Local overfishing patterns have regional effects on health of coral, and economic transitions can promote its recovery

Overfishing has the potential to severely disrupt coral reef ecosystems worldwide, while harvesting at more sustainable levels instead can boost fish yield without damaging reefs. The dispersal abilities of reef species mean that coral reefs form highly connected environments, and the viability of reef fish populations depends on spatially explicit processes such as the spillover effect and unauthorized harvesting inside marine protected areas. However, much of the literature on coral conservation and management has only examined overfishing on a local scale, without considering how different spatial patterns of fishing levels can affect reef health both locally and regionally. Here, we simulate a coupled human-environment model to determine how coral and herbivorous reef fish respond to overfishing across multiple spatial scales. We find that coral and reef fish react in opposite ways to habitat fragmentation driven by overfishing, and that a potential spillover effect from marine protected areas into overfished patches helps coral populations far less than it does reef fish. We also show that ongoing economic transitions from fishing to tourism have the potential to revive fish and coral populations over a relatively short timescale, and that large-scale reef recovery is possible even if these transitions only occur locally. Our results show the importance of considering spatial dynamics in marine conservation efforts, and demonstrate the ability of economic factors to cause regime shifts in human-environment systems.

Nutrient loading and farm characteristics of giant gourami fish aquaculture systems in Lake Maninjau, Indonesia: basic knowledge of production performance

Background Aquaculture systems for giant gourami, Osphronemus goramy Lacepède (1801), have significantly improved fish production yields and food security in Indonesia. However, these systems also cause serious problems in terms of eutrophication in waterbodies. This study analysed the nutrient loading and farm characteristics of giant gourami in floating cages in Lake Maninjau. Method A total of 20 floating cages were used to record these nutrients in feed supply, female and male juvenile fish, dead fish and harvested fish to estimate nutrient loading. Data on the harvested fish, production cycle, stock number and cage capacity were used to estimate the stocking density, feeding rate, feed efficiency, and net fish yield, and the relationship between feed supply and nutrient loading and farm characteristics was analysed by least squares regression methods. Results A total of 20 floating cages released nutrients into waterbodies at an average rate of 236.27±60.44 kg/cycle for C, 84.52±20.86 kg/cycle for N and 8.70±3.63 kg/cycle for P. On average, fish production for each floating cage (±SD) was 1226±282 kg wet weight/cycle, and the net fish yield was 12.63±2.82 kg/m3/cycle. Survival rates ranged from 86.33 to 95.27%/cycle. The production cycles varied from 160 to 175 days with feed conversion ratios between 1.60 and 1.75, feed conversion efficiencies were between 0.58 and 0.63. The production parameters that had strong relationships with the net fish yield were feed supply (r2=0.960), stocking rates (r2=0.924) and feeding rates (r2=0.961). In contrast, the length of the production cycle was not strongly related to the net fish yield (r2=0.187). Conclusion Nutrient loading from the supplied feed was greater than that from the harvested fish, juvenile fish and dead fish. Increasing the net fish yield in floating cages was better predicted by the stocking densities and feeding levels than by the other factors.

Aktivitas Ekstrak Kasar Enzim Kolagenase dari Organ Dalam Ikan Malong (Congresox talabon) pada pH Berbeda

Enzymes are biocatalysts that function as catalysts in biological functions. Collagenase enzymes have activities that can support product production. Enzyme activity for protein hydrolysis is influenced by several factors such as protein concentration, pH, temperature, substrate, inhibitor and activator. This study was aimed to determine the effect of differences in pH on the crude extract activity of the collagenase enzyme from the internal organs of malong fish. The study used a non-factorial completely randomized design, the treatments used were different pH (6.5, 7.5, and 8.5). This research consisted of several stages, namely sample preparation, extraction of internal organs to produce crude extract of the collagenase enzyme and test the activity of crude extract of the collagenase enzyme based on different pH. The analysis parameters was consisted of the proportion of fish yield, and the enzyme crude extract activity test at different pH. The results showed that malong fish has a proportion of meat 7,2 parts, bone 3,8, internal organs 1, skin 2,1. The yields of crude extract of collagenase enzyme pH 6.5, 7.5, and 8.5 were 60.83%, 64.09%, and 83.15%, respectively. The crude extract activity of collagenase enzyme from the internal organs of malong fish at pH 6.5, 7.5 and 8.5 was resulted in 0.293 U/ml, 0.5877 U/ml, and 0.7767 U/mL. The highest collagenase enzyme crude extract activity was produced at pH 8.5.

