FISHERY BULLETIN: VOL. 87, NO. 1 



35°N) from May 1983 through January 1987. 

 "Adult" (= age >0) fish were caught on hook and 

 line in the recreational fishery, in the commercial 

 fishery, and during research cruises aboard the RV 

 Oregon and RV Lady Lisa. Most YOY kings were 

 collected during research cruises aboard the RV 

 Lady Lisa and RV Carolina Pride using trawls of 

 various types, but some fish were taken with gill 

 nets, seines, and from commercial shrimp trawling 

 bycatch. Larvae were collected from the RV Oregon 

 with bongo (505 j^m mesh) and neuston (505 or 947 

 ^im mesh) nets, and were preserved in 95% ethanol. 



Nonlarval king mackerel were weighed and mea- 

 sured (total length [TL] and fork length [FL]), while 

 larvae were measured to the nearest mm standard 

 length (SL) using a dissecting microscope and ocular 

 micrometer. Sagittae of adults were removed and 

 stored dry, and gutted fish and gonads were 

 weighed when possible. All otoliths were removed 

 from larval and YOY fish. Larval otoliths were 

 mounted on microscope slides, while otoliths from 

 YOY fish were stored in 75% ethanol. 



The lapillus was the best structure from which to 

 count presumed daily rings for both larval and YOY 

 king mackerel.^ Larval lapilli were immersed in oil 

 on a microscope slide and viewed with transmitted 

 light at 623 x on a microscope equipped with a video 

 camera. Two readers made three counts for each 

 of 29 larvae (2-7 mm SL), and the mean of the six 

 counts, rounded to the nearest integer, was used to 

 estimate the number of presumed daily rings. Lapilli 

 from 69 YOY fish (79-320 mm FL) were prepared 

 by a series of polishings on a smooth whetstone, on 

 600 grit sandpaper, and on glass with a fine liquid 

 abrasive (AO Scientific Instruments Cat. No. 938C^). 

 Polishing continued until rings in the central por- 

 tion of the lapillus became visible, and readings were 

 made in the same manner as those for larvae. Some 

 lapilli were also read from photomicrographs taken 

 with a scanning electron microscope (SEM) to deter- 

 mine differences in marginal increments (distance 

 from the distal edge of the outer ring to the otolith 

 margin) between fish caught at different times of 

 day. 



Whole sagittae from 683 adult fish were ex- 

 amined. Otoliths were placed in a dish of cedarwood 



^Waltz, C. W. 1986. Evaluation of a technique for estimating 

 age of young-of-the-year king (Scomheromorus cavalla) and Span- 

 ish (S. maculatus) mackerels. Unpubl. manuscr. South Caro- 

 lina Wildlife and Marine Resources Department, Marine Re- 

 sources Research Institute, P.O. Box 12559, Charleston, SC 

 29412. 



^Reference to trade names does not imply endorsement by the 

 National Marine Fisheries Service, NOAA. 



oil and viewed, concave side up, under a dissecting 

 microscope (12 x) with reflected light. Measure- 

 ments from the focus to the distal edge of each 

 opaque ring, and from the distal edge of the last 

 opaque ring to the otolith margin, were made with 

 an ocular micrometer along an axis approximating 

 the extension of the sulcus acousticus (Johnson et 

 al. 1983). The marginal increment was zero when 

 an opaque ring occurred at the otolith margin. 

 Transverse sections (ca. 0.5 mm thick) of one sagit- 

 ta from each of 773 fish, including otoliths also read 

 whole, were made through the focus on a plane 

 perpendicular to the long axis with a Buehler Isomet 

 low speed saw. Sections were viewed at 50 x in the 

 same manner as whole sagittae. The focus was not 

 always definite on sections, so measurements were 

 standardized by defining the focus as the midpoint 

 of a line connecting the two most distant points of 

 the first ring. This convention closely agreed with 

 actual focus locations for sections in which the focus 

 was apparent. Because the axis of sagittal growth 

 changed after the first year, sections were measured 

 in two parts: 1) from the focus to that point on the 

 first ring, on the dorsal side of the sulcus acousticus, 

 which minimized the length of the line without cross- 

 ing the sulcus acousticus, and 2) from the first ring 

 to the margin of the section, on a line perpendicular 

 to the rings, along the recognizable major axis of 

 sagittal growth after year 1. Additional sections 

 were made of sagittae from 10 randomly chosen fish: 

 one longitudinal section, and two sections at 45° 

 perpendicular to each other. The purposes of these 

 sections were to determine if there was evidence for 

 splitting of rings and to ensure that the transverse 

 section, described above, was the most legible prep- 

 aration. All whole and sectioned sagittae were ex- 

 amined by two readers, and the age was excluded 

 from analyses if the readers did not agree. Sex was 

 determined by gross examination and was verified 

 histologically in subsamples. Regressions of fork 

 length on otolith radius were performed for sexes 

 separately and combined. Back-calculated sizes at 

 age were computed for males, females, and sexes 

 combined by the Fraser-Lee method (Carlander 

 1982; Poole 1961). The SAS NLIN procedure (SAS 

 Institute 1982) was used to fit von Bertalanffy equa- 

 tions to the weighted mean back-calculated lengths 

 at age. 



RESULTS 



The astericus was not detected in any larvae, sug- 

 gesting it forms at >7 mm SL. All larval lapilli had 

 well-defined presumed daily rings that were easily 



50 



