Some Aspects of the Ecology of Lake Macquarie, N.S.W., with Regard to an Alleged Depletion of Fish. XII. Summery Review

1959 ◽  
Vol 10 (3) ◽  
pp. 399 ◽  
Author(s):  
JM Thomson
Keyword(s):  
Heavy Rain ◽  
Entrance Channel ◽  
Commercial Fish ◽  
Fish Catch ◽  
Lake Waters

The nature of the entrance channel determines the peculiar attributes of Lake Macquarie. The food of the fish appears to be derived ultimately from the benthic flora, including epiphytes, rather than from the plankton. In terms of the commercial fish catch per man the lake is as productive as it ever has been; amateur angling is increasing in intensity and in midsummer rivals the effects of the commercial fishermen. The fall in catch of certain species during the decade 1946 to 1955 is attributed to the reduction of food consequent upon stratification of the lake waters after prolonged periods of heavy rain.

scholarly journals ON THE QUESTION OF FISHERY REGIME REGULATION IN THE VOLGA-CASPIAN BASSIN (ASTRAKHAN REGION) BY THE EXAMPLE OF NORTH-CASPIAN ROACH

2018 ◽  
pp. 41-48
Author(s):  
Vitaliy Victorovich Barabanov ◽  
Sergey Yurievich Nikiforov
Keyword(s):  
Hydrological Regime ◽  
Fishing Effort ◽  
Major Purpose ◽  
Spawning Grounds ◽  
Commercial Fish ◽  
Factors Affecting ◽  
Fish Catch ◽  
And Gender ◽  
Negative Factors ◽  
Caspian Roach

The article shows the assessment of fishing conditions of roach catches (the number of fishing grounds, fishing gears, catches, catches per unit of fishing effort, fishing intensity, etc.) at the main fishery objects of the Volga delta. There has been made the analysis of structure of size and gender composition of roach from commercial and amateur catches. The results have shown a depression of the population with negative dynamics in future. There have been determined main negative factors affecting the state of roach stock: unfavorable hydrological regime, incoordination in terms of commercial and amateur catches, limits of catch and size. In such circumstances the major purpose is to create a fishing regime, when maximum pass of fish spawners to spawning grounds is provided. The article proposes organizing a special regime of fishing roach with the aim to introduce additional limitations to the commercial fish catch, the main point of which is a transition from fine-meshed seines to medium-meshed seines in the day, when the water level in the Astrakhan region achieves an index mark as 350 cm. This measure will allow assuring a maximum pass of roach spawners to spawning grounds. A similar interdiction must be valid for amateur fishing. It should be noted that this interdiction is a provisional measure allowing to preserve and reproduce roach population.

Description of the commercial fish catch in Iraqi marine waters

2014 ◽  
Vol 25 (2) ◽  
Author(s):  
K Younis ◽  
A Jabir ◽  
U Yousif ◽  
T Abd-Rassol
Keyword(s):  
Marine Waters ◽  
Commercial Fish ◽  
Fish Catch

scholarly journals Physical Oceanographic Influences on Central Benguela Fish Catch

2012 ◽  
Vol 16 (6) ◽  
pp. 1-15 ◽  
Author(s):  
Mark R. Jury
Keyword(s):  
Vertical Motion ◽  
Principal Component ◽  
Ekman Transport ◽  
Commercial Fish ◽  
Benguela Upwelling ◽  
Fish Catch ◽  
Composite Maps ◽  
Catch Rates ◽  
Eggs And Larvae ◽  
High Fish

Abstract Ocean and atmosphere reanalysis fields are used to study environmental conditions and their relation to commercial fish catch in the central Benguela upwelling zone, using both targeted and objective techniques. Composite maps and sections indicate a 10%–20% weakening of southeasterly winds, a 0.5°C warming of sea temperatures over the shelf, and changes in currents and subsurface upwelling associated with higher fish catch. During periods of high fish catch, recirculating gyres form that may aid the retention of eggs and larvae. Offshore winds contribute to poleward Ekman transport in a 50-m-deep layer within 100 km of the coast. In addition to composite analysis, the natural variability is studied by principal component analysis of wind stress, sea level, temperature, salinity, currents, and vertical motion in the period 1970–2007. Comparison of interannual time scores and fisheries data indicate that anomalous poleward winds and warmer temperatures in the Lüderitz plume, driven by an atmospheric trough in the South Atlantic, are associated with higher catch rates.

Some Aspects of the Ecology of Lake Macquarie, N.S.W., with Regard to an Alleged Depletion of Fish. VIII. Trends of the Commercial Fish Catch and Management of the Fishery

1959 ◽  
Vol 10 (3) ◽  
pp. 354 ◽  
Author(s):  
JM Thomson
Keyword(s):  
Commercial Fishing ◽  
Total Catch ◽  
Commercial Fish ◽  
Injurious Effect ◽  
Nursery Grounds ◽  
Fish Catch

Although the total catch has fallen since 1922 the abundance of fish as measured by the catch per man has not. The total catch has dropped because fewer men are fishing. A red drop in the abundance of certain species, namely flathead, bream, luderick, and sea mullet, occurred between 1945 and 1947; the algal-feeding luderick and mullet regained their abundance by 1951, but the three ground fish had not regained their former abundance by 1957. The trends of the monthly catch are similar in all years, the catch expectation being least reliable in November and most predictable in February. Closing of the northern end of the lake to commercial fishing has resulted in a loss to the consumer of quantities of sea mullet and tailor, species which are fished ineffectively by amateur anglers. During the winter months netting in the northern part of the lake, except in certain bays which form nursery grounds for the young of several species, would have no injurious effect on the stocks.

