DITTY: ICHTHYOPLANKTON IN NERITIC WATERS 



and were collected throughout the year, but were 

 most abundant in June and least abundant in 

 November (Table 1). Anchovies accounted for 65% 

 of all larvae taken during the spring and 69% dur- 

 ing the summer, but declined to about 6% of all lar- 

 vae collected during the fall and winter, respectively; 

 anchovies were the second most abundant taxon col- 

 lected during the winter and were fourth during the 

 fall. Most anchovy larvae were collected near the 

 surface and middepths; only 11% were collected 

 near the bottom. A few flat anchovy, Anchoviella 

 perfasciata, postlarvae were collected in February 

 only. 



Atlantic croaker accounted for 66% of all sciaenid 

 larvae and were most abundant in November (Table 

 1). This species accounted for 58% of all larvae taken 

 during the fall and for 14% of larvae overall. Most 

 Atlantic croaker (65%) were collected near middepth 

 with only 1% collected near the surface. Two types 

 of sand seatrout, Cynoscion arenarins, were recog- 

 nized with Type A collected from April to September 

 and Type B from April to October. Of all sand 

 seatrout larvae taken, 60% were Type A and 40% 

 Type B, with Type A the second and Type B the 

 third most abundant of all sciaenid larvae. Density 

 of Type A exceeded that of Type B until September 



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2 

 uj 

 Q 



< 



> 



M A 



MONTH 



Figure 3.— Density of ichthyoplankton (no./lOO m 3 ) by month, 

 from neritic Gulf of Mexico waters off Louisiana, November 1981- 

 October 1982. 



and October when Type B were more abundant 

 (Table 1). Most Type A (66%) and Type B (56%) lar- 

 vae were collected near the bottom with <5% of 

 Type A and of Type B larvae, respectively, collected 

 near the surface. Larvae of red drum, Sciaenops 

 ocellatus, were taken during the fall only and were 

 most abundant in September, whereas Menticirrhus 

 spp. were collected in all months except December 

 and January and were most abundant in October 

 (Table 1). Larval densities of other less abundant 

 sciaenids that included black drum, Pogonias cromis; 

 banded drum, Larimus fasciatus; spot, Leiostomus 

 xanthurus; silver perch, Bairdiella chrysoura; and 

 silver seatrout, Cynoscion nothus, never exceeded 

 1/100 m 3 . Densities of star drum, Stellifer lance- 

 olatus, and spotted seatrout, C. nebulosus, were 

 <2/100 m 3 for any month. 



Larvae of both the scaled sardine, Harengula 

 jaguana, and Atlantic thread herring were collected 

 from April to October, whereas gulf menhaden were 

 collected from October to February and round her- 

 ring, Etrumeus teres, only in January and February. 

 No larvae of Spanish sardine, Sardinella sp., were 

 identified. Densities of Atlantic thread herring were 

 greatest in June, scaled sardine in July, and gulf 

 menhaden in January. Densities of Atlantic thread 

 herring accounted for about 58% of all clupeid larvae 

 and for 9% of larvae overall; gulf menhaden 

 accounted for 34% of all clupeids and for 5% of lar- 

 vae overall. Scaled sardine accounted for 8% of all 

 clupeid larvae. Atlantic thread herring was the sec- 

 ond most abundant taxon collected in each season 

 except winter, and accounted for 88% of all clupeid 

 larvae collected between April and October; gulf 

 menhaden accounted for 73% of all winter larvae. 

 Over 99% of Atlantic thread herring and 80% of 

 scaled sardine were collected when surface water 

 temperatures were above 25°C; 90% of gulf men- 

 haden were taken at water temperatures below 

 20°C. Most scaled sardine (79%) larvae were taken 

 near the surface and only 2% near the bottom. Men- 

 haden larvae were abundant at all depths with 37% 

 collected near the surface and 24% near the bottom. 

 Atlantic thread herring were most abundant near 

 middepth (62%) and least abundant near the surface 

 (6%). 



Larvae of Atlantic bumper were collected from 

 June to October but were most abundant in July. 

 This species accounted for about 5% of all larvae 

 and was the third most abundant taxon collected 

 during both the summer and fall months. Atlantic 

 bumper accounted for about 94% of all carangid lar- 

 vae with most bumper (94%) collected when surface 

 water temperatures averaged 30°C. Atlantic 



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