Preserving young-of-the-yearPerca fluviatilisin ethanol, formalin, or in a frozen state and the consequences for measuring morphometrics

Abstract

As it is often not possible to immediately analyse individuals sampled in the field, captured fish are preserved and stored for later investigation. The objective of this study was to assess the effects of various preservation methods on subsequent changes in morphometric parameters while also providing correction factors to re-calculate the original body dimensions when sampled fish are measured at a later date. In this study, juvenile perch (Perca fluviatilis, 66.5 ± 10.2 mm total length) were measured directly after capture, then either frozen at )20°C, preserved in 70% ethanol, or in 4% formalin. They were again measured after 24 h, 3 days, 7 days, and thereafter on a weekly basis for 8 weeks. Ethanol-preserved perch greatly decreased length and weight; formalin preservation also led to a comparable length reduction, but increased the weight of the perch. In contrast, frozen perch showed less shrinkage and only moderate weight loss. Of the three preservation methods, freezing clearly caused the fewest distortions. Hence, freezing is recommend as the most preferable preservation method, especially in multi-disciplinary studies on fish ecology; for all other preservation methods the correction factor over time will have to be pre-determined for each species and size class.

Evaluating Ethanol-based Sample Preservation to Facilitate Use of DNA Barcoding in Routine Freshwater Biomonitoring Programs Using Benthic Macroinvertebrates

“…Traditionally, formalin has been used to preserve marine benthos [11]. Formalin preservation acts by fixing proteins through binding to peptide linkages, which preserves morphological structure but also acts to degrade DNA [12]–[13] Ethanol is the most common preservative for freshwater biomonitoring programs [14], [15].…”

Effects of freezing on white perch Morone americana (Gmelin, 1789): implications for multivariate morphometrics

“…measurements taken immediately after capture). König and Borcherding () reported that whole‐body morphology of frozen fish differed the least from fresh fish, and that most changes occurred within a few days of preservation in all methods. Although much higher than for other methods, the reported P‐value for manova of Canonical Variate Analysis scores used to assess changes in whole‐body morphology was still significant after 54 days frozen, demonstrating changes in overall morphology induced by freezing.…”

“…Although much higher than for other methods, the reported P‐value for manova of Canonical Variate Analysis scores used to assess changes in whole‐body morphology was still significant after 54 days frozen, demonstrating changes in overall morphology induced by freezing. König and Borcherding () ultimately concluded freezing should be a ‘standard preservation technique for fish intended for morphometric analysis (p. 743).’…”

“…Effects of freezing on whole body morphometrics of age‐1 white perch ( Morone americana ) from Lake Erie were examined. The objectives were to determine if duration of freezing affects whole‐body morphometrics for this species and to expand the results of König and Borcherding () to inform the practice of freezing of fish for morphometric analyses.…”

The Central Nervous System of Jawless Vertebrates: Encephalization in Lampreys and Hagfishes

“…The combined data set contained measurements of brain and body mass made on both fresh tissue and formalin-fixed samples, using a range of preservation and storage methods (ethanol, formalin, or phosphate buffer), some of which had been stored in 70% ethanol for up to 65 years. Most studies on the effects of fixation and preservation on aquatic vertebrates have shown that both body mass and length undergo significant changes following fixation and storage in various media [Shields and Carlson, 1996;Kristoffersen and Salvanes, 1998;Buchheister and Wilson, 2005;König and Borcherding, 2012]. This applies to both larval and adult lampreys, in which differences of 3-6% have been recorded between fixed and fresh tissues [Stähler, 1982;Neave et al, 2006].…”