Spatial and seasonal patterns in species composition of fish larvae in the Canary Islands

SPATIAL AND SEASONAL PATTERNS IN SPECIES COMPOSITION AND OCCURRENCE OF FISH LARVAE IN THE AREA OF THE CANARY ISLANDS, EASTERN CENTRAL ATLANTIC

-- Morphology: The larvae hatch with a size of 3 mm and the tiny premaxillary teeth form already at 4 mm and persist throughout the larval development till the juvenile stage. The head is small with a length less than 1/3 of the SL and the snout is rounded, so the head profile curves gently. The jaws are equally in length and tiny premaxillary teeth develop. The number of myomeres is 31 and all vertebrae are ossified at a size of 7.6 mm. There are no larval specializations, so no spination forms out. Unique for this genus is, that the first dorsal fin develops after the second has formed and is completed with a size of 13 mm. In the studied specimens all fins as well as the finlets had already formed out (Figure 70).

-- Pigmentation: Strong pigmentation develops ventrally on the trunk especially at the level of the midbody and posterior to the anus along the tail. Further pigmentation is located at the fore- and hindbrain, at the tip of the lower jaw.The same pigmentation pattern is found in S. scombrus LINNAEUS, 1758, but it develops later in larval development and a pigmentation at the cleithral symphysis is present, which is absent in S. colias (Figure 70).

-- Reference: COLLETTE (1986); COLLETTE et al. (1984); FAHAY (1983);

-- Reference material: 50 specimens; 03/02: S1 (P74172); S4 (P74173-174); S5 (P74177); S6 (P74179); S11 (P74180-218); S14 (P74178); S17 (P74175-176); S19 (P74169-71);

-- Distribution: Larvae only were caught in late winter southeast of Fuerteventura, whereas most larvae occurred at epipelagic stations in a depth range of 22 – 140 m in day as well as in night time. Further each one specimen was caught at a neritic station in depths of 15 – 60 during the night and some larvae were caught also at mesopelagic stations in a depth range of 311 – 378 m and 617 – 915 m each during the day.

STROMATEIODEI > Nomeidae The body is deep during whole larval period and even increases with development to more than 1/3 of SL in postflexion larvae.The length of the gut is less than half of NL initially and increases to more than 50 % of SL in late larvae. Also the head length increases to about 1/3 of the SL. Flexion takes place at a size range from 4.5 – 5 mm SL. Along the preoperculum very small, almost not visible spines start to develop at 5.2 mm and disappear again at a size of approximately 11 mm of SL. Head pigmentation is present dorsally on the head, at the tips of the jaws, and ventrally from the snout to the cleithrum. Further melanophores develop at the dorsal and lateral surface of the gut and ventrally along the midline of the caudal peduncle in preflexion stage, but latter vanish during postflexion stage. All other melanophores increase in number and size in larvae exceeding 7 mm SL and stellate melanophores starts to cover the entire body.

-- Reference: OLIVAR and FURTAÑO (1991);

Inf. Téc. Inst. Canario Cienc. Mar. n°13

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