Establishing growth formula from cuttlebone stripes
Natural life history of cephalopods have been puzzling marine biologists for a long time. Fishery scientists also met with great difficulty in managing resources of squids as well as cuttlefishes. The lack of the accurate equation defining growth through time is one of the major reasons. This was due mainly to no stable characteristic for age determinations. It was known that in anatomy, stripe layers of cuttlebone are similar in embryonic development as shells of the bivalve, which has been used for age determinations.
This study suggested that by taking the stripe marks on the bottom surface of the cuttlebone as quasi-daily-aging characters, it is possible to define the trend of growth of cuttlefish by (either a von Bertalanffy or Gompertz) growth equation. A semi-automatic computer processing system was designed and organized to measure the stripe area lengths (SAL) and lengths of stripe margin (LSM) for all stripe marks upon individual cuttlebone (analogous to scale reading in fishery research for the same purpose) of ¡]Sepia pharaonic Ehrenberg¡A1831¡^. A total of 21 cuttlebones were measured and the data analyzed. It appeared that the growth of the cuttlefishes are still on the stage of acceleration, and is not suitable to be represented by the VBGF curve traditionally used. Using SAL= and LSM= ' as length indicators respectively, two Gompertz growth equations were respectively estimated as followed.
' = 23.18*exp[-4.27*exp(-0.015*t)]
Two functional linear regression formulas were also prepared as:
= -1.2684 + 0.7729 * L
' = -0.7829 + 0.6297 * L
The above formulas can be used for the transformation between SAL (or LAM) and body length.
The well-known Rosa Lee¡¦s phenomenon was not found either based on the character of SAL or LSM, implying that during the trend of growing, the mortality of Sepia pharaonic were not significantly different among different sizes of organisms.
It was expected that with this breakthrough in technique and theory, additional knowledge on the populations biology of cuttlefish can be known in more detail.
Advisor:Chi-lu Sun; Sun-chio Fong; Wann-nian Tzeng
School:National Sun Yat-Sen University
School Location:China - Taiwan
Source Type:Master's Thesis
Keywords:cuttlebone length of striped margin gompertz formula growth area
Date of Publication:08/10/2004