Post mortem shrinkage of four species of temperate and tropical marine fishes, without freezing or preservation

Abstract

The present study indicated significant post mortem decreases in length for four Australian teleost species from temperate to tropical habitats: black bream Acanthopagrus butcheri, King George whiting Sillaginodes punctata, summer whiting Sillago ciliata and redthroat emperor Lethrinus miniatus. Shrinkage averaged 5·0 mm after 24 h (range 0–10 mm) for A. butcheri, 4 mm (0–8 mm) for S. punctata, 2·2 mm (0·7–3·7 mm) for S. ciliata and 5·4 mm (−2·5–15·0 mm) for L. miniatus. For A. butcheri held under three different post mortem treatments, the mean length of fish in all treatments decreased but there was no significant effect of treatment type on the extent of shrinkage. The rate of shrinkage of S. ciliata varied with treatment, but the ultimate extent did not. For A. butcheri shrinkage was most rapid (2·5 mm h−1) between 1 and 2 h postcapture. The results from these studies confirm that a post mortem decrease in length is a common phenomenon, even in fishes that are not frozen or preserved. Such shrinkage has implications for the enforcement of minimum legal length legislation, and may cause bias in biological investigations, including growth estimates from tag and recapture studies.

Preservation causes shrinkage in seahorses: implications for biological studies and for managing sustainable trade with minimum size limits

“…The proportion of seahorses Z10 cm at capture that would be expected to shrink below the MSL due to desiccation (as in Morison et al, 2003) was calculated using the size frequency of seahorse bycatch reported for three seahorse species, H. guttulatus (Curtis and Vincent, 2006), H. hippocampus (Curtis, 2004; J Curtis, unpublished data) and H. erectus (Baum et al, 2003). Catch data for H. guttulatus (n 5 2733) and H. hippocampus (n 5 281) were obtained from thawed seahorses captured during an unrelated study (Erzini et al, 2002) and height was measured as a straight line (Curtis, 2004;Curtis and Vincent, 2006).…”

“…Despite a rich body of literature that documents the shrinking effects of mortality and preservation on the body lengths of fishes (Hay, 1982;Fowler and Smith, 1983;Leslie and Moore, 1986;Kruse and Dalley, 1990;DiStefano et al, 1994;Fisher et al, 1998;Morison et al, 2003), few studies have investigated the implications of shrinkage for the enforcement of size limits (Mapstone et al, 2004). Minimum size limits (MSLs) are widely applied as tools for regulating recreational and commercial fisheries (Perry et al, 2002;Morison et al, 2003;Mapstone et al, 2004).…”

“…If seahorses shrink, as do other fish when preserved, the enforcement of the generic 10 cm MSL could pose some challenges at the point of trade. For example, fish of legal size falling above a MSL at capture may, within hours, shrink to below the size limit (even prior to preservation), leading to uncertainty in how the MSL should be enforced (Morison et al, 2003;Mapstone et al, 2004). Potential consequences for seahorse trade include wasteful retention of captured animals that may not be exported under CITES recommendations (shrunk below 10 cm MSL prior to export), and economic losses for seahorse fishers (Salin et al, 2005).…”

“…Minimum size limits (MSLs) are widely applied as tools for regulating recreational and commercial fisheries (Perry et al, 2002;Morison et al, 2003;Mapstone et al, 2004). Where complex population assessments are hindered by a scarcity of biological information, MSLs can be established using biological reference points (e.g.…”

“…Morphometric measurements are used in taxonomic studies and fisheries science to identify species, estimate life history parameters, and set fishing regulations (Fowler and Smith, 1983;Binohlan, 2000, 2003;Morison et al, 2003;Smith and Walker, 2003). For morphometrics to be maximally useful, measurement errors and other biases must be accounted for in length estimates and eliminated where possible (Theilacker, 1980).…”