Francis and Duffy Length at maturity in three pelagic sharks 



491 



spanned the period from 1986 to 2004. In the early 

 years, only data on length, sex, weight, and maturity 

 were collected. In later years, detailed reproductive data 

 were also collected. The following length measurements 

 were made as point-to-point straight line distances to 

 the whole centimeter below actual length: 



Total length (TL nat ): tip of snout to a perpendicular 



dropped from the tip of tail to 

 the midline (with the tail in 

 the natural position); 



Total length (TL flex ): tip of snout to tip of tail (with 



the tail flexed towards the 

 midline to provide maximum 

 extension); 



Fork length (FL): tip of snout to fork in the 



tail; 



Precaudal length (PCL): tip of snout to the upper pre- 



caudal pit (mako and por- 

 beagle sharks) or the origin 

 of the upper caudal lobe (blue 

 sharks). 



Total weight was measured on accurate scales provided 

 at the fishing competitions, on research vessels, or in 

 commercial fish processing sheds. 



In males, inner clasper length was measured between 

 the anterior margin of the cloaca and the posterior clasp- 

 er tip, and expressed as a percentage of fork length: 



Clasper length index (CLI) = 100 (clasper length I FL). 



The degree of clasper calcification and development 

 was determined and included an assessment of whether 

 the terminal cartilages could be splayed open, whether 

 a spur was present and erupted, and whether the en- 

 tire clasper could be rotated. In some males sampled 

 in later years, the degree of development of the testes, 

 epididymis, and ampulla at the posterior end of the 

 epididymis was also recorded, and occasionally testes 

 were weighed and measured (following dissection from 

 the epigonal organ if necessary). The presence or ab- 

 sence of spermatophores or spermatozeugmata in the 

 ampulla epididymis was noted. (Spermatophores are 

 masses of encapsulated sperm, and they are found in 

 porbeagle and mako sharks; spermatozeugmata are 

 unencapsulated masses of naked sperm that are found 

 in blue sharks [Pratt and Tanaka, 1994]). 



In females, the reproductive system was examined, 

 and in later years a number of measurements were 

 taken. Uterus width was measured near the middle of 

 the body cavity and expressed as a percentage of fork 

 length: 



Uterine width index (UWI) = 100 (uterus width/FL). 



sured after dissection (if necessary) from the epigonal 

 organ. Any contents of the uteri were noted; embryos 

 were measured and sex was determined. The presence 

 or absence of a hymen (cloacal membrane occluding the 

 vaginal opening) was recorded. 



For both males and females, a direct assessment of 

 maturity (hereafter called direct maturity) was made 

 by using all the available reproductive data. A three- 

 stage classification scheme was used: immature, ma- 

 turing, and mature. Mature sharks were defined as 

 those in which the reproductive system was judged to 

 be fully functional and capable of delivering reproduc- 

 tive products. For analysis purposes, maturing sharks 

 were grouped with immature sharks. 



Sharks sampled by observers 



Observers sampled tuna longline sets from around the 

 New Zealand region (Fig. 1). Data from blue and mako 

 sharks were obtained throughout the sampled area, but 

 porbeagles came mainly from the southwestern South 

 Island. Most sharks were sampled in autumn-winter 

 (April-July) over the period 2001-2003. The "standard" 

 length measurement for sharks was FL, but frequently 

 observers also recorded TL nat or PCL. 



Observers were provided with instructions and pho- 

 tographs indicating the reproductive data they needed 

 to collect, but they were not provided with any practi- 

 cal training. The main data they collected were the 

 following: inner clasper lengths, presence or absence of 

 spermatophores or spermatozeugmata in the ampulla 

 epididymis (for males); uterus width, maximum ovum 

 diameter, and whether the shark was pregnant or not 

 (for females). 



Examination of observer pregnancy records for blue 

 sharks indicated numerous probable errors: uterus 

 widths from sharks scored as pregnant were frequently 

 less than 18 mm, which seems implausible considering 

 that ova are ovulated at about 18 mm, and pregnant 

 sharks are unlikely to have such small uteri (Pratt, 

 1979; Natanson 1 ). This problem was apparent for sev- 

 eral observers, some of whom were very experienced 

 (although they had no previous experience examining 

 shark reproductive systems). We suspect that they may 

 have scored some female blue sharks as pregnant if the 

 ovary contained large yolky ova (this problem did not 

 occur for mako and porbeagle sharks, which have much 

 smaller ovarian ova). We therefore used observer blue 

 shark pregnancy records only if they were supported by 

 appropriate comments on the data sheet (e.g., mention 

 of embryos or ovulated eggs in uteri), or if the observers 

 retained embryos or intact uteri for us to examine. 



Observers did not assess direct maturity; therefore 

 we were unable to derive direct maturity ogives for 

 observer sharks. 



The maximum diameter of ova, where they were suf- 

 ficiently developed to be visible in the ovary, was re- 

 corded, and the diameter of the oviducal gland was 

 measured. Ovarian dimensions and weight were mea- 



1 Natanson, L. 2004. Unpubl. data. National Marine Fish- 

 eries Service, 28 Tarzwell Drive, Narragansett, Rhode Island 

 02882-1152. 



