Net Mesh Research Articles

Phytoplankton Species in Linkage to Water Quality and Landsat Data Indices at the Southern Part of Burullus Lake, Egypt

In aquatic ecosystems, phytoplankton assemblages are mostly affected by different water quality parameters. In March 2020, water and phytoplankton samples were collected from seven geo-referenced stations distributed along the southern part of Lake Burullus, in front of drains. Physio-chemical parameters (temperature T°C, pH, dissolved oxygen DO, Salinity, nitrite NO2 , phosphate PO4 , ammonia NH4 , and silicates SiO4 ) were analyzed in water samples. Phytoplankton samples were collected using a net mesh of a size of 20 µm. The most abundant classes are Chlorophyceae, Cyanophyceae, and Euglenophyceae in stations 7, 2, and 6, respectively. The difference between classes and species is based on the different discharge of wastes, the high load of organic matter, and salinity. Results of the average water quality index AWQI showed low water quality in front of drainage waters. The vegetative cover increases on the eastern side. Landsat images were acquired, treated, and processed for concluding three important indices along with the three sectors of the lake. These indices are normalized difference vegetation index (NDVI), normalized difference water index (NDWI), and phytoplankton turbidity index (PTI). The NDVI showed that the vegetation-covered areas of about 11.3, 2.6, and 1.36 km2 , and NDWI showed water areas of about 105.09, 153.25, and 43.57 km2 for eastern, middle, and western parts, respectively. PTI indicated that nearly 55.3% of phytoplankton turbidities concentrated towards the western side of the lake, followed by 44.21% at the middle part and 25.14 % on the eastern side. It is concluded that water quality nearby drains are bad, where the phytoplankton turbidities as observed from Landsat images were increased towards the southwestern parts.

Length‐weight relationships of fish species from the Stung Russei Chrum River basin, Kingdom of Cambodia

This study evaluated the length-weight relationships (LWRs) for three teleost fish species sampled from the Stung Russei Chrum River basin, Kingdom of Cambodia. The fish were collected during two dry seasons (April 2019 and November 2019) and one rainy season (October 2018) using monofilament trammel nets (2–12 cm mesh size), cast net (mesh size 2 cm) and scoop-nets (mesh size with 0.3 cm). Results showed that all fitted regressions were highly significant and the coefficients of determination (r2) were high. This study expanded the value of maximum total length for Cyclocheilichthys apogon and Poropuntius laoensis while reported the wider ranges of total mass for Poropuntius laoensis. Moreover, our present study also provided the novel LWRs records for Hemibagrus filamemtus.

ESTIMATION OF GROWTH, MORTALITY, AND EXPLOITATION STATUS OF NURSE TETRA (Brycinus nurse) AND TRUE BIG SCALE TETRA (Brycinus macrolepidotus) (FAMILY: ALESTIDAE) FROM THE NEW CALABAR RIVER, NIGERIA

This study aimed to determine the growth patterns, mortality, and exploitation status of two species of Alestidae in the New Calabar River, Nigeria. For this purpose, fish samples were collected monthly from three landing sites from the local fishermen using gill nets (mesh sizes: 15-25mm), beach seine (mesh sizes: 2.3-10mm), and cast nets (mesh sizes: 15 -25mm). The length-weight relationship revealed exponent “b” value for Brycinus nurse was 3.54 and 3.21 for Brycinus macrolepidotus while the condition factors were 1.08 and 1.02 for Brycinus nurse and Brycinus macrolepidotus respectively. The growth parameters of Brycinus nurse asymptotic length (L) and growth coefficient (K) were 24.46 cm and 0.52 yr-1, respectively, while those for Brycinus macrolepidotus L was 28.88 cm and K was 0.22 yr-1. The reproductive load (L50/L) ratio was found to be 0.59 and 0.61 for B. nurse and B. macrolepidotus, respectively. Exploitation rate (E) for B. nurse was 0.26 and 0.11 for B. macrolepidotus while length-at-first capture (Lc) was 14.49 cm for B. nurse and 17.64 cm for B. macrolepidotus. The natural mortality was greater than the fishing mortality for both species and Logistic regression of the probability of capture routine values recorded for B. nurse were higher than that of B. macrolepidotus. Maximum exploitation rate (Emax) was less than 0.5 for both B. nurse (0.41) and B. macrolepidotus (0.42). These values were close to the maximum allowable limit; therefore, the species may be unsustainable when fishery intensifies in the future. To ensure sustainable exploitation of the two Alestid species in the area, fishing effort should be regulated.

