Effects of shear on eggs and larvae of striped bass, morone saxatilis, and white perch, M. americana

Shear stress, generated by water movement, can kill fish eggs and larvae by causing rotation or deformation. Through the use of an experimental apparatus, a series of shear (as dynes/cm2)-mortality equations for fixed time exposures were generated for striped bass and white perch eggs and larvae. Exposure of striped bass eggs to a shear level of 350 dynes/cm2 kills 36% of the eggs in 1 min; 69% in 2 min, and 88% in 4 min; exposure of larvae to 350 dynes/cm2 kills 9.3% in 1 min, 30.0% in 2 min, and 68.1% in 4 min. A shear level of 350 dynes/cm2 kills 38% of the white perch eggs in 1 min, 41% in 2 min, 89% in 5 min, 96% in 10 min, and 98% in 20 min. A shear level of 350 dynes/cm2 applied to white perch larvae destroys 38% of the larvae in 1 min, 52% in 2 min, and 75% in 4 min. Results are experimentally used in conjunction with the determination of shear levels in the Chesapeake and Delaware Canal and ship movement for the estimation of fish egg and larval mortalities in the field.

Synopsis of biological data on the sand perch, Diplectrum formosum (Pisces: Serranidae)

Information on the biology and fishery resources of a common western Atiantic serranid, Diplectrum formosum, is compiled, reviewed, and analyzed in the FAO species synopsis style. (PDF file contains 27 pages.)

Rents drain in fishery: the case of Lake Victoria Nile Perch fishery

Many fisheries are potentially very valuable. According to a recent report by the World Bank and the FAO (2008), global fisheries rents could be as high as US$ 40-60 billion annually on a sustainable basis. However, according to the report, due to the “common property problem”, most fisheries of the world are severely overexploited and generate no economic rents. The Lake Victoria Nile perch fishery could be among the most valuable fisheries in the world. Unfortunately, also this fishery has fallen prey to the common property problem with excessive fishing effort, dwindling stocks and declining profitability. As a result, there is a large and growing rents loss in this fishery (compared to the optimal) reducing economic welfare and economic growth opportunities in the countries sharing this fishery. As in other fisheries, the biological and economic recovery of this fishery can only come though improved fisheries management

Managing Nile perch using slot size: is it possible?

The fishery of Lake Victoria became a major commercial fishery with the introduction of Nile perch in 1950s and 1960s. Biological and population characteristics point to a fishery under intense fishing pressure attributed to increased capacity and use of illegal fishing gears. Studies conducted between 1998 to 2000 suggested capture of fish between slot size of 50 to 85 cm TL to sustain the fishery. Samples from Kenya and Uganda factories in 2008 showed that 50% and 71% of individuals processed were below the slot size respectively. This study revealed that fish below and above the slot has continued being caught and processed. This confirms that the slot size is hardly adhered to by both the fishers and the processors. The paper explores why the slot size has not been a successful tool in management of Nile perch and suggests strategies to sustain the fishery

The Windermere perch and pike project: an historical review

This paper is an attempt to set the background, provide a brief history, review some of the Windermere perch and pike project's scientific achievements, note current developments and hopes for the future, and comment on some aspects of such long-term projects. The project was originally started in 1939 in order to provide fish in freshwater lakes which might be harvested to enhance the supplies of food in a country subject to blockade. Pike traps and gill-netting were trialed as fishing methods. Catch statistics are available from 1939 which can be used to study population dynamics or for modelling purposes. The author provides an overview of changes in the population dynamics of perch and pike but covers briefly other species like arctic charr and brown trout. Also covered are several aspects of the basic biology and ecology of the principal species involved.

'Fa Tsai', a Chinese edible Nostoc in market. [Translation from: Bulletin of the Japanese Society of Phycology 8 124-126, 1960. ]

The Nostoc 'Fa Tsai' is sometimes seen in Chinese cooking materials stores. It is investigated what 'Fa Tsai' consists of and where it originates.

Effects of suspended sediments on the development of eggs and larvae of striped bass and white perch

The possible ecological effects of suspended sediments are manifold. Briefly, suspended sediments may cause an increased surface for microorganism growth, fewer temperature fluctuations, chemical adsorption or absorption, blanketing, mechanical-abrasive actions, and light penetration reduction (Cairns, 1968). Sherk and Cronin (1970) have pointed out that the above effects have been little studied in the estuarine environment. The ecological effects of suspended sediments on fish eggs and larvae may be of prime importance t o the C and D Canal area, an important spawning and primary nursery area for a variety of estuary: e species (Johnson,1972). This section discusses the effects of suspended sediment on the eggs and larvae of striped bass and white perch.

