Fish and Fisheries

Dead Zones ◽  
2021 ◽  
pp. 124-137
Author(s):  
David L. Kirchman
Keyword(s):  
Benthic Invertebrates ◽  
Dead Zone ◽  
Fishing Industry ◽  
Aquatic Life ◽  
Dead Zones ◽  
Mobile Species ◽  
Sessile Invertebrates ◽  
Seafood Industry ◽  
Shrimp Fisheries ◽  
The Impact

As the cause of dead zones became understood, research was devoted to figuring out the impact of hypoxia on aquatic life. The Gulf of Mexico dead zone overlaps with the Fertile Fisheries Crescent that stretches from Alabama to Texas, home to a multibillion dollar seafood industry. The chapter argues that the effect of hypoxic waters on benthic invertebrates is clear, while the story for mobile species like fish is complicated. Sessile invertebrates on the bottom, food for many fish and other animals, are wiped out when dissolved oxygen disappears. This chapter explains that even when mobile organisms are able to swim away to oxygen-rich waters, they are concentrated into a smaller habitat where they are more easily caught by predators and fishers. In the Gulf, the effects of hypoxia on fisheries are difficult to separate from the response of the fishing industry and overfishing, but effects especially on shrimp fisheries have been documented. As the chapter summarizes, hypoxia has many other impacts on aquatic biota, including rearranging food webs and contributing to the rise of jellyfish in coastal waters. Even when fishing yields are not affected, dead zones can devastate aquatic life and habitats.

scholarly journals Open ocean dead zones in the tropical North Atlantic Ocean

2015 ◽  
Vol 12 (8) ◽  
pp. 2597-2605 ◽  
Author(s):  
J. Karstensen ◽  
B. Fiedler ◽  
F. Schütte ◽  
P. Brandt ◽  
A. Körtzinger ◽  
...  
Keyword(s):  
North Atlantic ◽  
North Atlantic Ocean ◽  
Dead Zone ◽  
Marine Ecosystem ◽  
High Surface ◽  
Open Ocean ◽  
Depth Range ◽  
Low Oxygen ◽  
Dead Zones ◽  
Tropical North Atlantic

Abstract. Here we present first observations, from instrumentation installed on moorings and a float, of unexpectedly low (<2 μmol kg−1) oxygen environments in the open waters of the tropical North Atlantic, a region where oxygen concentration does normally not fall much below 40 μmol kg−1. The low-oxygen zones are created at shallow depth, just below the mixed layer, in the euphotic zone of cyclonic eddies and anticyclonic-modewater eddies. Both types of eddies are prone to high surface productivity. Net respiration rates for the eddies are found to be 3 to 5 times higher when compared with surrounding waters. Oxygen is lowest in the centre of the eddies, in a depth range where the swirl velocity, defining the transition between eddy and surroundings, has its maximum. It is assumed that the strong velocity at the outer rim of the eddies hampers the transport of properties across the eddies boundary and as such isolates their cores. This is supported by a remarkably stable hydrographic structure of the eddies core over periods of several months. The eddies propagate westward, at about 4 to 5 km day−1, from their generation region off the West African coast into the open ocean. High productivity and accompanying respiration, paired with sluggish exchange across the eddy boundary, create the "dead zone" inside the eddies, so far only reported for coastal areas or lakes. We observe a direct impact of the open ocean dead zones on the marine ecosystem as such that the diurnal vertical migration of zooplankton is suppressed inside the eddies.

scholarly journals Continuous Monitoring of Turbidity and Conductivity in Wastewater Networks

2015 ◽  
Vol 28 (1) ◽  
pp. 9-17 ◽  
Author(s):  
Thomas Bersinger ◽  
Isabelle Le Hécho ◽  
Gilles Bareille ◽  
Thierry Pigot ◽  
Alexandre Lecomte
Keyword(s):  
Total Nitrogen ◽  
Continuous Monitoring ◽  
Oxygen Demand ◽  
Rain Event ◽  
Aquatic Life ◽  
Pollutant Concentrations ◽  
Rain Events ◽  
The One ◽  
Continuous Estimation ◽  
The Impact