Surviving a Reclamation Project: Shifting Fisherfolk Provisioning Strategies in a Metropolitan City

Development has often been equated with modernization and urbanization, as reflected in government development programs such as the Cebu Integrated Area Development Master Plan (CIADMP). One of the flagship projects under the CIADMP is the 330.9-hectare Cebu South Reclamation Project (CSRP) formulated by foreign consultants, local government authorities, and the business sector. Underlying these indicators of economic development that encourage such projects, urban fishing communities have been uprooted from their livelihoods that are reliant on the sea subsequently reclaimed by the project. This study focuses on how the affected fisherfolk in Cebu City changed their household provisioning strategies as a result of the CSRP. The study primarily utilized ethnographic research methodologies, including key informant interviews, focus group discussions, deep hanging out, and field observation. Newspaper research and secondary data analysis were likewise done to supplement field data. Findings are based on the narratives of the affected residents, which show that prior to the CSRP, primary livelihood strategies of most residents revolved around small-scale fishing practices: panawom (diving/spear fishing), pamasol (hook and line fishing), pamukot (fishing using mesh nets), panginhas (gleaning), and panu (gathering shrimps and crabs at low tide). The implementation of the CSRP has adversely affected their livelihood, leading them to shift to less lucrative and mostly informal, irregular, temporary service-related work. Strategies employed were not only in terms of livelihood options but also in tapping social networks, pooling resources, cutting on consumption costs, and joining resistance movements.

Biochemical, Physiological, and Productive Response of Greenhouse Vegetables to Suboptimal Growth Environment Induced by Insect Nets.

Simple SummaryGlobal warming jeopardizes agriculture, which must satisfy the demands of the world’s expanding population for both staple and high-quality products while ensuring increased sustainability. Environmental and regulatory pressure has prompted farmers to convert their production strategies towards sustainable agriculture systems, by introducing for instance, integrated pest management strategies. Insect nets are a suitable tool for pest control but require careful assessment of their effects on the generated microclimate. The low porosity, mandatory for proper exclusion, results in suboptimal airflow and in temperature rise with detrimental effects on crop production and quality. The biochemical and morpho-physiological changes induced by high-temperature impact vegetable crop performance and product quality in advanced growing systems, and also represent a challenge for the most impoverished developing countries of the world, which rely on local horticultural products as a key source of dietary diversity.Environmental pressure poses a major challenge to the agricultural sector, which requires the development of cultivation techniques that can effectively reduce the impact of abiotic stress affecting crop yield and quality (e.g., thermal stress, wind, and hail) and of biotic factors, such as insect pests. The increased consumer interest in premium-quality vegetables requires the implementation of sustainable integrated pest management (IPM) strategies towards an ever-increasing insect pressure, also boosted by cultivation under protected structures. In this respect, insect nets represent an excellent, eco-friendly solution. This review aims to provide an integrative investigation of the effects of the insect screens in agriculture. Attention is dedicated to the impact on growth, yield, and quality of vegetables, focusing on the physiological and biochemical mechanisms of response to heat stress induced by insect screens. The performance of insect nets depends on many factors—foremost, on the screen mesh, with finer mesh being more effective as a barrier. However, finer mesh nets impose high-pressure drops and restrict airflow by reducing ventilation, which can result in a detrimental effect on crop growth and yield due to high temperatures. The predicted outcomes are wide ranging, because heat stress can impact (i) plant morpho-physiological attributes; (ii) biochemical and molecular properties through changes in the primary and secondary metabolisms; (iii) enzymatic activity, chloroplast proteins, and photosynthetic and respiratory processes; (iv) flowering and fruit settings; (v) the accumulation of reactive oxygen species (ROSs); and (vi) the biosynthesis of secondary biomolecules endowed with antioxidant capacity.