Diurnal periodicity of activity in the spawning perch P. fluviatilis L. [Translation from: Kalamies 1972(7) 3, 1972]

Diurnal periodicity of spawning in the perch so far are rather meagre and found to be partly contrary to experiences of perch anglers. Therefore a study was made on the spawning during a 5-day period in the spring of 1971 in the Kuusamo area. Observations were made during the main spawning season, between 4- 9 June 1971. The perch were often measured, weighed and then released back into the water. The differences between spawning and non-spawning perch were studied as well as the time of roe discharge in a 24 hour period. Activity and environmental factors such as light intensity were also taken into consideration.

Diurnal periodicity of winter activity in the perch, Perca fluviatilis L. [Translation from: Kalamies 1973(1) 3.]

Since 1967 data have been collected on the distribution of fish caught in a 24 hour period during the winter angling season. The present study on activity periods is based on data from nearly 2000 perch collected between 1967 and 1971. The distribution of number of fish caught during 24 hrs during December - May was studied. Of the total, the most productive period was found to be between 0600 - l600 hrs., with the peak period occurring between 0800 - 1000 hrs. The present data together show that during the darkest months of the year, the perch is only active in the mid-day period. Throughout the whole winter fishing season, activity only occurs during the time between surise and sunset.

Seasonal variation in the diurnal periodicity of activity of the perch, Perca fluviatilis L. [Translation from: Kalamies 1973(3) 3.]

The most common catch of the amateur angler is the perch and it is the diurnal periodicity of activity (& catchability) which is examined in this study based on earlier articles and manuscripts by the authors. Of all environmental factors, variation in light and temperature are the chief reasons in establishing the times of activity periods. Winter, summer and autumn activity was studied. The spawning perch was found to be more active than the non-spawning perch. The time of day in which the fish may be active is dependant on its ability to sense changes in the external environment. Its adaptation to light is the reason for day-activity in the winter, and also accounts for the fact that hardly any activity occurs between sunset and sunrise when this period exceeds 6 hours.

Activity of perch, Perca fluviatilis L. in relation to water temperature [Translation from: Kalamies 1973(6) 4.]

Catchability and activity of Perca fluviatilis in relation to temperature is examined. The number of fish caught and water temperature during the 3 summer months was used the assess the numbers of hours of activity of perch. Parallel to the research on activity, large-scale marking was carried out to establish the periods of growth during the year.

On the diel rhythm of motor activity in perch [Translation from: Informatsionnyi Byulleten Biologiya Vnutrennikh Vod No.30, 12-14, 1976]

The river perch (Perca fluviatilis L.) is most active in the daytime hours, and displays seasonal changes of diel rhythm with a break of the rhythm in spring and autumn. In the present work data were obtained on the motor activity of 3 perch measuring l8-20 cm, caught by net in the littoral of a reservoir and spawned under laboratory conditions. The degree of intensity of movement of perch was judged by special experiments. The results are summarised in this short paper.

Selectivity of gillnets for Nile perch, Lates niloticus (L.), in Lake Victoria, Kenya

Four fleets of hanging coefficients 0.2, 0.4, 0.6 and 0.8 were used to determine size selectivity and selection factors of Nile perch populations. There was a linear relationship between mesh size and modal length of capture. Positively skewed length frequency distributions were found for smaller mesh sizes with entanglement becoming more prominent in mesh sizes above 101 mm. Nets of 114 to 141 mm stretched mesh yielded higher economic returns than small meshes, the catch consisting of few largefish.

Influence of starvation on selected temperatures in the young of bream, roach and perch [Translation from: Informatsionnyi Byulleten Biologiya Vnutrennikh Vod No.50, 45-47, 1981]

Works devoted to the influence of starvation on temperature selection by fishes are few and their conclusions are contradictory. This study determined the influence of brief, up to 14 days, starvation on temperature selection by young fishes. The experiments were carried out in August-September 1976 on fingerling bream (Abramis brama L.), roach (Rutilus rutilus L.) and perch (Perca fluviatilis L.) with body lengths of 3-5 cm and weight 0.5-1.2 g. The young fish were caught in the littoral by seine-nets or small drag-nets. Immediately after catching the fish they were put in acclimatization boxes. The period of acclimatization did not exceed 2 days for bream and roach at a temperature of 20 °C and 6 days for perch at 17 °C. Before the start of the experiment and for the first 10 days of the experiment the fish were fed with oligochaetes, earthworms and daphnia, after that feeding discontinued. At the end of a 10-14 day period the giving of food was resumed. The study concludes that the experiments have shown that in the summer season the factor of starvation significantly changes the reaction to the gradient of temperature in young cyprihids - roach and bream.

Year class strengths of perch and pike in Windermere

The pike (Esox lucius) year classes are more stable than those of the perch (Perca fluviatilis), and have been shown to be closely correlated with temp conditions during the first few months of life. The perch year class strengths have been more variable; for success they require the presence of several positive conditions and the absence of many adverse conditions which could cause failure, a favourable combination of circumstances rarely occurs. The conclusions refer only to Windermere from 1941-1964.