Optimization of dietary protein level for good aquaculture practice based carp fattening in ponds under drought prone area of Bangladesh

Good aquaculture practice (GAP) based carp fattening is a potential technique to obtain higher and safe fish production within shorter period in ponds of drought prone area. Sustainability of this technique, however, is constrained by high feed cost and poor water quality. Therefore, as an overcoming effort, three diets (protein content of 20%, 25% and 30%) under three different treatments (T1, T2 and T3) were tested during January-June, 2020 in fattening ponds of carps (Catla, Gibelion catla; silver carp, Hypophthalmichthys molitrix; rohu, Labeo rohita; mrigal, Cirrhinus cirrhosis; and carpio, Cyprinus carpio var. specularis) under Rajshahi district, Bangladesh. Variation in protein level had no significant effect on environmental parameters of pond water. Combined fish yield was found to vary significantly (P<0.05) among the treatments, while feed conversion ratio did not vary significantly. Although second degree polynomial regression analysis identified 28.50% dietary protein for optimal growth of carps but no significant difference between T2 and T3 was found for the total fish yield. However, significantly (P<0.05) highest cost-benefit ratio obtained with the diet containing 25% protein suggested this protein level in diet was profitable for carp fattening in pond.

Environmentally Induced Alternative Livelihood Strategies among the Artisanal Fishers of the Kainji Lake Basin, Nigeria

Living in poverty-driven communities suffering from food insecurity that is escalated as a result of sub-standard exploitation, fishery resources, and other environmental challenges, small-scale Nigerian artisanal fishers have dominated the fisheries sub-sector. Sadly, environmental changes have reduced Kainji Lake's inflow levels from 393,369m/cu3 in 1994 to 307,231m/cu3 in 2011, accordingly reducing the fish yield by 24025 metric tons in the same period, which has put innumerable Nigerian beneficiaries livelihood at serious risk. The study aimed to devise and propose an adaptive strategy model using the concept of sustainable livelihoods approach. This study mainly depended on distributing questionnaires among thirty fishing communities as the data collection method and provided supplementary data from officials. The results indicated that a set of four livelihood activities yields optimum outcomes. This paper also discusses its implications.

Prospects of Fisheries development in Ox-Bow lakes of Eastern Uttar Pradesh specially in Ballia district

The present article deals with the fisheries development of three important Ox-Bow Lakes of Ballia district of eastern Uttar Pradesh in relation to physico-chemical and biological conditions. The results were found conducive for Fisheries development. The results indicate clearly that potential fish yield is not being realized from the lakes and there is immense scope for increase in Fish production.

Water quality and fish diversity of Federal University of Agriculture Abeokuta reservoir