Growth parameters of invasive gibel carpCarassius gibelio(Bloch, 1782) in Lake Marmara (Turkey)

AbstractThe objective of this study was to determine growth parameters, such as age–length and length–weight relationships, as well as condition factors and sex ratio, of theCarassius gibelio(Bloch, 1782) population in Lake Marmara (western region of Turkey), which is one of the most important fishing areas. Fish were caught on a monthly basis by gillnets and trammel nets (mesh size 10–50 mm) between March 2012 and February 2013. A total of 1058 specimens (809 females and 249 males) were examined. The female–male ratio was 1:0.31. The maximum age was determined as VI and V for females and males, respectively. The total length of females and males ranged from 10.0 to 27.5 cm and from 10.2 to 24.0 cm, respectively. Their weight varied from 17.1 to 378.4 g and from 17.7 to 244.9 g, respectively. Length–weight relationship parameters werea= 0.014 andb= 3.040 for females anda= 0.015 andb= 3.039 for males. Von Bertalanffy growth parameters of theC. gibeliopopulation were as follows: L∞= 35.86 cm, k = 0.189 year−1, t0= −1.238 years. Minimum and maximum condition factors were 1.56 for females in October and 1.82 in May and 1.67 for males in September and 1.94 in January.

Biometric indices of five miniature fish from the catchment area of Kaptai Lake, Bangladesh

The present study reports on biometric indices comprising length-weight relationships (LWRs) of five miniature freshwater fish species from the Kaptai Lake, the largest lake in the People's Republic of Bangladesh. The study area included 3 stations in the 11,122 km2 catchment area of the lake and each station was sampled from November 2017 to April 2018 using push net (mesh size 2 mm) for capturing the species. The values of growth coefficient b of the LWRs (W = aTLb) of the species Oryzias dancena, Oryzias melastigma, Gobiopterus chuno, Brachygobius nunus and Badis chittagongis were 2.9575, 3.1467, 3.0535, 3.058 and 2.9396 with above 0.95 coefficient of correlation (r2). These results represent the first study of LWRs for these fish species which may help in management and conservation of the species in the whole country, including its geographical distribution.

Sown wildflower fields are an efficient measure to reduce visitation rates of honeybees and other pollinating insects on Jacobaea vulgaris

Local mass occurrences of Tansy ragwort (Jacobaea vulgaris, Asteraceae), a native plant usually sparsely interspersed within extensive grassland, have been suggested to cause health hazards for livestock and humans. While current management options, particularly herbicide application and mechanical eradication, undermine conservation targets of extensive grasslands, sown wildflowers are a popular agri-environment scheme that may reduce pollinator visitation on J. vulgaris and thus, mitigate the plant’s dominance. Hence, with this study we aimed to explore whether the availability of sown wildflower patches reduces pollinator visitation rates on J. vulgaris in species-rich and species-poor grassland, respectively, and whether patterns depend on wildflower cover. To do so, we monitored pollinator visitation rates on J. vulgaris when wildflower fields were available to flower visitors or temporarily covered by mesh nets in a field experiment. The availability of wildflower patches significantly reduced visitation rates of honeybees, bumblebees, solitary bees and hoverflies on J. vulgaris, while increasing wildflower cover promoted this effect for J. vulgaris in species-poor grassland. Moreover, species-specific flower preferences and seasonal shifts in the quantitative availability of wildflower species determined the efficacy of wildflower patches. To conclude, our findings suggest sown wildflower fields as an alternative management option to mitigate the dominance of J. vulgaris in plant-pollinator networks given that wildflower mixtures are tailored to species-specific requirements of flower visitors. Future research, however, should explore whether wildflower fields ultimately mitigate the negative consequences associated with the local mass occurrences of J. vulgaris without undermining conservation targets on extensive grassland.

