Length correction for early-juvenile Brazilian herring Sardinella janeiro (Eigenmann, 1894) after preservation in formalin, ethanol and freezing

Abstract

This work aims to quantify the variation in total length and body mass for the early-juvenile Brazilian herring Sardinella janeiro and to determine total length and body mass correction equation to allow fresh measures to be calculated from preserved ones. Fishes were randomly assigned to one of five preservation methods (freezing at -20° C, 2.5% and 5% formalin, 70% and 95% ethanol), and measured for total length (TL) and body mass (W) before preservation, and on days 5, 15, 30, and 60 after storage. Significant reductions in total length and body mass occurred during the first 5 days after preservation and continued to contract significantly at a lesser rate through 30 days in most methods. Exceptions were shown for body mass in freezing and 5% formalin, where the greatest losses occurred after 30 days of preservation. The degree of shrinkage for total length and body mass was very much dependent on fish size, with smaller specimens shrinking more than larger ones. The fresh total length and body mass can be back-calculated using equations that describe the relationship between fresh and preserved individuals after 60 days storage for all methods except for body mass in freezing.Este trabalho objetivou quantificar a variação do comprimento total e massa corporal para pós-larvas de Sardinella janeiro e determinar as equações de correção para o cálculo do comprimento total e da massa corporal a partir de espécimes preservados. Os peixes foram submetidos aleatoriamente a cinco métodos de preservação (congelamento -20° C, formalina 2,5% e 5%, álcool 70% e 95%), e medidos o comprimento total (CT) e pesado a massa corporal (P) antes da preservação, e 5, 15, 30 e 60 dias após a preservação. Foram observadas perdas significantes no comprimento total e na massa corporal durante os cinco primeiro dias após a preservação, prosseguindo em menor intensidade até o 30º dia na maioria dos métodos. Exceções foram observadas para a massa corporal em congelamento e formalina 5%, com perdas ocorrendo mesmo depois de 30 dias de preservação. O grau de perdas para comprimento total e massa corporal foi significativamente dependente do tamanho dos peixes, com os menores indivíduos sofrendo as maiores perdas. O comprimento total e massa corporal de indivíduos frescos podem ser retro-calculados usando equações que descrevem a relação entre indivíduos frescos e após 60 dias de preservação para a maioria dos métodos, exceto para a massa corporal em congelamento.

Correction of the weight and length for juveniles Atherinella brasiliensis (Actinopterygii: Atherinopsidae) after fixation in formalin and preservation in ethanol

“…Conversion factors using complete equations are necessary to correct the weight and length of specimens in the present study. Our finding are corroborated by SANTOS et al (2009) who proposed correction factor using complete equations for Sardinella janeiro (Eigenmann, 1894). …”

“…Despite its usefulness in keeping specimens preserved for future analysis, this method can alter the weight and length of the subjects (ARMSTRONG & STEWART 1997, KRISTOFFERSEN & SALVANES 1998, SANTOS et al 2009). …”

“…Variables obtained from the latter can be misleading (PORTER et al 2001, SANTOS et al 2005. In attempting to correct variations in weight and length that result from preservation techniques, several studies have suggested a correction factor to estimate the initial weight and total length of specimens using appropriate equations (BUCHHEISTER & WILSON 2005, FEY & HARE 2005, SANTOS et al 2009). However, the calculations of weight and total length losses proposed in the literature are generally limited to the effects of either fixation (in formalin) or preservation (in ethanol).…”

The Influence of Preservation on Fish Morphology in Museum Collections Based on Two Species of the Genus <I>Lepomis</I> (Actinopterygii: Perciformes: Centrarchidae)

“…Historically, formalin was used as a fixative and preservative; however, more recently this method changed given the toxicity of formalin (Morgan 1997) to using formalin for fixation and ethyl alcohol for preservation (Kelsch andShields 1996, Al-Hassan et al 2000). Regardless of the technique, the effects of preservation can be species-and size specific (Ehrlich 1974, Hjörleifsson and Klein-MacPhee 1992, Al-Hassan et al 2000, Cunningham et al 2000, Jawad 2003, Santos et al 2009, Lee et al 2011 or vary with the type of preservation (Cunningham et al 2000, Jawad 2003, Santos et al 2009). …”

“…Regardless of the technique, the effects of preservation can be species-and size specific (Ehrlich 1974, Hjörleifsson and Klein-MacPhee 1992, Al-Hassan et al 2000, Cunningham et al 2000, Jawad 2003, Santos et al 2009, Lee et al 2011 or vary with the type of preservation (Cunningham et al 2000, Jawad 2003, Santos et al 2009). …”