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The fish was yet to complete 50-55% of growth as at the time of capture at Lc, L25 and L75 compared to L, hence, Lopt = 10.1 cm TL, provides least impact on the stock. The length-at-first capture Lc = 5.64 cm TL at age 1.7 yr. Results indicate the fishery is lightly exploited with current exploitation ratio, Ecur = 0.38 < Eopt = 0.5 rate of exploitation, μ = 0.3481 year-1 < Ecur, 35% of the available stock being fished annually corroborated by Z/K ratio (< 2) and M/K = 2.08, indicating environmental stability. The computed total mortality, Z = 2.54 year-1, natural mortality, M = 1.58 year-1 and fishing mortality, F was 0.96 year-1. The estimated growth performance index, φ′ = 2.444 based on length and φ = 0.6833, using weight. The von Bertalanffy exponential growth parameters were estimated as: asymptotic length (L∞) = 13.7 cm TL, growth curvature (K) = 1.48 year-1 and length-at-age zero years, t0 =-0.13 Lo = 2.40 cm TL. Three year classes with mean lengths of 7.4 cm, 11.55 cm and 13.3 cm TL, respectively, were identified. The length-weight relationship of the species indicated isometric growth (b = 3.005 r = 0.9623). In complex piping systems, especially within the unit/plant building where orthographic views do not illustrate the details of design fully, pictorial view in isometric presentation is drawn for clarity.The population dynamics of Odaxothrissa mento in the lower Cross River, southeast Nigeria, were obtained from a six month length composition data (4.25-14.75 cm TL mean = 5.91 cm ± 1.02 and 0.71-7.36 g 1.62 g ± 1.24 n = 1012).

Orthographic symbols are available in templates that are used for speeding up the manual drafting and also the symbol library for computer aided drafting.

Most commonly used symbols are in Table 1. To represent a three plane piping in two dimensions of the paper, certain symbols are followed. These drawings are called the General Arrangement of Piping.

Isometric Views Piping layout is developed in both plan view and elevation view and section / details are added for clarity wherever necessary.

There are two types of views used in the piping drawings: a) Orthographic.- Plans and Elevations b) Perspective. Piping Engineers derive basics from these to represent the pipeline routing on the drawing. The machine drawings and the geometrical drawings are taught in the basic engineering curriculum. The drawings are always considered as the language of engineers.