Four New Cardinalfishes (Perciformes: Apogonidae) from the Marquesas Islands

Abstract

Four species of Apogonid fishes are described as new from the Marquesas Islands. Apogon lativittatus, similar to A. semiornatus, differs in having 13 instead of 12 pectoral rays, 4.5-5.5 scales above the lateral line, 19-23 circum-peduncular scales, a straighter dorsal profile of the head, deeper body on the average, opaque red color as an adult with the same midlateral blackish stripe posteriorly on the body and caudal fin, but the oblique dark band on head reduced, and in larger size (to 58.4 mm SL); the type specimens include one from the Line Islands (A. semiornatus remains unknown from islands of Oceania). Apogon relativus, with five dark stripes and pink fins, is similar to A. angustatus, differing in having narrower stripes, a larger and vertically elongate black spot at midbase of caudal fin in adults, and a broader interorbital space (bony width 4.05-4.8 in head, compared with 5.0-5.95 for A. angustatus). Apogon sinus, collected in very shallow water at the head of deep bays, is uniquely colored with seven narrow dark stripes on the body, but none on the lower third of body anterior to the caudal peduncle; it is most similar to the wide-ranging allopatric A. taeniophorus, from which it differs in a deeper body (2.6-2.9 in SL, compared with 2.8-3.2), broader interorbital space (4.2-4.45 in head, compared with 4.5-5.35), and in having 16-17 instead of 17-19 gill rakers. Pseudamiops phasma is described from two specimens. Like the three other species of the genus, it is elongate and compressed, with deciduous cycloid scales, no lateral line, ventral spine posteriorly on the maxilla, and largely transparent body; it differs variously from the others, but from all in having 19 compared with 14-18 pectoral rays.

The fish fauna of the Marquesas Islands in the South Pacific, the northernmost archipelago of French Polynesia, is relatively impoverished. Only 415 species of shore fishes are known from these islands (Randall and Earle in press), compared with 633 for the Society Islands (Randall 1985, revised by Myers 1999). Although there has probably been more fish collecting in the Societies, it is very evident that there are fewer fishes in the Marquesas when one compares the number of species in families of which the species are readily observed and collected. For example, the Society Islands has 27 chaetodontids, 11 pomacanthids, 33 pomacentrids, 50 labrids, and 19 scarids. The respective numbers for these families in the Marquesas are 15, 3, 21, 33, and 6.

The Marquesas are also special in having the third highest level of endemism of shore fishes in the Pacific, 11.6% (Randall and Earle in press), after Hawaìi with 23.1% and Easter Island with 22.2% (Randall 1998). The basis for the high endemism of the Marquesas appears to be their isolation and variable sea temperature.

The Marquesas lie between latitude 7° 50{0}´S and 10° 35´S and longitude 138° 25´W and 14° 50´W. They are high islands of volcanic origin that rise steeply from the sea bottom at depths greater than 4000 m. There are no barrier reefs, hence no lagoons, and relatively little live coral. The sea-surface temperature for the region from 1982 to 1998 averaged 27.5°C, with extremes of 26.5 and 30.0°C. This is a large range of open-ocean sea temperature for a locality so near the equator. The cooler temperature is from equatorial upwelling, and the higher temperature from El Niño. The warming from El Niño would result in a greater temperature change in the Marquesas than at other low-latitude islands to the west. If the sea-surface temperature were as high as 30°C in the open ocean, still higher sea temperature would be expected at times inshore, depending on other factors such as circulation and diurnal heating.

The nearest islands to the Marquesas are the atolls of the northern Tuamotu Archipelago some 500 km to the southwest. There...