Bertalanffy proposed the differential equation m´(t) = p × m (t) a-q × m (t) for the description of the mass growth of animals as a function m(t) of time t. He suggested that the solution using the metabolic scaling exponent a = 2/3 (von Bertalanffy growth function VBGF) would be universal for vertebrates. Several authors questioned universality, as for certain species other models would provide a better fit. This paper reconsiders this question. Using the Akaike information criterion it proposes a testable definition of 'weak universality' for a taxonomic group of species. (It roughly means that a model has an acceptable fit to most data sets of that group.) This definition was applied to 60 data sets from literature (37 about fish and 23 about non-fish species) and for each dataset an optimal metabolic scaling exponent 0 ≤ a opt < 1 was identified, where the model function m(t) achieved the best fit to the data. Although in general this optimal exponent differed widely from a = 2/3 of the VBGF, the VBGF was weakly universal for fish, but not for non-fish. This observation supported the conjecture that the pattern of growth for fish may be distinct. The paper discusses this conjecture. PeerJ Preprints | https://doi.org/10.7287/peerj.preprints.3303v1 | CC BY 4.0 Open Access | rec Abstract. Bertalanffy proposed the differential equation m´(t) = pm(t) a-qm(t) for the description of the mass growth 10 of animals as a function m(t) of time t. He suggested that the solution using the metabolic scaling exponent a = 2/3 11 (von Bertalanffy growth function VBGF) would be universal for vertebrates. Several authors questioned universality, 12 as for certain species other models would provide a better fit. This paper reconsiders this question. Using the Akaike 13 information criterion it proposes a testable definition of 'weak universality' for a taxonomic group of species. (It 14 roughly means that a model has an acceptable fit to most data sets of that group.) This definition was applied to 60 15 data sets from literature (37 about fish and 23 about non-fish species) and for each dataset an optimal metabolic scaling 16 exponent 0 ≤ a opt < 1 was identified, where the model function m(t) achieved the best fit to the data. Although in 17 general this optimal exponent differed widely from a = 2/3 of the VBGF, the VBGF was weakly universal for fish, 18 but not for non-fish. This observation supported the conjecture that the pattern of growth for fish may be distinct. The 19 paper discusses this conjecture. 20 Keywords: Akaike's information criteria (AIC), multi-model inference, von Bertalanffy growth function (VBGF), 21 metabolic scaling exponent, weak universality 22 1. Introduction 23 Growth models: Size at age is a key metric of productivity for any animal population (MacNeil 24 et al., 2017) and since Verhulst' (1838) seminal work about the logistic function a wide range of 25 growth models to describe the size of animals as a function of time has been developed. Amongst 26 applications are improved otolith analysis fo...

Life history parameters associated with reproductive biology, age, and growth of the convict cichlid (also known as the zebra cichlid) Amatitlania nigrofasciata, which was introduced into the Haebaru Reservoir on Okinawa-jima Island, were estimated using 437 specimens that ranged from 13.7 to 82.9 mm standard length (SL). Lengths of females at first maturity (SL) and 50% maturity (L 50 ) were estimated to be 32.2 and 37.3 mm SL, respectively. The spawning period continued throughout the year, with a peak spawning cycle from March to May 2006-2007. Observations of postovulatory follicles and tertiary yolk stage oocytes indicate that convict cichlids spawn multiple times within a year. Female cichlids that hatched during the peak spawning seasons matured after October of the same year. Batch fecundity of females (32.2-61.2 mm SL) ranged from 65 to 345 (mean ± SD=155±63). Opaque zones along the outer margins of otoliths formed annually. The maximum age of male and female cichlids was 3 years. The von Bertalanffy growth formulae (VBGF) were expressed as L t ¼ 57:4 1 À e À0:78 tþ0:91 ð Þ À Á for females and L t ¼ 69:5 1 À e À1:07 tþ0:24 ð Þ

The age, growth and maturation of the redbelly tilapia Tilapia zillii introduced into the Haebaru Reservoir on Okinawa-jima Island were studied using 2197 specimens ranging from 7.3 to 168.0 mm standard length (SL). The spawning season was estimated to be from April to August, with a peak in April and May. The first maturation sizes of females and males were estimated to be 38.1 and 33.0 mm SL, respectively. The opaque zones in otoliths that form annually were found to correlate with the spawning season. Maximum ages of females and males were 7 and 6 years, respectively. The von Bertalanffy growth formulae were expressed as: Lt = 99{1 -exp[-0.67(t + 0.09)]} for females and Lt = 155{1 -exp [-0.36(t + 0.12)]} for males. Males grew to be larger than females from the first year onward. Populations of this species are characterized by early maturation life history parameters and are thought to adapt and become established quickly after being released into new water systems. Furthermore, extermination activity in winter is thought to be an effective strategy before the newly recruited fish begin breeding in the warmer months.

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