Continuous monitoring of the sanitation network of the urban catchment of Pau (southwest France) has been performed since March 2012 using rain gauges, flowmeters, as well as turbidity and conductivity probes. Good correlations were obtained between turbidity, total suspended solids (TSS) and chemical oxygen demand (COD) on the one hand, and conductivity and total nitrogen on the other hand. This allowed an instantaneous and continuous estimation of pollutant concentrations and fluxes since that date. In the present paper we focused on the results of October 2012, which was characterized by alternating periods of dry and rainy events. Turbidity and conductivity raw data show different trends during the study period depending on the parameter and the rain events. A turbidity peak is observed at the beginning of each rain event but its amplitude varies with the intensity of the rain and the length of the preceding dry weather period. Conversely, conductivity decrease during each rain event implying, that rain water acts as a dilution factor. The behaviour of COD and total nitrogen differ markedly due to their partitioning between the dissolved (total nitrogen) and particulate phases (COD). Daily pollutant fluxes allow a global comprehension and monitoring of the sewer system. Important COD fluxes during a rain event preceded by a long dry weather period highlight the importance of erosion of sedimentary deposits in the sewerage network. During these events, important fluxes are discharged into receiving water leading to the question of the impact on aquatic life. Generally, these results highlight the potential of online monitoring to better understand the behaviour of the sewer network on long or short time scales. This could be a useful tool to manage wastewater treatment.

scholarly journals Sooty tern (Onychoprion fuscatus) survival, oil spills, shrimp fisheries, and hurricanes

PeerJ ◽  
2017 ◽  
Vol 5 ◽  
pp. e3287 ◽  
Author(s):  
Ryan M. Huang ◽  
Oron L. Bass Jr ◽  
Stuart L. Pimm
Keyword(s):  
Climate Change ◽  
Oil Spills ◽  
Shrimp Fishery ◽  
Technological Advances ◽  
Face Threats ◽  
Shrimp Fisheries ◽  
Onychoprion Fuscatus ◽  
Sooty Tern ◽  
The Impact

Migratory seabirds face threats from climate change and a variety of anthropogenic disturbances. Although most seabird research has focused on the ecology of individuals at the colony, technological advances now allow researchers to track seabird movements at sea and during migration. We combined telemetry data on Onychoprion fuscatus (sooty terns) with a long-term capture-mark-recapture dataset from the Dry Tortugas National Park to map the movements at sea for this species, calculate estimates of mortality, and investigate the impact of hurricanes on a migratory seabird. Included in the latter analysis is information on the locations of recovered bands from deceased individuals wrecked by tropical storms. We present the first known map of sooty tern migration in the Atlantic Ocean. Our results indicate that the birds had minor overlaps with areas affected by the major 2010 oil spill and a major shrimp fishery. Indices of hurricane strength and occurrence are positively correlated with annual mortality and indices of numbers of wrecked birds. As climate change may lead to an increase in severity and frequency of major hurricanes, this may pose a long-term problem for this colony.

scholarly journals Physicochemical Parameters of Gomati River at Lucknow in Uttar Pradesh (India)

2021 ◽  
Vol 9 (VII) ◽  
pp. 875-886
Author(s):  
Azad Kannaujiya
Keyword(s):  
Water Pollution ◽  
Water Quality ◽  
River Water ◽  
Industrial Effluent ◽  
Oxygen Demand ◽  
Total Hardness ◽  
Domestic Waste ◽  
Aquatic Life ◽  
Gomati River ◽  
The Impact

