Non-linear curve adjustments widen biological interpretation of relative growth analyses of the clam Tivela mactroides (Bivalvia, Veneridae)

Abstract

Evaluation of relative (allometric) growth provides useful information to understand the development of organisms, as well as to aid in the management of fishery-exploited species. Usually, relative growth analyses use classical models such as the linear equation or the power function (allometric equation). However, these methods do not consider discontinuities in growth and may mask important biological information. As an alternative to overcome poor results and misleading interpretations, recent studies have suggested the use of more complex models, such as non-linear regressions, in conjunction with a model selection approach. Here, we tested differences in the performance of diverse models (simple linear regression, power function, and polynomial models) to assess the relative growth of the trigonal clam Tivela mactroides, an important fishing resource along the South American coast. Regressions were employed to relate parameters of the shell (length (L), width (W), height (H) and weight (SW)) among each other and with soft parts of the organism (dry weight (DW) and ash-free dry weight (ASDW)). Then, model selection was performed using the information theory and multi-model inference approach. The power function was more suitable to describe the relationships involving shell parameters and soft parts weight parameters (i.e., L vs. SW, DW, and AFDW, and SW vs. DW). However, it failed in unveiling changes in the morphometric relationships between shell parameters (i.e., L vs. W and H; W vs. H) over time, which were better described by polynomial functions. Linear models, in turn, were not selected for any relationship. Overall, our results show that more complex models (in this study polynomial functions) can unveil changes in growth related to modifications in environmental features or physiology. Therefore, we suggest that classical and more complex models should be combined in future studies of allometric growth of molluscs.

Length – Weight Relationship of Bivalves and Gastropods from Mangrove Forest of Brgy. Nabago, Surigao City, Philippines

“…The positive allometric pattern (b > 3) considering the total length and total weight of A. edentula conforms to the findings in the study of Degamon and Gamalinda Turra et al, (2018), Elvira and Jumawan (2017), Ramesha and Sophia (2015), Miley et al, (2012) and on the study of Park and Oh (2002). According to Perez and Santelli (2018), this growth pattern is typical to infaunal burrowing bivalves.…”

“…It has to be noted that whatever growth patterns these bivalves have, there are several factors influencing them. Their growth and morphometry may be affected by both environmental factors such as current, depth, temperature, wave exposure, and sediment and biological factors like predation and burrowing abilities (Gaspar et al, 2002;Gimin et al, 2004;Babei et al, 2010 andTurra et al, 2018).…”

Pea Crab Distribution and Its Morphological Characteristics Studied in Bivalves From Setiu Wetlands, Terengganu

“…The pea crab only found in the mud clam with a mean number of 0.3. (Turra et al, 2018). In the dry season, a total number of pea crab isolated from fifty samples of each bivalve was 13 and 10 remain unidentified small crab isolated from the oyster.…”

Variação morfométrica de Tivela mactroides (Bivalvia, Veneridae) no litoral Norte-Nordeste do Brasil

“…Através da análise da morfologia da concha de T. mactroides, obtêm-se informações que auxiliam no entendimento da história de vida de T. mactroides, bem como, implicações para a sua exploração econômica como recursos pesqueiros (Turra et al, 2018). Adicionalmente, permite estimar a produção e a biomassa de uma população a partir de um único parâmetro, como comprimento ou largura, podendo servir de ferramenta de apoio na exploração e manejo de espécies colhidas, por exemplo, atuando na melhora da seletividade de tamanho das artes de pesca (Vasconcelos et al, 2018).…”

“…Vários estudos têm sido realizados sobre Tivela mactroides no Brasil envolvendo a morfologia (Denadai et al, 2006), distribuição (Denadai et al, 2005;Medeiros et al, 2014;Rocha & Matthews-Cascon, 2015), dinâmica populacional (Denadai et al, 2015c), crescimento relativo (Turra et al, 2018), aspectos ecológicos (Turra et al, 2014), incluindo análise de predação multiespecífica (Turra et al, 2015; Batalla 2017), mortalidade (Turra et al, 2016a) e reprodução de indivíduos (Denadai et al, 2015b), bem como pesquisas voltadas para a pesca (Denadai et al, 2015a) e aspectos socioeconômicos (Turra et al, 2016b).…”