Plankton net mesh size influences the resultant diversity and abundance estimates of copepods in tropical oligotrophic ecosystems

Quantitative assessment of planktonic organisms is a key issue in understanding biodiversity, biomass, and carbon fluxes in marine ecosystems during the ongoing Anthropocene. However, the implications of the choice of plankton sampling equipment in tropical marine ecosystems have not been fully addressed. The goal of this study was to investigate the abundance and diversity of copepods derived from two different mesh sizes, 120 and 300 μm, to determine differences that may change our perception of the actual role of the key planktonic organisms in tropical marine ecosystems, due to the fact that missing information may be a real problem in trophic estimations (e.g. benthic-pelagic coupling processes in coastal areas). Samples were collected along 650 km of coastline in the Equatorial Atlantic. The average abundance of copepods calculated using the 120 μm net was five times higher than that of the 300 μm net. However, species richness was higher when using the 300 μm net compared to that of the 120 μm. Using the 300 μm net, the number of exclusive taxa (not found in the 120 μm mesh sampling) was higher. The Venn diagram showed that 10% of the copepod taxa were recorded exclusively in 120 μm net, whereas only 30% occurred in the 300 μm net. To improve our understanding of the structure and functioning of tropical marine ecosystems, plankton nets with smaller mesh openings should always be used to estimate abundance because of the dominance of small organisms in the nutrient-poor food webs, giving a new perspective on the available energy in water column and benthic processes of suspension feeding organisms. The absence of these smaller nets will produce an inaccurate picture of the plankton communities and their contributions to other trophic levels, including the blue carbon budget estimates worldwide.

Riverine plastic pollution from fisheries: Insights from the Ganges River system

Abandoned, lost or otherwise discarded fishing gear represents a substantial proportion of global marine plastic pollution and can cause significant environmental and socio-economic impacts. Yet little is known about its presence in, and implications for, freshwater ecosystems or its downstream contribution to plastic pollution in the ocean. This study documents fishing gear-related debris in one of the world's largest plastic pollution contributing river catchments, the Ganges. Riverbank surveys conducted along the length of the river, from the coast in Bangladesh to the Himalaya in India, show that derelict fishing gear density increases with proximity to the sea. Fishing nets were the main gear type by volume and all samples examined for polymer type were plastic. Illegal gear types and restricted net mesh sizes were also recorded. Socio-economic surveys of fisher communities explored the behavioural drivers of plastic waste input from one of the world's largest inland fisheries and revealed short gear lifespans and high turnover rates, lack of appropriate end-of-life gear disposal methods and ineffective fisheries regulations. A biodiversity threat assessment identified the air-breathing aquatic vertebrate species most at risk of entanglement in, and impacts from, derelict fishing gear; namely species of threatened freshwater turtle and otter, and the endangered Ganges river dolphin. This research demonstrates a need for targeted and practical interventions to limit the input of fisheries-related plastic pollution to this major river system and ultimately, the global ocean. The approach used in this study could be replicated to examine the inputs, socio-economic drivers and ecological impacts of this previously uncharacterised but important source of plastic pollution in other major rivers worldwide.

