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Acoustic information applied to 4D environmental studies in the Baltic

100%

Orlowski A.

Oceanologia

2006

tom 48

nr 4

Since 1981, acoustic information collected in the form of calibrated measurements of integrated echo energy has been applied at the Sea Fisheries Institute to observe the relationships between fish distribution and environmental factors. Data gathered in different seasons for each elementary distance unit (EDSU) at standardised depth intervals were compared to the values of selected environmental parameters measured in parallel. Acoustic, biological and hydrological data were correlated in space and transferred to the complex database, enabling 4D analysis of numerous factors characterising a wide range of fish behaviour. A number of methods and standards of comparisons are described to explain how to improve understanding of the relationship between 3D spatial environmental gradients and fish distributions. The results of various case studies, including the influence of hydrologic and seabed characterising factors, illustrate the practical application and validity of the methods. Particular attention is given to indicators of the dependence of local fish biomass density on the temperature structure in the sea.

The effect of subjective fish scale ageing on growth and recruitment analyses: a case study from the UK

80%

Musk R. S., Britton J. R., Axford S. N.

Acta Ichthyologica et Piscatoria

2006

tom 36

nr 1

Re-ageing of scales sampled in 1985 from the population of roach, Rutilus rutilus (L.), of the River Stour, England, revealed a high degree of subjectivity in their ageing, resulting from contrasting interpretations of similar scale features between practitioners. Compared with ages attained in 1985, re-ageing of the scales in 2004 only found agreement >80% at ages 1, 2, and 4 years. By age 9, agreement had dropped to 6%. The re-ageing revealed the presence of year classes that had previously been thought to have already died out and suggested their recruitment strength was associated with water temperatures in the first year of life of cohorts.

Ograniczanie wyników

1 Acta Ichthyologica et Piscatoria

1 Oceanologia

1 Axford S. N.

1 Britton J. R.

1 Musk R. S.

1 Orlowski A.

2 2006

Wyniki wyszukiwania

Acoustic information applied to 4D environmental studies in the Baltic

The effect of subjective fish scale ageing on growth and recruitment analyses: a case study from the UK