Male Freshwater Fish With Female Features

The reduction of a multiple page journal article such as Jo Ellen Hinck’s, Widespread occurrence of intersex black basses (Micropterus spp.) from U.S. Rivers, 1995-2004, into a few hundred word newspaper article will naturally require some simplification. However, many aspects of the article Male Bass Found With Female Features in the US are very misleading.
To begin with, the newspaper article is lacking in a specific definition of what classifies a fish as intersex. This definition is required so that the true severity of the condition can be realized. The normal fisherman will not be able to catch a fish and find dual reproductive organs, because the fish in this study were analyzed at a microscopic level. To be classified as intersex, the germ cells must be mixed, but this is only detectable under a microscope. (Hinck, 2009)
The first way that data was reported inaccurately was through the misuse of percentages. The journal article specifically states that, “overall, only 97 of 3110 fish (3%) were intersex” (Hinck, 2009) of the total number of fish tested were intersex. This seems like a fairly small amount, but it becomes inflated to 6% in the newspaper by only considering the male fish tested. Only one female fish was found to be intersex, so by using the male statistic, the article makes the problem out to be worse than it is. Nothing is mentioned about the frequency of female intersex, so the reader assumes it to be comparable with the male which is not the case.
The second instance of poor data representation is the newspaper’s estimate of 77% affected small mouth bass. This is one of the highest results obtained. Only the areas that show a high frequency of affected fish are mentioned in the newspaper, giving an overall impression of a worse problem than it actually is. Other river basins yielded far more unaffected fish or even none at all. Again, the reader reads these chosen statistics and receives a general impression inconsistent with what was actually found in the study.
Another dissimilarity comes with the discussion of why male fish are becoming feminine. The newspaper states that this is a “problem linked to women's birth control pills and other hormone treatments that seep into rivers.” (Associated Press, 2009) Although it is true that hormone leaching may attribute to deformities in male fish it is not the only cause. The newspaper focuses on this one factor, leading the reader to believe that it is the only factor. In fact, “The mechanism or mechanisms responsible for intersex is not known, but many factors including exogenous steroids, temperature, pH, behavioural cues, and pollutants can influence sex differentiation in fish” (Hinck, 2009). There are varieties of ways these fish may have been altered, so it is misrepresentative to center out human use of hormones as the main cause. Our freshwater fish populations are currently being exposed to many unnatural variations, making a simple one cause, one effect relationship impossible. This study did not even attempt to determine the reason why freshwater fish are becoming intersex, so it is unreasonable to propose a cause based on Hinck’s research.
Finally, the limitations of this study are not mentioned at all in the newspaper. All numbers are given with perfect confidence, and presented as though they represent fish populations of America completely. In the journal article, it states, “Our sampling methodology did not allow us to determine the true prevalence or severity of intersex in the fish species collected and is therefore not adequate to estimate or quantify a baseline occurrence in these species.” (Hinck, 2009) It is concluded that a general percentage can not be put on the whole of freshwater fish stocks in the United States based solely on this one study. Further reading proves that in fact only a sampling was made of the whole of the fish population. Three thousand, one hundred and ten fish seem like a large sample size, however this was spread across 111 locations in 9 river basins. For the whole of United States , this is small representation. In the end, only a handful of fish were caught in any one location, and the study only truly represents those nine rivers studied.
In general, the claims made by the newspaper were far more confident and widely applied than is accurate. The primary source made a tentative claim that the frequency of intersex in freshwater fish is increasing. Hinck ensured that the readers understood the limitations to the research done and the variables that still need to be tested. The newspaper was written to keep readers interested, but didn’t provide entirely accurate data.
So, are the United State ’s freshwater fish stocks in trouble? Possibly…but more research is required to prove an increase in intersex levels, and entirely new studies are needed to determine the exact cause.

- Amy Adair

References

Associated Press. (2009) Male Bass with Female Features Found in U.S. CBCnews, 15 September 2009. http://www.cbc.ca/technology/story/2009/09/15/tech-biology-fish-sex-organs.html. Accessed 3 October 2009.

Hinck, Jo Ellen; Vicki S. Blazer; Christopher J. Schmitt; Diana M. Papoulias, Donald E. Tillitt. (2009)
Widespread occurrence of intersex black basses (Micropterus spp.) from U.S. Rivers, 1995-2004, Aquatic Toxicology, 13 August 2009. doi:10.1016/j.aquatox.2009.08.001 http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6T4G-4X0F3NH-1&_user=1067211&_coverDate=08%2F13%2F2009&_alid=1034098544&_rdoc=1&_fmt=high&_orig=search&_cdi=4974&_docanchor=&view=c&_ct=1&_acct=C000051237&_version=1&_urlVersion=0&_userid=1067211&md5=001849bd93b277963a97c8b34adf8101 Accessed 4 October 2009.