Examination of net volume reduction of gravity-type open-net fish cages under sea currents

Owing to heavy criticisms of nearshore fish farming for causing environmental pollution and encroaching on sea space used for shipping, boating, recreational sea activities and marine eco-tourism, offshore fish farming has now being seriously considered. Moreover an offshore site provides more pristine water and greater space for increased fish production. However, offshore fish farming poses challenges such as a more energetic sea environment. A higher sea current can lead to large deformation of fish net and hence a net volume reduction which compromises fish welfare. With the view to identifying the effects of various important parameters on net volume reduction of a gravity-type open-net fish cage, this paper adopts a mass-spring model for the dynamic analysis of current-induced net deformations of cylindrical fish nets with discrete weights hanging at the bottom edge of the nets. In this model, the net mesh comprises knot nodes and bar nodes connected by tension-only massless springs. The spring stiffness is determined from the net bar diameters and material properties. The current-induced loads are applied to each node and calculated based on Morrison’s equation. The governing equation system for nodal motions can be established according to Newton’s second law, and solved by using the Runge-Kutta method for the real-time net deformations. The effects of net string reinforcements, weight distributions and net shapes on the net volume reduction are studied with the view to shed insights into how one may improve fish cage designs to effectively mitigate net deformation under high sea current speeds in offshore fish farming sites.

Development of an Efficient Processing System for Young Coconut Husk

A processing system for young coconut husk was developed to cater abandoned young coconut husk in the coconut industry. This was a new invention as an alternative to the current old coconut husk extractor in the coconut industry. There were several machines developed; 1) chopping machine, 2) young coconut husk extractor, 3) conveyor system, and 4) rotary screener. This processing system was introduced to ensure the abandoned young coconut husk can be extracted into fiber and cocopeat. The evaluation results showed that the average machine capacity of the young coconut husk extractor was 350.79 kg/hour with the average weight ratio of unfiltered cocopeat and fiber produced at 70 % and 30 % respectively. The assessment of quality for fiber and cocopeat was done by using rotary screener that equipped with 16 mesh nets. The result of cocopeat was 2.8 % in the extracted fiber after extraction and filtration. Based on the analysis, cost of operation was RM 3.80/hr or equal to RM 668.70/month for the entire processing system. Total monthly income for machines owner was RM52,923.30 and the ROI was 88.21%. The results showed that the processing system was able to process the abandoned young coconut husk into fiber and cocopeat. Performance evaluation of each machine should be carried out in the future research to identify machines efficiency and durability.

Zooplankton filtering efficiency of the baleen of a North Atlantic right whale, Eubalaena glacialis

In order to define the trophic requirements of the North Atlantic right whale, a series of experiments were designed to examine the foodcapture characteristics of the species. The food filtering efficiency of the baleen of an immature right whale was tested in a flume usinggraded samples of zooplankton, primarily calanoid copepods, collected in the path of surface-feeding whales. The filtering capacitydecreased with decreasing prey organism size, so that greater than 95% of the available caloric content of the zooplankton samples wascaptured in size fractions collected on 333m mesh nets. The experiments demonstrate that the filtering efficiency of the baleen narrowlyfocuses the right whale’s feeding on an energy-rich, yet spatially and temporally variable, portion of the mid-water food resource

Quantitative and qualitative evaluation of plastic particles in surface waters of the Western Black Sea.

Microplastic abundances have been studied intensively in the last years in marine and freshwater environments worldwide. Though several articles have been published about the Mediterranean Sea, only few studies about the Black Sea exist. The Black Sea drains into the Mediterranean Sea and may therefore significantly contribute to the Mediterranean marine pollution. So far, only very few articles have been published about micro-, meso- and macroplastic abundances in the Western Black Sea. In order to fill this knowledge gap and to decipher the number of plastics on the water surface, 12 samples were collected from surface waters with a neustonic net (mesh size 200μm) in the Black Sea close to the Danube Delta and the Romanian shore. Organic matter was digested and plastic particles were isolated by density separation. The results of visual inspection, pyrolysis GC-MS (for microplastics) and ATR-FTIR (for mesoplastics >5mm) revealed an average concentration of 7 plastic particles/m³, dominated by fibers (∼76%), followed by foils (∼13%) and fragments (∼11%). Only very few spherules were detected. The polymers polypropylene (PP) and polyethylene (PE) dominated which is in line with other studies analyzing surface waters from rivers in Western Europe as well as in China. Statistical analyses show that the plastic concentration close to the mouth of the Danube River was significantly higher than at four nearshore regions along the Romanian and Bulgarian coastline. This could be explained by plastic inputs from the Danube River into the western part of the Black Sea.