Federal University of Agriculture reservoir is one of the recently constructed in Abeokuta, Ogun state, Nigeria, therefore the need to assess the water quality, fish diversity and catch assessment of this new water body. Data on fish species were collected on a forthnight basis using multi-stage gillnet sampling techniques for four months (September- December, 2011). Three sampling stations were randomly selected from the entire reservoir. A variety of sampling methods were used at each site in order to reach every fish species. At the river channel and the floodplain sites, traps, cast nets (2.55cm mesh), seine nets (2.55 x 2 cm mesh), monofilament nylon gillnets (15.55 cm mesh), and hook and line were employed. Efforts were made in order to catch fish species in large abundance. Some sampled fish (dead) were collected and placed in cool boxes and examined within 18 hours of capture. Others were preserved in 15% formalin and stored for later examination. A total of 863 fish specimens were caught during the study period. These were identified and classified into 5 species belonging to 3 families. The percentage species composition of the harvest by numbers and weight for all fish species that contributed more than 1% in all the stations combined, were computed. Study of the physico-chemical parameter such as dissolved oxygen ranged from 5.03 to 7.19mg/l; 26 to 280C temperature; 64.8 to 148ppm alkaline; pH 6.67-6.90; 32.5 to 53.5m transparent; 8.86 to 13.72mg/l nitrate; 0.58 to 0.64mg/l phosphate; 0.024 to 0.069 o/oo saline; 103-270cm deep. pH and water temperature serve as variables since the fluctuation of one affects the values of others. The water quality parameters were favourable for fish production. The gillnet fisheries indicated that different mesh sizes of experimental gillnets were sensitive to different fish species. 67.2mm, 78.4mm and 112mm, mesh sizes were efficient in catching Clarias gariepinus, Barbus occidentalis and the Cichlids respectively. The study has shown that middle water was the most suitable habitat for fish in the reservoir. Water level and temperature were observed to guarantee high fish yield in the reservoir.

Effect of Bamboo Substrate on Growth and Production of Carp and Small Indigenous Fish

A field trial was conducted to examine effects of substrates on yield of carp and SIS at Sukranagar Village, Chitwan district for 210 days in farmer’s pond. The experiment was designed with four treatments: T1 (carp only), T2 (carp+SIS), T3 (carp+substrate) and T4 (carp+SIS+substrate) with four replicates. Ponds were stocked with fingerlings of six carp species at a rate of 20,000 fish/ha and two Small indigenous fish species at a rate of 50,000 fish/ha in 1:1 ratio. Prior to stocking of fish, split bamboo mats were fixed in substrate ponds covering 2% of pond surface area to enhance periphyton growth. Carp were fed with dough of rice bran and mustard oil cake (1:1) at the rate of 3% BW daily while Grass carp was fed with grass and banana leaves at 50% BW. Growth and yield of Rohu and Common carp, combined net fish yield and gross margin were found higher (p<0.05) in carp ponds with substrate.

EVALUATING CONDITIONS AND EFFICIENCY OF AQUATIC BIOLOGICAL RESOURCES REPRODUCTION IN LAKE TSATSA UNDER ANTHROPOGENIC LOAD ON LAKE ECOSYSTEM

The paper presents for the first time the results of long-term observations of the conditions and efficiency of the natural reproduction of aquatic biological resources in Lake Tsatsa in-cluded in the Sarpinsky lakes system. In a comparative aspect, the data from studying the commercial fish natural reproduction during 2016-2019 are presented (according to the juvenile fish yield). There has been considered the species composition, as well as the changes of juvenile abundance on the spawning grounds of Lake Tsatsa under different hydraulicity of spring floods during the observed period. The species composition of the main commercial fish juveniles is represented by 10 species. The most stable natural reproduction (high productivity of juveniles) was observed in roach, rudd and perch. Over the entire observation period, the number of roach juveniles dominated by 1.23-3.87 thousand sp./ha. The abundance of pike perch, pike, silver bream and tench has also remained stable for four years, but with the lower quantitative characteristics. The analysis of data on the productivity of juveniles showed that the water regime had the most significant effect on the natural reproduction of carp in Lake Tsatsa. The efficiency of its natural reproduction increases significantly in a high-water year (by 6-32 times) compared with dry years. The influence of hydrological and temperature regimes on the efficiency of natural reproduction of commercial fish has been shown. The terms of spawning of the most abundant commercial fish species are given. The main factors of the anthropogenic impact affecting the ecosystem of Lake Tsatsa and reducing the abundance of the aquatic biological resources reserves due to their natural reproduction have been determined. The data obtained in the course of the research will help solving the problem of amending and supplementing the fishing rules, since there were no terms (periods) in the rules for placing a ban on catching aquatic biological resources for this reservoir