BERRIEN: EGGS AND EARLY LARVAE OF ATLANTIC MACKEREL 



vae have more melanophores on the yolk surface 

 than S. scombrus; and S. scombrus larvae, 

 during and at the end of yolk absorption have 

 several dorsal trunk melanophores, whereas 

 few S. japonicus at this stage have any such 

 pigmentation. In those S. japonicus which have 

 dorsal melanophores on the trunk, it is apparently 

 limited to a single patch near the 23rd myomere 

 (Fry 1936; Uchida et al. 1958; Kramer 1960). 

 Separation of the two species of Scomber early- 

 stage eggs, before blastopore closure, may be 

 impossible on the basis of morphological char- 

 acters. Other factors, such as spawning time and 

 area, and the proximity of older, identifiable 

 stages, may be necessary for subjective identi- 

 fications. 



PROCEDURES 



Running ripe Atlantic mackerel were caught 

 by hook and line off Fire Island, Long Island, 

 N.Y., during the morning of 2 June 1967. Several 

 hundred eggs were stripped from one female and 

 fertilized in a liter jar containing a small amount 

 of sea water. The water was renewed about 20 min 

 after introduction of the eggs and sperm, and the 

 jar placed in a water bath to minimize tempera- 

 ture changes. The water temperature generally 

 increased during egg incubation and larval life 

 and ranged from 12.1° to 14.4°C for eggs and from 

 14.1° to 15.2°C for larvae (Table 1). Larvae were 

 not fed and none survived longer than 8 days past 

 hatching. Samples of the developing eggs and 

 larvae were removed at intervals and preserved 

 in dilute Formalin. ^ 



While the following descriptions of eggs were 

 based mainly on cultured eggs, planktonic eggs 

 were utilized in obtaining dimensions (Table 2) 

 and in confirming pigmentation, which tended 

 to be faded and obscure in the cultured speci- 

 mens. Owing to the internally damaged condition 

 of early-stage eggs from plankton samples only 

 middle- and late-stage eggs from that source 

 were used for the above purposes. In the early- 

 stage eggs the yolk and oil globule membranes 

 ruptured and allowed the yolk and fractured oil 

 globule to mix with perivitelline fluid. Planktonic 

 eggs were taken by Gulf V high-speed samplers, 

 with 0.4-m mouth and 0.52-mm mesh openings. 



Table 1. — Dimensions of Atlantic mackerel larvae, cultured 



^Reference to trade names does not imply endorsement by 

 the National Marine Fisheries Service, NOAA. 



The samples were taken in step-oblique tows at 

 depths between and 33 m, at a speed of 5.0 knots. 



DESCRIPTION OF THE EGG 

 Dimensions 



Formalin-preserved Atlantic mackerel eggs are 

 spherical and have clear and unsculptured shells 

 (Figure 1). The mean diameter of eggs from plank- 

 ton samples is 1.13 mm (range 1.01 to 1.28 mm) 

 and of those that were cultured is 1.20 mm (range 

 1.13 to 1.25 mm, Table 2). The cultured eggs 

 were stripped from a single female, while those 

 from plankton samples undoubtedly were 

 spawned by many. This may account for the 

 smaller range in egg diameter from the cultured 

 series and the difference in mean diameters from 

 the two sources. Differential shrinkage of egg 

 diameter, due to varying time in preservation, 

 between cultured and planktonic eggs is assumed 

 negligible, as all eggs were measured more than 

 a year after preservation. 



The egg contains a single oil globule which is 

 generally spherical and yellow or pale amber. Its 

 diameter ranges from 0.22 to 0.38 mm, with a 

 mean for all samples of 0.29 mm (Table 2). 

 In many of our preserved samples, from both the 

 cultured and planktonic eggs, the oil globules 

 were fractured or distorted. The dimensions pre- 

 sented here lie wdthin the range of those given 

 by previous authors who have studied Atlantic 

 mackerel. Published observations on eggs of this 

 species from western North Atlantic waters report 

 a ran^e in egg diameter of 0.88 to 1.38 mm, with 

 mean or modal values of 1.15 to 1.30 mm, and 

 an oil globule diameter of 0.24 to 0.32 mm (Moore 

 1899; Dannevig 1919; Bigelow and Welsh 1925; 

 Sparks 1929; Sette 1943; Merriman and Sclar 

 1952; Wheatland 1956; Marak and Colton 1961). 



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