| Family | Scientific Name | Author | Year | Common Name |
| Sternoptychidae | Argyropelecus olfersii | (Cuvier) | 1829 | Silver Hatchetfish |
All Argyropelecus Species: Body laterally compressed, deep, greatest body depth 0.8 to 2.0 in Standard Length. Exposed bony dorsal blade ahead of dorsal fin; iliac or postabdominal spines present. Eyes tubular, directed dorsally. PV photophores 12.
Argyropelecus olfersii
Unique Characteristics: Supra-abdominal, preanal, and subcaudal photophores in a nearly continuous straight line; subcaudal photophore group in a single glandular cluster, no appreciable gap between each photophore. 2 separate hypural elements in lower lobe. Two separate postabdominal spines; anal subcaudal gap less than 2.0 times anal-preanal gap. Dorsal rays 9. Both postabdominal spines of about equal length and size; anterior margin of posteriormost abdominal keel scale almost vertical. SL greater than 3.5 times body depth. Pair of enlarged canines may or may not be present in lower jaw. Subcaudal spines may or may not be present. Pair of enlarged canine teeth in lower jaw. Sharply pointed anteriormost postabdominal spine curved markedly and evenly forward; upper preopercular spine short, not extending much beyond posterior border of preopercle. Outermost tips of dorsal and ventralmost caudal rays streaked with dark pigment (fish greater than 35 mm) (Baird 1971).
Similar Species:
Argyropelecus aculeatus, Lovely Hatchetfish
Lovely Hatchetfish, Argyropelecus aculeatus. Supra-abdominal, preanal, and subcaudal photophores in a nearly continuous straight line; subcaudal photophore group in a single glandular cluster, no appreciable gap between each photophore. 2 separate hypural elements in lower lobe. Two separate post abdominal spines; anal subcaudal gap less than 2.0 times anal-preanal gap. Dorsal rays 9. Posterior post abdominal spine directed posterioventrally and markedly larger than the anterior; anterior margin of posteriormost abdominal keel scale slants markedly forward. Standard Length less than 3.4 times body depth. Pair of enlarged canine teeth present in lower jaw. Subcaudal spines present.
Argyropelecus affinis, Slender Hatchetfish
Slender Hatchetfish, Argyropelecus affinis. Supra-abdominal, preanal, and subcaudal photophores in a nearly continuous straight line; subcaudal photophores separate, an appreciable gap between each photophore. 3 separate hypural elements in lower lobe. Dorsal blade low, its heigh less than one-third its length; body margin not markedly raised posterior to dorsal blade. Ventral keel scales do not extend far below abdominal photophores. No laterally directed sphenotic spine near dorsal, posterior edge of orbit (Baird 1971).
Argyropelecus gigas, Greater Hatchetfish
Greater Hatchetfish, Argyropelecus gigas. Supra-abdominal, preanal, and subcaudal photophores not in a continuous straight line; subcaudal photophores separate, an appreciable gap between each photophore. 3 separate hypural elements in lower lobe. Dorsal blade high, its height grater than one-third its length; body margin markedly raised posterior to dorsal blade. Ventral keel scales extend well below abdominal photophores forming flaplike process; prominent laterally directed sphenotic spine near dorsal posterior edge of orbit (Baird 1971).
Argyropelecus hemigymnus, Spurred Hatchetfish
Spurred Hatchetfish, Argyropelecus hemigymnus. Supra-abdominal, preanal, and subcaudal photophores in a nearly continuous straight line; subcaudal photophore group in a single glandular cluster, no appreciable gap between each photophore. 2 separate hypural elements in lower lobe. A single posteriorly directed, serrate postabdominal spines; gap between anal and subcaudal photophore groups greater than 2.2 times gap between preanal and anal groups. Dorsal rays 8 (Baird 1971).
Argyropelecus sladeni, Lowcrest Hatchetfish
Lowcrest Hatchetfish, Argyropelecus sladeni. Supra-abdominal, preanal, and subcaudal photophores in a nearly continuous straight line; subcaudal photophore group in a single glandular cluster, no appreciable gap between each photophore. 2 separate hypural elements in lower lobe. Two separate postabdominal spines; anal subcaudal gap less than 2.0 times anal-preanal gap. Dorsal rays 9. Both postabdominal spines of about equal length and size; anterior margin of posteriormost abdominal keel scale almost vertical. SL greater than 3.5 times body depth. Pair of enlarged canines may or may not be present in lower jaw. Subcaudal spines may or may not be present. No pair of enlarged canines in lower jaw. Anteriormost postabdominal spine squared or blunt (except very small individuals), not curving evenly forward. Upper preopercular spine extends well beyond posterior border of preopercle. No pigment on outermost caudal rays (Baird 1971).
References:
Baird, R.C. 1971. The systematics, distribution and zoogeography of the marine hatchetfishes (family Sternoptychidae). Bull. Mus. Comp. Zool., Harvard Univ., 142:1-128.
Weitzman, S.H. 1986. Family No. 75: Sternoptychidae. In Smith’s sea fishes, edited by M.M. Smith and P.C. Heemstra. Johannesburg, Macmillan South Africa, pp. 253-259.