349 
Abstract .-Seventy-five shovelnose 
guitarfish, Rhinobatos productus, were 
collected between November 1988 and 
January 1991 near Long Beach, Cali- 
fornia, to determine age, growth, and 
sexual maturity. Thirteen guitarfish 
were kept in captivity and injected with 
Terramycin to provide a time mark for 
growth analysis. Later, vertebral cen- 
tra were examined for opaque band for- 
mation, and there were positive results 
in two individuals. Outer margin analy- 
sis of centra from captive and field-col- 
lected guitarfish indicated that opaque 
bands formed between August and De- 
cember. Guitarfish were aged to 11 
years, and growth appeared to be best 
represented by a linear growth equa- 
tion, TL = 43.33 + 6.90.x, where TL = 
total length and x = estimated age in 
years. Analysis of reproductive tracts 
showed that female guitarfish matured 
at 99 cm (estimated age at seven years). 
Clasper length and width indicated 
that males matured at 90-100 cm (es- 
timated age at eight years). 
Manuscript accepted 5 October 1996. 
Fishery Bulletin 95:349-359 (1997). 
Age, growth, and sexual maturity of 
shovelnose guitarfish, Rhinobatos 
productus (Ayres) 
Maryellen Timmons* 
Richard N. Bray** 
California State University Long Beach 
Long Beach, California 90840 
*Present address: Marine Extension, University of Georgia 
30 Ocean Science Circle, Savannah, Georgia 3141! 
** Present address Department of Biology 
California State University San Marcos 
San Marcos, California 92096 
E-mail address (for Maryellen Timmons): mare@uga.cc.uga.edu 
Recently, a Federal fishery manage- 
ment plan was initiated for some 
large coastal and pelagic species of 
sharks of the eastern seaboard of 
the United States (NMFS 1 ). Regu- 
lations on shark fisheries are impor- 
tant not only because they affect 
fisheries but because they set an 
example to be followed by other 
coastal areas. Many species of elas- 
mobranchs are highly migratory; 
thus regulations are necessary on 
a broader scale if they are to be ef- 
fective management tools. 
Elasmobranchs tend to have slow 
growth and low fecundity (Holden, 
1973); thus, overexploitation of a 
species is possible. Fortunately, re- 
cent collection of age, growth, and 
reproductive data on elasmobranchs 
has helped provide some of the 
baseline information necessary to 
manage many species. 
The shovelnose guitarfish, Rhino- 
batos productus , is a common 
coastal ray found in temperate wa- 
ters along the Pacific coast of the 
United States from Baja California 
to San Francisco (Miller and Lea, 
1972). Although not a highly prized 
commercial catch, it is edible and 
is often found in fish markets la- 
beled as generic “shark steak” and 
sold on piers in Santa Barbara, Cali- 
fornia, as “fish n’ chips.” Guitarfish 
is not sold as “guitarfish” on restau- 
rant menus; however it may become 
a popular fare in the future as a 
substitute for shark. Furthermore, 
dried guitarfish are sold in large 
numbers as curios in shell shops 
from central California to Baja Cali- 
fornia. The majority of guitarfish 
sold for human consumption are the 
larger, mature individuals; how- 
ever, curio and shell shops tend to 
sell all sizes, especially newborn 
pups. Congeners of Rh inobatos are 
particularly targeted for commer- 
cial sale in other areas of the world 
including Peru (Tresierra et al., 
1989) and Brazil (Lessa and Vooren, 
1986). Currently, in southern Cali- 
fornia, commercial landings of gui- 
tarfish are grouped under benthic 
shark species and not recorded as 
guitarfish. 2 Most literature on R. 
productus is contained in field 
guides and California Fish and 
Game publications (Roedel, 1953; 
Miller and Lea, 1972; Lane and Hill, 
1975; Eschmeyer et al. 1983; Tal- 
ent, 1982, 1985) usually with no 
more than brief mention of some of 
1 NMFS. 1993. Fishery management 
plan for sharks of the Atlantic Ocean. 
Prepared for the U.S. Dep. Commer., Natl. 
Mar. Fish. Serv., NOAA, 167 p. 
2 Vojkovich, M. 1994. Dep. Fish and Game, 
Long Beach, C A 90807 . Personal commun . 
