JOHNSON and HORTON: RATFISH, ASPECTS OF BIOLOGY 



Table 1. — Data to describe length -weight relationship (log weight = log a + 6 log length) for male and female 



ratfish collected off Oregon during 1965-67. 



Location 



Sex 



Sample 

 size 



Constant 

 log a 



Constant 

 b 



Sign. Level of 

 r {P = 0.01)* 



2»» 



Newport 

 Newport 

 Totalt 

 Totalt 



Male 

 Female 

 Male 

 Female 



128 

 56 



175 

 112 



—2.0168 

 —3.1384 

 -4.3217 

 —9.1692 



2.0447 

 2.5336 

 3.0546 

 2.9720 



* From Table X in Quenouille (1952). 

 ** Coefficient of determination (Croxton, 1953). 

 t Composite of collections from Newport, Astoria, Cope Arogo, and Cape Blanco. 



0.9352 

 .9824 

 .9917 

 .9943 



0.234 

 .361 

 .210 

 .257 



0.8746 

 .9651 

 .9835 

 .9886 



weight relationship for male and female ratfish 

 collected off Newport is defined and illustrated 

 in Figure 1. 



A taxonomic list of all food organisms identi- 

 fied from the alimentary canals of 283 ratfish 

 is presented in Table 2. The table also contains 

 lists of the relative importance of food items 

 by the frequency of occurrence and numerical 

 methods (Lagler, 1956) and gives the locations 

 of the collections in which the food items were 

 found. 



Based on these data, ratfish appear to be op- 

 portunistic feeders. The most important food 

 items (>10% occurrence) were shrimp {Pan- 

 dalus and Crago) , mollusks (Mtcsculus and Am- 

 phissa) , and echinoderms (Brisaster) . In gen- 

 eral, young and adult ratfish ate the same foods. 

 Dean (1906) found seaweed in the alimentary 

 canals of ratfish, but we did not find any plant 

 materials in the specimens we examined. 



In the Cape Arago collection, ratfish were 

 eaten by ratfish. One egg capsule and a caudal 

 fin were eaten by two large females (280 mm). 

 We are not aware of any previous record of can- 

 nibalism in ratfish. Of the teleostomi, flatfish 

 appeared to be taken most frequently by ratfish. 

 The two flatfish found were Hippoglossoides 

 elassodon and Esopsetta jordani. 



In the food habits study, we did not use a 

 volumetric method of examination because in 

 many alimentary canals only shells and frag- 

 ments remained. Also, materials such as car- 

 apaces of shrimp have a large surface to volume 

 relationship which causes them to displace little 

 water or to float. Ratfish often void ingested 

 matter between capture and landing, making 

 volumetric measurements inaccurate. Dean 

 (1906) commented on this habit, and we noticed 

 it in ratfish captured by hook and line. In ad- 



3.2 



- 3.0 



I 2 8 



o 



Uj 



*2.6 



>- 



Q 

 O 



(D2 4 

 o 



O 



_1 



2.2 



= FEMALES 



LOG WEIGHT= -3.1384+2.5336 LOG LENGTH 

 r= 9824, r2".965l 



A = MALES 



LOG WEIGHT = -2,0168 +2 0447 LOG LENGTH 

 r=9352, r2=.B746 

 . J I 



2.1 



2.2 2.3 2.4 



LOG BODY LENGTH (S-V) (mm) 



2.5 



Figure 1. — Length -weight relationship of male and fe- 

 male ratfish collected off Newport, Oreg., 1965. 



dition, we found Gyrocotyle in the mouths of 

 some trawl-caught ratfish, indicating that the 

 contents of the alimentary canals recently had 

 been voided. According to Lynch (1945), 

 Gyrocotyle would normally be restricted 

 to the anterior section of the intestine (spiral 

 valve) . 



The parasites found on or in the ratfish were 

 Gyrocotyle urna, G. fimhriata, and the copepod, 

 Acanthochondria sp. Table 3 lists the frequency 

 of Gyrocotyle occurring in the four collections 

 of ratfish. Both G. fimhriata and G. urna ap- 

 peared in about equal numbers in the Newport 

 collection, but only G. fimhriata occurred in the 

 Astoria and Cape Arago collections. The fre- 

 quency of infestation by Gyrocotyle in young 

 fish from the Cape Blanco collection was 30%. 

 We did not find evidence of mass infestation by 

 G?/rocoi^^e, as suggested by Wardle (1932). The 

 young fish (<50 mm) contained from zero to 

 two Gyrocotyle each. The voiding of canal con- 

 tents by the ratfish interfered with obtaining an 

 accurate estimation of the degree of infestation. 



423 