Length–weight relationships of four fish species from Vembanad‐Kole Wetland (Kerala, India)

The length–weight relationships (LWRs) of four fish species were determined from Vembanad-Kole Wetland, Kerala, India between June 2015 and May 2016. Fish samples were collected monthly from various fishing gears such as gill nets (50 m long and 1.5 m height, mesh sizes 30–100 mm, soaking time 8 hr) and seine nets (mesh sizes 8–16 mm). Values of the parameter b ranged from 2.896 to 3.165 and such values are within the expected range. This study reports the new maximum total length for Channa pseudomarulius and Hyporhamphus xanthopterus.

Health risk indices and zooplankton-based assessment of a tropical rainforest river contaminated with iron, lead, cadmium, and chromium

Oil exploration’s devastation on health and the environment may far outweigh its economic benefits. An oil spill occurred at Egbokodo River in Delta State, Nigeria, thereby polluting the land and water bodies. The study was therefore aimed at evaluating the impacts of iron, lead, cadmium, and chromium on the zooplankton community structure of Egbokodo River and the potential health risks. Zooplankton and surface water samples were collected to investigate the concentrations of trace metals and zooplankton abundance. The associated carcinogenic and non-carcinogenic effects of the metals in the water were analyzed. Trace metal concentrations in the surface water were determined using atomic absorption spectroscopy (Philips model PU 9100) and zooplankton samples were collected using a hydrobios plankton net (mesh size 25 µm). Total petroleum hydrocarbons (TPH) and oil and grease (OG) were determined using Agilent 7890B gas chromatography coupled to flame ionization detector (GC-FID) and volumetric analysis respectively. The trend of the abundance of zooplanktons cross the river was 18 individuals (Station A) < 100 individuals (Station B) < 155 individuals (Station C). Cyclopoida proved to be the most resilient to the impacts of the oil spill. On a taxa basis, the order of abundance among Calanoida, Cyclopoida, Cladoceran, and Harpacticoida was Station C > Station B > Station A, except in Amphipoda where Station B > Station C > Station A was observed. Iron and lead posed significant carcinogenic risks that are liable to be inflicted by the ingestion of the water. The cumulative non-carcinogenic health risk in the male was the only significant (> 1) among the age groups. Total petroleum hydrocarbons (TPH), oil and grease (OG), iron, and lead had notable impacts on the general abundance of zooplankton in the aquatic habitat. The dominance of the Cyclopoida in the river buttressed the impact of the oil spill which warrants a prompt remediation measure. The pollution had notable ecological impacts on the zooplankton community structure of the aquatic habitat. The adults in the nearby human populations are liable to elicit carcinogenic health challenges associated with lead and iron ingestion. The males are at risk of non-carcinogenic illnesses which are associated with the combined toxicity effects of all the metals. The study suggests that the pollution in Egbokodo River was validated by the dominance of the Cyclopoida in the aquatic habitat. The study confers bioindicator reputation on the Cyclopoida for future biomonitoring studies.

Harps under Heavy Fog Conditions: Superior to Meshes but Prone to Tangling.

