Growth model of the reared sea urchin Paracentrotus ... - SciViews

YY
3
2.5
2
1.5
1
0.5
General introduction
⎛ 1 ⎞
2 2
Yt () = ⎜ ⎟⋅ln2
b⋅( t− t0) + 2 b⋅( t− t0) + ab ⋅ + d
⎝ b ⎠
(17)
This complex 4-parameter model has an initial period of slow growth, a
period of exponential growth followed by an indefinite period of slow
growth (Fig. 16).
2 4 6 8 10 tt
Figure 16. Example of a Tanaka curve with a = 3, b = 2.5, d = -0.2 and t0 = 2.
Modelling sea urchins growth
Table 1 summarizes sea urchin studies using growth models.
Numerous works using growth rate only (final – initial size) are not
included. Most species of economic interest (Tripneustes gratilla,
Sphaerechinus granularis, Psammechinus miliaris, Paracentrotus lividus,
Strongylocentrotus droebachiensis, S. intermedius, S. nudus, S.
franciscanus, Hemicentrotus pulcherrimus) were considered by one or
more authors. They focused either on population dynamics aiming to
provide management criteria for fisheries, or on growth in cultivation.
Other species studied were either key-species in some biotopes (Diadema
antillarum Philippi, Echinus esculentus L.), or animals occupying some
particular biotopes [for instance, deep-sea urchins like Echinosigra phiale
(Thompson) or Hemiaster expergitus Loven].
52