85* 



80* 



75° 



70° 



65* 



60* 



55* 



* y j ■ 1 1 ■ ■ rriTrn ■ ■ i ■ ■ rmm ■ ■ i ■ ■ rrnrr t ■ ■ i ■ ■ rrnrn ■ ■ 1 1 1 rrnrn n i n i n i n i n i n rr rtTTi iitniiiiTitiitiiintninii iTi ■ 1 1 ■ I n t ■■ rnTin ni niniiiininininintn fiTtrn nininin ItHtt4tt^ 



"'Minim n 



50° 

 N. 



0° 



| IIIMtlMMI Mill) IIMIIIIIMirillMI Ml Ml MIIM MjmilllllMjmMlllimMIMIIIIIIIMJMIIMIMIII MIIIMMIMIMIM "_'»_" IMIMIMIIIMIIMMIMIIUIM IM Ml . | 



85' 80° 75° 70° 65° 60° 55°W 



Figure 2. — Localities of collection of skipjack tuna ovaries in the western tropical Atlantic. 



50° 



the BCF Tropical Atlantic Biological Labo- 

 ratory, where the fork length and weight of 

 each fish were recorded, and stomachs and 

 gonads were preserved in Formalin. 



Off New York, specimens were collected in 

 August 1965 and 1966 by the commercial fish- 

 ing vessels Puritan , Lexington , City of Tacoma , 

 and Chicken of the Sea ; they were landed (and 

 sampled) in Puerto Rico. After the lengths of 

 these fish were recorded, the stomachs and 

 gonads were removed, preserved in Formalin, 

 and shipped to me. Ovaries from 90 fish were 

 obtained from these ships (table 1). 



The ovaries were divided into the five de- 

 velopmental stages shown below. Stages 1 to 3 

 were modified from Yoshida (1965) and stages 

 4 and 5 were modified from Schaefer and 

 Orange (1956). 



1. E arly developing stage --Ova appear in 

 all ovaries as simple transparent cells; the 

 large ova contain a relatively large nucleus. 



2. Developing stage--Ova are completely 



opaque because of the deposition of yolk 

 granules. 



3. Advanced stage --Ovaries range in de- 

 velopment from those with ova still relatively 

 opaque, containing a cluster of small oil 

 droplets, to those with semitransparent ova 

 containing a well-developed, bright yellow oil 

 globule. 



4. Ripe stage--Ova are translucent and 

 loose in the lumen of the ovary; they may be 

 extruded from the fish by external pressure 

 on the abdomen. (No ripe specimens were 

 found in the present study.) 



5. Spawned stage- -Remnants of ripe ova 

 remain in the lumen or among the folds of the 

 ovary, and are discovered only through micro- 

 scopic examination. Ovaries in this stage are 

 frequently enlarged, hollow, and flaccid. Ex- 

 cept for the remnants of mature ova, the ovaries 

 may be identical with those in stages 1, 2, or 3. 



I assumed that skipjack tuna in the develop- 

 ing stage were nearing spawning condition and 



