538 



Abstract — The lack of information 

 concerning the preservation of ovar- 

 ian material of fish species inhib- 

 its standardization of methods for 

 determining fecundity and measur- 

 ing oocytes. The effects of four pre- 

 servatives (10'5f phosphate-buffered 

 formalin, modified Gilson's solution, 

 70% ethanol, and freezing) on ovarian 

 material weight and oocyte size were 

 quantified for prespawning Atlantic 

 cod {Gadus morhua), haddock (Mela- 

 nogrammus aeglefinus), and American 

 plaice iHippoglossoides platessoides). 

 Effects of preservation were similar 

 between Atlantic cod and haddock 

 but different between Atlantic cod 

 and American plaice for nearly all 

 comparisons. Although all treatments 

 affected the weight of ovarian mate- 

 rial, freezing caused the most change 

 and formalin caused the least. Such 

 significant species-specific effects 

 should be quantified in the calcula- 

 tion of life history characteristics, 

 such as fecundity, to minimize error. 

 This is one of few studies dedicated 

 to evaluating the effects of preserva- 

 tion on oocytes and ovarian material 

 and is the first to evaluate multiple 

 preservatives on species. 



Species-specific effects of four preservative 

 treatments on oocytes and ovarian material of 

 Atlantic cod (Gadus morhua), 

 haddock iMeianogrammus aeglefinus), and 

 American plaice iHippoglossoides platessoides) 



Nikolai Klibansl<y 



Francis Juanes (contact autlior) 



Email address for F. Juanes: |uanesi®forwild. umass.edu 



Department of Natural Resources Conservation 

 University of Massachusetts 

 160 Holdsworth Way 

 Amherst, Massachusetts 01003 



Manuscript submitted 17 October 2006 

 to the Scientific Editor's Office. 



Manuscript approved for publication 

 5 July 2007 by the Scientific Editor. 



Fish. Bull. 105:538-547 (2007). 



Because of the weak relationship be- 

 tween spawning stock biomass and 

 stock reproductive potential (Marshall 

 et al., 1998, 2003), stock assessment 

 scientists recommend incorporating 

 basic reproductive biology (such as 

 fecundity) into estimates of stock 

 reproductive potential. Estimating 

 fecundity and other reproductive 

 biological parameters often requires 

 oocytes or ovarian material, preserved 

 chemically or by freezing. Ovaries 

 can sometimes be weighed fresh, 

 but often, as when they are collected 

 aboard ships where special marine 

 scales are not available, they must 

 be preserved until they are weighed 

 in the laboratory. 



Common preservatives can affect 

 the size and weight of oocytes differ- 

 ently among species. Formalin can 

 increase the mean diameter of catfish 

 eggs by 4-11% (Tan-Fermin, 1991), 

 and the mean diameter of cod eggs 

 by 3.5% (Svaasand et al., 1996), but 

 does not affect the weight of salmon 

 eggs (Fleming and Ng, 1987). Com- 

 mon preservatives have also been 

 shown to affect oocyte size of the 

 same species differently in different 

 studies. Schaefer and Orange (1956) 

 found that standard Gilson's solution 

 and formalin had the same effect on 

 oocyte diameter of yellowfin (Neot- 

 hunnus macropterus) and skipjack 

 {Katsuwoniis pelamis). In contrast, 

 Joseph (1963) found the mean diam- 

 eter of oocytes of these same tuna 



species preserved in standard Gilson's 

 solution to be 24% smaller than the 

 mean diameter of oocytes preserved 

 in formalin. 



To enable accurate comparisons of 

 fecundity information among popula- 

 tions and years, data should be col- 

 lected and analyzed by a standard 

 method and a standard preservative 

 should be used for storing oocytes 

 and ovarian material. But because 

 little research has been conducted 

 on the effects of preservatives on 

 oocyte size, the selection of a pre- 

 servative is usually based more on 

 popular use than empirical knowl- 

 edge — a process that may perpetu- 

 ate the use of inferior preservatives 

 and unnecessary toxins. Preserva- 

 tives that have been used in past 

 fecundity research may be adequate 

 for determining fecundity but may 

 not preserve ovarian material well 

 enough for related analyses, particu- 

 larly histology. 



The three most commonly em- 

 ployed chemical treatments for ovar- 

 ian material are 10% buffered for- 

 malin (3.7% formaldehyde), standard 

 Gilson's solution, and freezing. For- 

 malin and freezing are best used for 

 short-term preservation (up to two 

 years) of ovarian material; however, 

 formalin is ideally employed as a fixa- 

 tive. Standard Gilson's solution also 

 preserves ovarian material but was 

 developed to dissolve the interstitial 

 material that holds oocytes together 



