Search results for "Fish"

Immediate Effects of Prescribed Burning on Soil Mite (Acari: Oribatida) Communities in a Scots Pine (Pinus Sylvestris) Forest, Latvia

2021

Abstract Prescribed burning is used to maintain and restore habitats, to protect and increase species bio-diversity. Knowledge about soil fauna is limited, especially on community responses to fire disturbances. The aim of this study was to determine the immediate effects of prescribed burning on soil armoured mite (Acari: Oribatida) communities, vegetation cover and soil physiochemical properties in a boreal Scots pine forest in Latvia. Soil samples were collected on the day of the prescribed burning in the protected landscape area “Ādaži” and 16 days after. No significant changes in abiotic factors were found. Fire significantly decreased the vegetation cover. After the burning, the total…

Echo-sounding can discriminate between fish and macroinvertebrates in fresh water

2008

SUMMARY 1. Acoustic scattering from fish and macroinvertebrates was studied in a boreal Finnish lake at three echosounder frequencies (38, 120 and 200 kHz). Split-beam transducers with partly overlapping 7� beams were employed. Acoustic, fish and invertebrate sampling were undertaken simultaneously. Vertical gradients of temperature and oxygen concentration were measured during the exercise. 2. At all frequencies, a narrow scattering layer coincided with the thermocline. At 38 kHz, fish were detected well with practically no reverberation from invertebrates while 200 kHz detected both fish and invertebrates. 3. Minor differences in the magnitude of acoustic scattering from fish were found b…

Effect of stocking time on yield and location of recapture in two forms of brown trout (Salmo trutta) when stocked in respect to migration activity

2003

Abstract Tagged 2-year-old trout smolts, Salmo trutta , were stocked into River Isojoki in 1996, 1997 and 1998 (a sea trout strain), and Lake Konnevesi in 1997 and 1998 (a brown trout strain) in April, May or June–July. Stocking dates were determined in respect to the migration activity of 100 PIT-tagged fish held in the laboratory. Migration activity was relatively similar in both trout forms each year. In April, movement activity was low; in May, movement activity of the PIT-tagged fish increased and in June–July, movement had ceased. There was a general tendency for lower migration activity in maturing males than for immature fish, but differences were not statistically significant every…

Modeling the distribution of thorny skate (Amblyraja radiata) in the southern Grand Banks (Newfoundland, Canada)

2019

Globally, commercial fisheries have had a strong impact on elasmobranch populations directly through high catch rates and indirectly through bycatch. Consequently, the abundance of many species is declining to the extent that some are considered under threat of extinction. Regionally, this negative trend is also evident in the international waters of the southern Grand Banks (off the coast of Newfoundland, Canada), where the occurrence of the thorny skate (Amblyraja radiata) has declined by nearly 70% in recent decades. This study used Bayesian species distribution models to investigate the habitat preference and biomass trends of the thorny skate during a 14-year period (2003–2017), linki…

The development of the Norwegian wrasse fishery and the use of wrasses as cleaner fish in the salmon aquaculture industry

2017

Norway leads the world aquaculture production of Atlantic salmon Salmo salar and farmed Norwegian Atlantic salmon is currently consumed around the globe. However, sea lice infestation is a major problem faced by the salmon aquaculture industry in Norway and elsewhere. The use of wild-caught cleaner fish, mainly wrasses, has been recommended over the other available methods as the most economical and environmentally friendly option to control sea lice infestation in salmon farming. Here, we review the development of the Norwegian wrasse fishery and the use of wrasses as cleaner fish. In this document, we address the sea lice problem and introduce the main wrasse species employed as cleaner f…

Differential toxicity of simazine and diuron to Torilis arvensis and Lolium rigidum

1990

Summary: In a soil application, Torilis arvensis was nearly as susceptible as Lolium rigidum to simazine but was 18-fold more tolerant to diuron. Treat ment with diuron inhibited photosynthesis in L. rigidum but had only a limited effect in T. arvensis although chloroplasts isolated from both species displayed similar susceptibility. 14C-diuron degradation in plants was limited, with the formation of conjugates of mono-methyl-diuron in T. arvensis and N-dealkylated derivatives of diuron in L. rigidum. 14C-diuron entered the roots and was translocated throughout the leaves of L. rigidum but was restricted to stems, leaf petioles and leaf veins of T. arvensis. This difference in transport pat…

Foreword

2007

Modelling vertical and lateral weed seed movements during mouldboard ploughing with a skim-coulter

2001

Abstract The vertical distribution of weed seeds in soil is crucial because seedling emergence varies with seed depth, whereas lateral soil displacement during mouldboard ploughing contributes to weed dispersal within the tilled field. In order to model vertical and lateral seed displacements during ploughing, an existing model describing soil particle movements for different ploughing characteristics (depth and width) and soil structures was adapted to integrate the effect of a skim-coulter. This model was tested in two field trials, in Northern France, using coloured plastic beads to imitate weed seeds. The trial in Dijon was set up on an eutric cambisol and comprised both compacted and u…

Soil properties and tree growth along an altitudinal transect in Ecuadorian tropical montane forest

2008

In tropical montane forests, soil properties change with increasing altitude, and tree-growth decreases. In a tropical montane forest in Ecuador, we determined soil and tree properties along an altitudinal transect between 1960 and 2450 m asl. In different vegetation units, all horizons of three replicate profiles at each of eight sites were sampled and height, basal area, and diameter growth of trees were recorded. We determined pH and total concentrations of Al, C, Ca, K, Mg, Mn, N, Na, P, S, Zn, polyphenols, and lignin in all soil horizons and in the mineral soil additionally the effective cation-exchange capacity (CEC). The soils were Cambisols, Planosols, and Histosols. The concentrati…

Influence of the marine feeding area on the muscle and egg fatty-acid composition of Atlantic salmonSalmo salarspawners estimated from the scale stab…

2017

Fatty acids in muscle tissue and eggs of female Atlantic salmon Salmo salar spawners were analysed to evaluate the dietary quality of their final feeding areas in the Baltic Sea. The final likely feeding area was identified by comparing stable carbon and nitrogen isotope composition of the outermost growth region (final annulus) of scales of returned S. salar with that of reference S. salar caught from different feeding areas. Some overlap of stable-isotope reference values among the three areas, in addition to prespawning fasting, decreased the ability of muscle tri-acylglycerols to discriminate the final likely feeding area and the area's dietary quality. Among three long-chained polyunsa…