Gomati River originate from Madhoganj Tanda village in Pilibhit district, U.P. it passes through the district of Shahjahanpur, kheri, Hardoi, Sitapur, Janpur and ultimately merge in Ganga. River water is significant for every living organism as well as aquatic life. Water pollution is a major global problem. Modernization and urbanization have polluted the river water and degraded the status. All over the world we are seeing that drain is the main source of water pollution especially for rivers flowing within the city. This drain generally carries industrial effluent, domestic waste, sewage and medicinal waste resulting in poor water quality. Gomati River receives industrial as well as domestic waste from various drains of Lucknow city. As Gomati river is the only source of surface water near the communities. A total 20 parameters namely Temperature, pH, Turbidity, Conductivity, Total dissolved solids (TDS), Total suspended solids (TSS), Total solids (TS), Dissolved oxygen (DO), Biological oxygen demand (BOD) Chemical oxygen demand (COD), Alkalinity, Total hardness, Calcium as ca, Magnesium as Mg, Chloride, Fluoride, Sulphate as So4, Nickel as Ni, Lead as Pb, and Zinc as Zn where analysed and their variation is discussed to obtain the impact of effluents on water quality. From the result it was found higher than the permissible limit of WHO and BIS.

Managing the Impacts of Human Activities on Fish Habitat: The Governance, Practices, and Science

2015 ◽  
Keyword(s):  
Benthic Invertebrates ◽  
Marine Mammals ◽  
Fish Habitat ◽  
Fishing Gear ◽  
Governance Practices ◽  
Coexisting Species ◽  
The Government ◽  
The Impact ◽  
Poor Infrastructure ◽  
Technical Measures

<em>Abstract.</em>—Mexico is an important producer of fish resources, contributing 1.5% to the total world production. However, most of the fisheries are overexploited or fished to the maximum sustainable level as a result of problems such as overexploitation, poor infrastructure, poaching, limited knowledge of fishing laws, high discard rates, weak fisheries institutions, and little ability to research and manage these difficulties. To solve these problems, the National Program of Fisheries and Aquaculture was established in order to achieve sustainability in Mexican fisheries with the participation of the government, the fishing industry and research institutions. The program has been implemented for the 22 main fisheries of the country, notably the tuna, shrimp and shark fisheries, for which technical measures have been implemented for controlling the catch, the effort and the impact on coexisting species. Specifically, these measures have been aimed at reducing the bycatch of marine mammals and turtles, demersal and benthopelagic fishes and benthic invertebrates. Also, measures have been implemented to mitigate impacts of fishing gear on the benthos and coral reefs. However, many issues still need to be resolved both for these and other lower revenue fisheries, which are important in terms of their effect on ecosystems.

scholarly journals Active Disturbance Rejection Position Synchronous Control of Dual-Hydraulic Actuators with Unknown Dead-Zones

Sensors ◽  
2020 ◽  
Vol 20 (21) ◽  
pp. 6124
Author(s):  
Lixin Wang ◽  
Dingxuan Zhao ◽  
Fucai Liu ◽  
Qian Liu ◽  
Zhuxin Zhang
Keyword(s):  
Disturbance Rejection ◽  
Position Control ◽  
Dead Zone ◽  
Lyapunov Theory ◽  
Least Square ◽  
Synchronization Control ◽  
Hydraulic Actuator ◽  
Dead Zones ◽  
Hydraulic Actuators ◽  
Active Disturbance Rejection

In this paper, an integrated control strategy of position synchronization control for dual-electro-hydraulic actuators with unknown dead-zones is proposed. The unified control scheme consists of two parts: One is adaptive dead-zone inverse controllers of each hydraulic actuator to offset the unknown dead-zones. The other is the linear active disturbance rejection controller (LADRC) for position synchronization error. First, the model of the electro-hydraulic proportional position control system (EPPS) was identified by the forgetting factor recursive least square (FFRLS) algorithm. Next, the model reference dead-zone inverse adaptive controller (MRDIAC) was developed to compensate for the delay of actuator response caused by unknown proportional valve dead-zones. Meanwhile, the validity of the adaptive law was proven by the Lyapunov theory. Therefore, the position control accuracy of each hydraulic actuator is guaranteed. Besides, to improve the precision of position synchronization control of dual-hydraulic actuators, a simple and elegant synchronous error-based LADRC was adopted, which applies the total disturbances design concept to eliminate and compensate for motion coupling rather than cross-coupling technology. The performance of the proposed control solution was investigated through extensive comparative experiments based on a hydraulic test platform. The experimental results successfully demonstrate the effectiveness and practicality of the proposed method.

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