Haltbarkeit von Nordsee-Wittling (Merlangius merlangus) bei Lagerung in schmelzendem Eis

North-Sea whiting shows a much shorter shelf life in melting ice than other gadoid fishes like saithe, cod and haddock. It can be stored for a maximum of 14 days in ice before being rated as unfit for human consumption. Appropriate freshness indicators for whiting are: sensory tests, dimethylamine- and trimethylamine oxide-nitrogen, creatine content. Of most value for whiting is the determination of thc electric resistance by the fishtester VI.

Effect of electric stimulation on heart beat and body muscle in fish

The effect of AC and DC electric stimulations on the heart-rate and the entire body of Heteropneustis fossillis, Tilapia mossambica and Macrobrachium rosenbergii were studied and presented in kymograph tracings. The reaction of spinal cord in Puntius ticto, Heteropneustis fossilis and Tilapia mossambica to D. C. field was observed to find out its role in electric shocks. A test-check of the electrical resistance of a few species was also conducted. The effect of D. C. and A.C. on the body muscle was found to be the same as that in the case of frog. Different degrees of cardiac slowing were observed in AC and DC. Unbalanced galvanotropic movements were also noticed in spinal fishes.

Food composition and digestive enzymes in the gut of the African electric catfish Malapterurus electricus (Gmelin 1789) (Malapteruridae)

Analyses of stomach contents of 330 Malapterurus electricus (standard length, 10.1-30.5 cm) in Mahin Lagoon (southwestern Nigeria) established it as a bottom feeder. There was a preponderance of insects accounting for >80% occurrence and >25% of total volume in stomachs of specimens, suggesting a stenophagous predatory habit. Qualitative and quantitative assays of digestive enzymes in the different regions of the gut (oesophagus, stomach, duodenum, ileum, rectum) were investigated. Carbohydrases (amylase, maltase), chitinase, proteases (pepsin, chymotrypsin, trypsin) and lipases were detected in different gut regions with different activity. The pattern of distribution and relative activity of the enzymes correlated with the predatory diet

Electric fishing survey of the gravel addition sites on the River Wyre, Grizedale Beck and Joshua's Beck.

Although geographically the River Wyre lies between two rivers containing major migrations of adult salmon and sea trout, its rod & line fisheries have for a number of years produced exceptionally low catches. In order to determine the causes of this the Wyre Salmon and Sea trout Restoration Group (WSSRG) was conceived in 1994 as a partnership between the then National Rivers Authority (now Environment Agency), local landowners, angling clubs and interested parties. Two studies of 1994 and 1995 stated that there is a shortage of useable spawning gravels on the river. This is compounded by Abbeystead Reservoir acting as a gravel trap, the siltation of gravels on several side becks and problems with access to available gravels by returning adults. There was also perceived to be a need for accurate fishery data from the river encompassing redd counts, catch data and surveys of fry populations. The 1995 report suggested a number of management proposals which might be adopted in order to improve and create available spawning habitat for migratory salmonids. Funding was made available to create three spawning gravels on each of two side becks (Grizedale Beck and Joshua's Beck) and the addition of gravels to a site oh the main river below Abbeystead Reservoir. Modifications were also made to the fish pass at Abbeystead to allow easier passage of fish. These improvements were made in the autumn of 1995. Salmonid spawning redd counting was undertaken on the whole Wyre catchment in 1995/1996 and specific surveys by electric fishing on the gravel enhancement sites in the summer of 1996. This report details the current state of the improvement works that were undertaken and presents the results of electric fishing surveys in September 1996. A number of lessons have been learnt which will be of great benefit to the Fisheries Function in other parts of the Wyre catchment and the Central Area in general.

River Ribble sheep dip incident September 1997. Electric-fishing survey report

This report summarises the findings of a series of electric-fishing surveys carried out at four sites on the River Ribble from September 1997 to September 1998. The aims of these surveys were to assess the impact on juvenile salmonids of a pollution incident involving Synthetic Pyrethrin (SP) that occurred near High Birkwith I (SD 802 767) in September 1997.One of these sites was 2.65km upstream of the pollution whilst the remaining three were at varying distances downstream. Data was collected during surveys of the River Ribble in 1992, 97 and 98. The 1997 and 1998 surveys were carried out specifically to monitor for any possible effects of the SP discharge. Data are shown as grades derived from the National Fisheries Classification scheme (NFC). Results are given for the four salmonid life stages; 0+ trout, >0+ trout, 0+ salmon, >0+ salmon and also Total Salmonids.

An investigation into the effects of electric fishing equipment on salmon and sea trout within the area of the Lancashire River Board.

