Harmful impact of filamentous algae (Spirogyra sp.) on juvenile crayfish

Abstract

Acta Technologica Agriculturae 1/2016Dušan Páleš et al.The most effective way for determination of curves for practical use is to use a set of control points. These control points can be accompanied by other restriction for the curve, for example boundary conditions or conditions for curve continuity (Sederberg, 2012). When a smooth curve runs only through some control points, we refer to curve approximation. The B-spline curve is one of such approximation curves and is addressed in this contribution. A special case of the B-spline curve is the Bézier curve Rédl et al., 2014). The B-spline curve is applied to a set of control points in a space, which were obtained by measurement of real vehicle movement on a slope (Rédl, 2007(Rédl, , 2008. Data were processed into the resulting trajectory (Rédl, 2012;Rédl and Kučera, 2008). Except for this, the movement of the vehicle was simulated using motion equations (Rédl, 2003;Rédl and Kročko, 2007). B-spline basis functionsBézier basis functions known as Bernstein polynomials are used in a formula as a weighting function for parametric representation of the curve (Shene, 2014). B-spline basis functions are applied similarly, although they are more complicated. They have two different properties in comparison with Bézier basis functions and these are: 1) solitary curve is divided by knots, 2) basis functions are not nonzero on the whole area. Every B-spline basis function is nonzero only on several neighbouring subintervals and thereby it is changed only locally, so the change of one control point influences only the near region around it and not the whole curve.These numbers are called knots, the set U is called the knot vector, and the half-opened interval 〈u i , u i + 1 ) is the i-th knot span. Seeing that knots u i may be equal, some knot spans may not exist, thus they are zero. If the knot u i appears p times, hence u i = u i + 1 = ... = u i + p -1 , where p >1, u i is a multiple knot of multiplicity p, written as u i (p). If u i is only a solitary knot, it is also called a simple knot. If the knots are equally spaced, i.e. (u i + 1 -u i ) = constant, for every 0 ≤ i ≤ (m -1), the knot vector or knot sequence is said uniform, otherwise it is non-uniform.Knots can be considered as division points that subdivide the interval 〈u 0 , u m 〉 into knot spans. All B-spline basis functions are supposed to have their domain on 〈u 0 , u m 〉. We will use u 0 = 0 and u m = 1.To define B-spline basis functions, we need one more parameter k, which gives the degree of these basis functions. Recursive formula is defined as follows:This definition is usually referred to as the Cox-de Boor recursion formula. If the degree is zero, i.e. k = 0, these basis functions are all step functions that follows from Eq. (1). N i, 0 (u) = 1 is only in the i-th knot span 〈u i , u i + 1 ). For example, if we have four knots u 0 = 0, u 1 = 1, u 2 = 2 and u 3 = 3, knot spans 0, 1 and 2 are 〈0, 1), 〈1, 2) and 〈2, 3), and the basis functions of degree 0 are N 0, 0 (u) = 1 on interval 〈0, 1) Acta In this co...

Harmful impact of filamentous algae (Spirogyra sp.) on juvenile crayfish

“…The calculated values of the TL/CL proportion for four-month-old crayfish ranged from 1.88 to 1.94. These are higher than values obtained for younger specimens (one-and two-month olds) from basin rearing (Ulikowski andKrzywosz 2006, 2009). However, according to several sources, the values of this proportion in adults is from 1.90 to 1.96 in males and from 2.00 to 2.05 for females (Kossakowski 1962, Andrzejewski et al 2001, Chybowski 2007.…”

“…Small, shallow ponds are used in crayfish aquaculture to rear juvenile crayfish (Ackefors and Lindqvist 1994, Ackefors 1998, Ulikowski and Krzywosz 2013, Ulikowski et al 2015. Such basins are particularly prone to heavy filamentous algae growth (Ulikowski 2007). This was the motivation for attempting to answer the question of what impact filamentous algae has on juvenile crayfish.…”

Application of microalgae Scenedesmus acuminatus enhances water quality in rice-crayfish culture

“…are detrimental for crayfish cultivation. Ulikowski et al (2015) proved that the presence of filamentous algae ( Spirogyra ) has a strong negative impact on juvenile crayfish survival. It is clear from the present study that microalgal addition can significantly change the water quality of crayfish systems to inhibit the growth of filamentous algae such as Spirogyra .…”

Food web structures of irrigated rice fields estimated from carbon and nitrogen stable isotopes: Special reference to the role of filamentous green algae as a food resource of aquatic consumers

“…However, despite their large abundance, their dietary contribution to aquatic consumers has not been fully elucidated. It was reported that fresh filamentous green algae were less eaten by aquatic consumers likely due to allelochemical substrates (LaLonde et al, 1979;Ulikowski et al, 2015). In contrast, some aquatic consumers such as Haliplidae water beetles are specialists that forage mostly on filamentous green algae (Gundersen & Otremba, 1988;van Vondel et al, 1995).…”