In arid yet foggy regions, fog harvesting is emerging as a promising approach to combat water scarcity. The mesh netting used by current fog harvesters suffers from inefficient drainage, which severely constrains the water collection efficiency. Recently, it was demonstrated that fog harps can significantly enhance water harvesting as the vertical wire array does not obstruct the drainage pathway. However, fabrication limitations resulted in a very low shade coefficient of 18% for the initial fog harp prototype and the field testing was geographically confined to light fog conditions. Here, we use wire-electrical discharge machining (wire-EDM) to machine ultrafine comb arrays; winding the harp wire along a comb-embedded reinforced frame enabled a shade coefficient of 50%. To field test under heavy fog conditions, we placed the harvesters on a closed-circuit test road and inundated them with fog produced by an array of overlying fog towers. On average, the fog harps collected about three times more water than the mesh netting. During fog harvesting, the harp wires were observed to tangle together due to the surface tension of water. We developed a rational model to predict the extent of the tangling problem for any given fog harp design. By designing next-generation fog harps to be anti-tangling, we expect that even larger performance multipliers will be possible compared to the current mesh harvesters.

Spatial and temporal variability of the zooplankton community at Araruama Lagoon

Em ambientes hipersalinos a comunidade zooplanctônica geralmente é pobre em densidade e riqueza, mesmo assim esses organismos são fundamentais para a base da cadeia alimentar local. O presente estudo tem como objetivo avaliar a variação espacial e temporal da comunidade zooplanctônica da Lagoa de Araruama, considerando os dados abióticos de salinidade e temperatura e os dados bióticos densidade e composição do zooplâncton. Foram realizadas seis amostragens em 12 estações de coleta a partir de arrastos de superfície horizontais, utilizando redes de malha de 200 μm com uma abertura de 60 cm de diâmetro e um medidor de vazão acoplado. Foram identificados um total de 34 táxons holoplanctônicos e cinco grupos de meroplâncton. Em relação a variação espacial e temporal do zooplâncton da lagoa, os parâmetros avaliados apresentaram resultados significativos para ambos os fatores. As variações também apresentaram maior riqueza, diversidade e densidade de espécies nas estações de coleta mais próximas do mar, onde a salinidade foi mais baixa. Houve predominância do holoplâncton durante o estudo, diferente dos resultados encontrados na década de 90.

Diel and tidal periodicity in the responses of early life stages of marine fishes to an estuary opening event in temperate South Africa

Early life stages of fish were monitored in a breach channel during an opening event of the temporarily open/closed East Kleinemonde Estuary. For comparison, early life stages were also collected in the surf zone and estuary mouth region before, during and after the breaching event on a weekly basis. The breach channel was sampled day and night at each midtide state for five consecutive days using a larval fish seine net (mesh 500 µm). Catch per unit effort (CPUE) of mostly postflexion stage larvae increased in the surf zone during opening events with a concomitant peak in abundance in the breach channel. Catch composition included many estuarine associated species typically found in temporarily open/closed estuaries. Predominantly postflexion stage larvae and newly settled juveniles were caught. No overall patterns of diel and tidal use across species were found in the breach channel suggesting some degree of plasticity in recruitment that could be opportunistically driven for most species. However, for the abundant Rhabdosargus holubi (Sparidae), nocturnal flood tides were favoured for movement into the estuary. Natural estuary opening events, especially during peak rainfall in the recruitment season are critical to the early life history strategy of estuary-associated marine fish species.

Length‐to‐weight and length‐to‐length ratios of six cavefish species from the Pearl River Basin, South China

Length-to-weight and length-to-length ratios were estimated for six cavefishes including Yunnanilus longibarbatus, Yunnanilus bailianensis, Yunnanilus jinxiensis, Oreonectes polystigmus, Paranemachilus pingguoensis, and Paranemachilus genilepis from the upper reaches of the Pearl River, Guangxi Province, China (between 106.26E, 23.14N and 111.42E, 24.85N). The fish were captured between May and October in 2018 and 2019 using trap nets (mesh size 7 mm) set in front of selected caves at 6:30–7:30 p.m. and were hauled out at 6:30–7:30 a.m. the next day. After removal, the fish were measured and weighed immediately to the nearest 0.1 cm and 0.1 g, respectively. The regression parameter r2 was between .95 and .98. The total length-to-standard length ratios were also calculated with r2 ≥ .98. This study should provide a useful reference for biological studies and biodiversity conservation of cavefish.