Lake Kinneret and the Law

1977 ◽  
Vol 12 (3) ◽  
pp. 288-317 ◽  
Author(s):  
Richard E. Laster
Keyword(s):  
Lake Water ◽  
Algal Blooms ◽  
Lake Kinneret ◽  
Commercial Fish ◽  
Fish Catch ◽  
Direct Contrast ◽  
Agricultural Use ◽  
Unique Species ◽  
Purification Plant

In direct contrast to Israel's western flowing streams, Lake Kinneret is used for a multiplicity of beneficial uses. The lake supplies 45% of the country's total water supply, 6% of its fish catch, a vacation spot for 1½ million tourists a year, a purification plant for 3 million cubic metres of sewage yearly, an annual supply of tons of smooth, decorative pebbles, and a source of income for at least 70 scientists.Again in contrast to Israel's streams and wadis, data are available to those interested in preventing pollution of the Kinneret. Scientific studies of the lake began as far back as 1847. Beginning in the 1950's Israel scientists concentrated their efforts on solving a myriad of problems in the lake and its watershed. In the 1950's geographic surveys of the watershed were completed which described the type of land, its quality, texture and suitability for agricultural use. By 1964, scientific studies included the quality of lake water for drinking, lake currents, salt concentrations in the lake, sources of radiation, the lake's temperature, phytoplankton, zooplankton, algal blooms, floating plants, organisms living at the bottom of the lake, the lake's water level, thematodes and nematodes in the lake, water birds, chiromed flies, pesticides, commercial fish, and, last but not least, the Tabgha blind prawn, the only unique species endemic to the lake's waters.

scholarly journals PHYTOPLANKTON AS COMPONENT OF FODDER BASE IN MUNOZERO (LAKE ONEGA BASIN)

2021 ◽  
Vol 2021 (2) ◽  
pp. 66-75
Author(s):  
Yuliya Slastina
Keyword(s):  
Seasonal Dynamics ◽  
Structural Characteristics ◽  
Vegetation Period ◽  
Anthropogenic Pressures ◽  
Fish Food ◽  
Commercial Fish ◽  
Fish Catch ◽  
Average Biomass ◽  
The Republic ◽  
Average Size

The paper presents the results of a study of phytoplankton in Lake Munozero during the vegetation period in 2018. The seasonal dynamics of the biomass and abundance of algae in the southern and northwestern reaches experiencing different anthropogenic pressures has been considered. The reservoir stands out among other water bodies of the Republic of Karelia for its chemical and morphometric characteristics. It is characterized by high mineralization (up to 100 mg/l), isolation of the reaches, low color and content of nutrients and organic compounds. There have been identified 147 taxa of the algoflora with a rank lower than the genus, belonging to 9 divisions. The structure of algocenoses in terms of species richness and quantitative development is determined by representatives of centric diatoms, cyanobacter, dinophytes, and chlorococcal greens, which is important for the formation of the fish food base. Average size of phytoplankton during 2018 in the northwestern reach reached 492 thousand cells/l, the average biomass was 0.468 g/m3. The average size of phytoplankton in the southern reach reached 589 thousand kg/l, the average biomass was 0.459 g/m3. The water quality in the northwestern and southern reaches by the value of the saprobic index corresponds to the III class of waters, but the biomass values characterize both parts of the reservoir as oligotrophic. Shannon's index, quantitative and structural characteristics of phytoplankton differ in the northwestern and southern reaches, seasonal dynamics is not typical for phytoplankton of the oligotrophic Karelian lake. According to the data on abundance and biomass of phytoplankton of Lake Munozero the value of commercial fish catch was calculated.

scholarly journals Catch and discardfish species of trawl fisheries in the Iskenderun Bay (Northeastern Mediterranean) with emphasis on lessepsian and chondricthyan species

2014 ◽  
Vol 15 (2) ◽  
pp. 380 ◽  
Author(s):  
E. YEMISKEN ◽  
C. DALYAN ◽  
L. ERYILMAZ
Keyword(s):  
Fish Species ◽  
Sparus Aurata ◽  
Depth Range ◽  
Commercial Catch ◽  
Commercial Fish ◽  
Mullus Surmuletus ◽  
Iskenderun Bay ◽  
Fish Catch ◽  
Catch Composition ◽  
Trawl Fisheries

Fish species in catch and discard of trawl fisheries in and around Iskenderun Bay were examined within the fishing closure period and fishingperiod.The sampling was performed from May 2010 to January 2011 by a commercial trawl vessel.Chondricthyan species composed 49 % of discard catch biomass whileGymnura altavela and Dasyatis pastinacawere dominant in hauls. 27 lessepsian fish species were captured during the study,nine of them beingtarget species for trawl fisheries. In total, 14 of the lessepsian fish species were determined as discard species.In both sampling periods, Equulites klunzingeriand Citharus linguatula contributed to discard fish catch dissimilarity among depth ranges (deeper and shallower than 60 m). E. klunzingerishowed high abundance in discard catch.There were no significant differences in the distribution of the discard fish biomass between the sampling periods (ANOVA test, p>0.05). However, depth range pointed out significantdifferences in discard fish catch composition (p<0.05).Among major commercial fish species of trawl fisheries, Mullus surmuletus and Sparus aurata were not separated as discard in anyhaul by fishermen. Any size of these two species  were included in commercial catch (Total length ranged from 61 to 721 mm).

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