The report looks at experiments into electric fishing equipment and effects on salmon and trout within the Lancashire River Board. Experiments include obtaining information on voltage gradients, ascertaining what damage to fish of the larger size groups resulted from electric fishing, determining whether or not fractures could occur in coarse fish and brown trout,similar to those occurring in salmon and sea trout, and effects low temperatures have on electrofishing techniques.

Measurements of resistance and reactance in fish with the use of bioelectrical impedance analysis: sources of error

New technologies can be riddled with unforeseen sources of error, jeopardizing the validity and application of their advancement. Bioelectrical impedance analysis (BIA) is a new technology in fisheries research that is capable of estimating proximate composition, condition, and energy content in fish quickly, cheaply, and (after calibration) without the need to sacrifice fish. Before BIA can be widely accepted in fisheries science, it is necessary to identify sources of error and determine a means to minimize potential errors with this analysis. We conducted controlled laboratory experiments to identify sources of errors within BIA measurements. We concluded that electrode needle location, procedure deviations, user experience, time after death, and temperature can affect resistance and reactance measurements. Sensitivity analyses showed that errors in predictive estimates of composition can be large (>50%) when these errors are experienced. Adherence to a strict protocol can help avoid these sources of error and provide BIA estimates that are both accurate and precise in a field or laboratory setting.

Using wildlife activity and antibiotic resistance analysis to model bacterial water quality in coastal ponds

Models that help predict fecal coliform bacteria (FCB) levels in environmental waters can be important tools for resource managers. In this study, we used animal activity along with antibiotic resistance analysis (ARA), land cover, and other variables to build models that predict bacteria levels in coastal ponds that discharge into an estuary. Photographic wildlife monitoring was used to estimate terrestrial and aquatic wildlife activity prior to sampling. Increased duck activity was an important predictor of increased FCB in coastal ponds. Terrestrial animals like deer and raccoon, although abundant, were not significant in our model. Various land cover types, rainfall, tide, solar irradiation, air temperature, and season parameters, in combination with duck activity, were significant predictors of increased FCB. It appears that tidal ponds allow for settling of bacteria under most conditions. We propose that these models can be used to test different development styles and wildlife management techniques to reduce bacterial loading into downstream shellfish harvesting and contact recreation areas.

Towing resistance of ottar [i.e. otter] trawls used for shrimps from small mechanised boats

Attempts have been made to determine the towing resistance of the shrimp otter trawls operated from small trawlers off Cochin and the actual resistance on the warps for eight different boats working under the normal fishing conditions have been measured. Engine Horse Power utilised for towing the gear at normal speed and fishing conditions has also been estimated.

Preliminary observations on the effect of a. c. current on Catla catla and Ophicephalus punctatus

In order to evolve suitable electrical fishing gear for inland waters, preliminary experiments have been conducted to observe effect of a. c. currents on Catla catla at voltages of 30, 90 and 120, pH 7.3 and 8.4, temperature 48°F, 78°F and 105°F, distance between electrodes 25 cm, 50 cm and 75 cm, size range of fish 100 mm, to 235 mm. Apparatus used was a 5 kw; a. c. 60 cycles generator with resistance control. Larger sizes of fish were more prone to electric shock. Higher temperature increases the intensity of the shock, while variation of pH between 7.3 to 8.4 did not materially affect the intensity of the shock. Fishing with a mixed population of Catla catla and Ophicephalus punctatus gave a greater percentage of mortality for the latter.

Instrument for the measurement of the fore and aft tilt of otterboards

A portable self-contained instrument has been designed and developed for the measurement of the Fore and Aft tilt of otter boards within the range —22° to + 22° with an accuracy of ± 1°. An underwater transducer fitted on the otter board converts its tilt into corresponding electrical resistance which is measured in an ohmmeter on board, both being connected by electric cable.

Underwater warp tension meter

A self-contained electronic solid-state instrument capable of measuring the tension between the different parts of a trawl net in operation, has been designed and developed for the measurement in the range 0 to 300 kg with an accuracy of ± 2 kg. The instrument is useful for measuring the resistance to motion of various accessories of a trawl net. It consists of an inductive type underwater tension transducer and an electronic indicating meter kept on board the vessel, both the units being connected by electric cable.

Development of an electric shrimp trawl 1. Reaction of shrimps to low volt direct current

Preliminary attempts were made to assess the effect of direct current on shrimps and to see whether the shrimp could be guided in large numbers into the fishing net by using a current of appropriate voltage without scattering them away as it happens at present. This communication is the first in the series of studies and primarily deals with laboratory equipment and experimental procedures followed.