NYMAN and CONOVER: YOUNG-OF-THE-YEAR BLUEFISH 



Frequency of Ring Deposition 



The frequency of growth ring deposition was 

 determined by marking the otoliths of fish with 

 tetracycline and then subsampling the marked 

 fish at various periods of time thereafter (Cam- 

 pana and Neilson 1982). Sixty YOY bluefish (7- 

 10 cm FL) were captured by seine in Flax Pond, 

 Old Field, NY (Fig. 1) and were transported to the 

 Flax Pond Laboratory of SUNY Stony Brook. The 

 fish were anesthetized in a solution of MS-222 (30 

 mg/L) and given an intraperitoneal injection of 

 tetracycline (100 mg/kg offish). After injection, 

 all fish were placed in a 1.3 x 1.3 m cylindrical 

 floating cage constructed out of 5 mm plastic 

 mesh and anchored in Flax Pond. The fish were 

 fed chopped Menidia menidia twice a day, and 

 dead bluefish were removed daily. Samples of 5- 

 10 healthy fish were periodically taken from the 

 cage using a dip net and frozen until the otoliths 

 could be excised. The experiment was terminated 

 61 days after the injections. 



After preparation as described above, the 

 tetracycline-treated otoliths were viewed on a 

 Zeiss compound microscope using reflected ultra- 

 violet (UV) light at 160-400 X. Tetracycline fluo- 

 resces upon exposure to UV light, thus enabling 

 the location of the marked ring to be determined. 

 The UV light was then turned off, and the num- 

 ber of rings from the mark to the edge of the 

 otolith was counted under transmitted white 

 light. Each otolith preparation was coded so that 

 the reader did not know the true age. Three repli- 

 cate counts were conducted on each otolith. 



RESULTS 



Temporal Abundance and Length 

 Frequency 



Great South Bay 



The appearance of YOY bluefish in the shore 

 zone was abrupt in both years of the study. In 

 1985, no YOY bluefish were caught in weekly 

 samples until 28 May when a catch per unit effort 

 (CPUE = no. fish per seine haul) of 14.0 was 

 recorded (Fig. 2a). Corresponding water tempera- 

 ture was about 20°C. CPUE declined steadily 

 thereafter through October with two exceptions: 

 the large collections on 10 and 28 July were each 

 due to an unusually large number offish in single 

 seine hauls in the Carmans River. In 1986, YOY 

 bluefish were first caught on 10 June when the 



water temperature was 24°C. The maximum 

 CPUE (45.3) was obtained on 16 June and was 

 followed by a decrease in CPUE in subsequent 

 collections (Fig. 2b). 



Length-frequency distributions in 1985 showed 

 the progression of a single mode through mid- 

 August (Fig. 3a). Newly recruited fish in late May 

 were 3-6 cm FL. Subsequent samples showed an 

 increase in the mean and range of fish lengths, 

 probably due to somatic growi;h of the initial re- 

 cruits. There was no evidence of new 3-6 cm re- 

 cruits entering the shore zone later in the year 

 (Fig. 3a). Although seining continued until 

 November, very few YOY bluefish were caught 

 after August. An additional sample {n = 8) taken 

 on 16 September by angling from a pier on Great 

 South Bay had a mean fork length of 17.8 cm and 

 a range of 14.6-19.5 cm. Length-frequency data 

 from 1986 (Fig. 3b) show a very similar pattern to 

 that in 1985: a single length mode appears in 

 June and these fish increase in size through the 

 summer. Few YOY bluefish were caught in Au- 

 gust, September, or October. 



Size at recruitment to the shore zone was simi- 

 lar in both years of our study: mean length of the 

 1985 and 1986 year classes at first appearance in 

 the shore zone was 4.6 and 4.5 cm respectively 

 (Fig. 4). However, because the 1986 year class 

 first appeared in the shore zone two weeks later 

 than did the 1985 year class (Fig. 2), the mean 

 lengths of 1986 year class were less than those of 

 1985 on comparable dates in June and early July. 

 By mid-July, however, this difference in mean 

 length of the two year classes was no longer ap- 

 parent. Both year classes reached a size of about 

 13-14 cm by late August when they rarely ap- 

 peared in our seine collections. 



Setauket Harbor 



In 1986, the YOY bluefish did not appear on the 

 north shore of Long Island at Setauket Harbor 

 until 3-6 weeks after they first appeared in Great 

 South Bay. Collections at Setauket Harbor were 

 small at first with only one individual being 

 caught on 1 July and three on 8 July. It was not 

 until 22 July that catches similar in number to 

 those in Great South Bay were being obtained. 

 These fish had similar mean lengths (10.2 cm, 

 n = 87, on 22 July; 11.9 cm, n = 22, on 5 August; 

 13.9 cm, n = 17, on 20 August) to those on com- 

 parable dates from Great South Bay (of. Fig. 4). 

 Length-frequency distributions by date were uni- 

 modal. 



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