openings of P. trituberculatus, which was considered as a significant factor influencing the attempt to pass thorough, was significantly longer (P=0.006) for meshes escape openings than that for rigid rectangular escape vent. All crabs walked sideways through escape openings, so whether crabs could pass through an rigid escape vent depended upon the relationship between carapace depth and opening height of rigid escape vent. As for the meshes escape openings, crabs preferred to pass through the lower opening and eventually succeeded in escaping. Nevertheless, the effective releasing crabs of meshes escape openings suggested that the mesh opening could be used as an effective escape device and the usage of biodegradable netting panel would be one of the technical measures to alleviate ghost fishing effect when pots were lost in crab pot fisheries.

Abstract:Marine fishery resources are important animal protein sources for human beings, the rational exploitation of which is of great significance. Based on the catch data of 19 global fishing areas from 1990 to 2019, this paper studied the relationship between the catch and total catch of each fishing areas, and among catches of each fishing areas by using grey correlation clustering, and the main species types that affect catches in the same fishing areas were identified. The results showed that there was a strong correlation between the catch in most fishing areas and the total catch of global seas, and there were 16 fishing areas with a grey correlation degree greater than 0.900. With the exception of the Antarctic Atlantic, Antarctic Pacific and Arctic Sea, the other fishing areas are correlated with each other by more than 0.900. The critical value r=0.975 of the associated clustering matrix was set as the classification basis, and the groups Ⅰ and Ⅱ with obvious classification were obtained. GroupⅠ includes Northwest Pacific, Northeast Atlantic, Northeast Pacific, Southeast Atlantic, Western Central Atlantic, Mediterranean and Black Sea, and the catch trends of the six fishing areas all fluctuated within a certain range; Group Ⅱ includes Western Central Pacific, Eastern Indian Ocean, Eastern Central Atlantic, and Western Indian Ocean, the catch of which showed a steady increase trend. Pelagic marine fish and demersal marine fish had the highest grey correlation with the total catch of the two groups. Our findings suggested that the grey theory system can be used to scientifically evaluate the exploitation status of marine fishery resources in various fishing areas of the world, and the evaluation results can provide reference for the sustainable development of global marine fishery.

Abstract:The West Indian Ocean is an important area of marine fishing, and the analysis of the species composition and catch of fishing countries and regions provides the basis for evaluating the utilization status of fishery resources, and also an important support for ensuring the sustainable development and scientific management of fishery resources. Based on the catch data of the Western Indian Ocean from 1950 to 2019 provided by FAO, the species and catch composition of the main fishing parties in the past 70 years were analyzed by using dominance analysis, and the contribution rates of main fishing parties and species to total catch were compared under different time series. The results showed that the total catch in the Western Indian Ocean was on the rise, which could be divided into three periods:1950-1982, 1983-2005 and 2006-2019. The results showed that there was no significant difference among the first 10 species and fishing parties in the cumulative catch of each stage. The cumulative catch of Sardinella longiceps was the highest, and the contribution rate of skipjack and Yellowfin tuna to total catch was relatively high. India, Pakistan and Iran had the highest amount of catch in all stages in the coastal states and regions, while Spain, France, Japan and Taiwan Province were the non-coastal countries and regions with the highest catch, which contributed to more than 10% to the total catch in the Western Indian Ocean at each stage. The research suggests that based on the current status and potential of fishery resources exploitation in the Western Indian Ocean, the major fishing countries and regions should reduce their fishing effort and conserve the over-exploited economic species, and increase the exploitation of short life cycle species with rich resources, in order to ensure the sustainable use of fishery resources in the Western Indian Ocean.