Editing Perch (section)

=== External anatomy ===
Perch have a long and round body shape which allows for fast swimming in the water. True perch have "rough" or [[ctenoid]] scales. Perch have paired [[Pectoral fin|pectoral]] and [[pelvic fin]]s, and two [[dorsal fin]]s, the first one spiny and the second soft. These two fins can be separate or joined.<ref name=":0">{{Cite journal |last=Weatherley |first=A. H. |date=1963-03-01 |title=A Note on the Head Kidney and Kidney of the Perch Perca Fluviatilis (linnaeus), with Special Reference to the Blood Vascular System |journal=Proceedings of the Zoological Society of London |language=en |volume=140 |issue=2 |pages=161–167 |doi=10.1111/j.1469-7998.1963.tb01859.x |issn=1469-7998}}</ref> The head consists of the [[skull]] (formed from loosely connected bones), [[eye]]s, [[mouth]], [[Operculum (fish)|operculum]], [[gill]]s, and a pair of [[nostril]]s (which has no connection to the oral cavity). They have small brush-like teeth across their [[jaw]]s and on the roof of their mouth. The gills are located under the operculum on both sides of the head and are used to extract oxygen molecules from water and expel carbon dioxide; the gills have [[gill raker]]s inside the mouth.<ref name=":1">{{Cite book |last=Romer |first=Alfred Sherwood |url=https://www.worldcat.org/oclc/3003870 |title=The vertebrate body |date=1977 |publisher=Saunders |others=Thomas S. Parsons |isbn=0-7216-7668-5 |edition=5th |location=Philadelphia |oclc=3003870}}</ref>

External anatomy can be used to determine the [[sex]] of perch in multiple ways. Perch have two posterior openings located on their abdomen, the [[Anus|anal]] and [[Urogenital opening|urogenital]]. In males, the shape of the urogenital opening is round and larger than the anal opening. In females, the urogenital opening is often a V- or U-shape which is a similar size to the anal opening. Also, males usually have a more brown-red colored urogenital opening compared to females.<ref>{{Cite journal |last1=Shepherd |first1= Brian S. |last2=Rees |first2=Christopher B. |last3=Sepulveda-Villet |first3=Osvaldo J. |last4=Palmquist |first4=Debra E. |last5= Binkowski |first5=Fred P. |display-authors= 3| date=May 13, 2013 |title=Identification of Gender in Yellow Perch by External Morphology: Validation in Four Geographic Strains and Effects of Estradiol |url=https://onlinelibrary.wiley.com/doi/10.1080/15222055.2013.783520 |journal= North American Journal of Aquaculture |language=en |volume=75 |issue=3 |pages=361–372 |doi=10.1080/15222055.2013.783520 |issn=1522-2055|url-access=subscription }}</ref>