Deep-Water Dragonets (Teleostei: Callionymidae: Foetorepus) of the Mid Atlantic Bight: A Little-Known Genus from the Edge of the Continental Shelf
The ranges of two rare species of deep-water dragonets—the Spotfin Dragonet Foetorepus agassizii (Goode and Bean, 1888) and the Palefin Dragonet Foetorepus goodenbeani Nakabo and Hartel, 1999—overlap on the outer continental shelf of North America in the Mid Atlantic Bight. We studied more than 450 specimens collected between 2009–2015 by the Northeast Fisheries Science Center to photographically document these species, better characterize their geographic and depth distributions, and describe aspects of their reproductive biology. The two species occurred in a small subset of locations within the sampled area (81 of 6,225 stations). Although F. agassizii and F. goodenbeani occur within a similar geographic region, F. agassizii occurs at greater depths, on average 33 m deeper, than F. goodenbeani. Collection locations and depths in spring and fall were similar, suggesting that F. agassizii and F. goodenbeani do not migrate seasonally, perhaps because they occur in habitats with stable year-round temperatures. Macroscopic and histological analyses of reproductive condition indicated both species are spawning capable in spring (March) and fall (September and October). Males collected in these months had mature spermatozoa in testicular tubules, and females had oocytes in many stages, indicative of asynchronous oocyte development and batch spawning. Ovarian weight, however, was greater in specimens collected in fall months, indicating a peak in spawning.
Photographs of two species of Foetorepus. (A) Foetorepus agassizii, 105 mm SL, male, collected 17 September 2013, KEB 0577, CUMV 98709. Note the prominent black, ocellated spot in the fin web between the third and fourth fin rays of the first dorsal fin that is not present in F. goodenbeani. (B) Foetorepus goodenbeani, 162 mm SL, male, collected 29 September 2013, KEB 0303, VIMS 34870. Note that the first dorsal-fin ray is elongated in comparison to that of F. agassizii.
Photographs of live Foetorepus goodenbeani recorded at depth just south of the Hudson Canyon by ROV SEABOSS operated by P. Valentine and D. Blackwood, USGS, and provided for use by Vince Guida, NOAA NEFSC. The bottom type in all four photographs is fine mud. Where visible, the tip of the first dorsal-fin ray is indicated with black arrows; its long length distinguishes F. goodenbeani from F. agassizii. (A) An individual using its pectoral fins to hover above the substrate at 130 m deep, 1645 hrs, 25 October 2002. (B) A second individual at the same site and time as the specimen shown in A; a ceriantharian is about 10 cm to the right of the fish. (C) An individual lightly covered with mud at 114 m deep, 1340 hrs, 31 October 2002. (D) An individual resting on the substrate at 156 m deep, 1740 hrs, 27 August 2004.
Charts of the western North Atlantic showing 6,225 stations sampled (black dots) from March 2009 to April 2015 and occurrences of two species of Foetorepus categorized by the number of specimens captured. Nearly all stations that yielded Foetorepus are on the outer continental shelf between Oceanographer and Norfolk canyons. Most specimens were collected near the shelf break deeper than 111 m. (A) Occurrence of F. agassizii. Stations with the highest numbers of captures are near the Hudson Canyon, with three stations yielding more than 15 specimens per tow. One station near Baltimore Canyon and another near Alvin Canyon also yielded more than 15 specimens. A single specimen was captured south of Cape Hatteras. (B) Occurrence of F. goodenbeani. Stations with the highest numbers of captures are near the Hudson Canyon. Most specimens were taken in the region from Alvin Canyon to just south of Hudson Canyon. Several stations between 56 m and 111 m produced single specimens.
Plots of station depth, latitude, and numbers of individuals of the two species of Foetorepus captured at all stations north of Cape Hatteras. Foetorepus agassizii occurs at greater depths, on average 33 m deeper, than F. goodenbeani.
Seasonal change in interpolated bottom temperatures in the Mid Atlantic Bight and Georges Bank. Shallow areas near the coast have greater temperature fluctuations between spring and fall, but Foetorepus live on the continental shelf in a region of relatively stable bottom temperatures. Blue circles indicate spring collections and red circles indicate fall collection of Foetorepus, and these distributions are similar during the two seasons.
Gonadal histology of Foetorepus agassizii (A–D) and F. goodenbeani (E–G); sections of tissues from spring collected specimens are on the left (A, C, E) and fall collected are on the right (B, D, F, G). (A) Section through ovary of specimen collected 29 March 2015, 126 mm SL, KEB 615, VIMS 34884; many oocyte stages are evident, indicative of asynchronous oocyte development and batch spawning. (B) Section through ovary of spawning active female collected 8 September 2013, 158 mm SL, KEB 589, CUMV:Fish 98733; oocytes and POFs indicate spawning active subphase. (C) Section through testis of spawning capable male collected 29 March 2015, 135 mm SL, KEB 614, VIMS 34884; mature spermatozoa are abundant in spermatocysts. (D) Section through testis through spawning capable male collected 17 September 2013, 103 mm SL, KEB 578, CUMV:Fish 98709; mature spermatozoa are present in spermatocysts. (E) Section through ovary of spawning active female collected 28 March 2015, 175 mm SL, KEB 608, VIMS 34873; late vitellogenic oocytes present, and fresh POF indicated in inset. (F) Section through ovary of spawning active female collected 18 September 2013, 159 mm SL, KEB 562, CUMV:Fish 98707; oocytes in final maturation (GVBD, HO) and older POF present. (G) Section through testis of spawning capable male collected 17 September 2013, 183 mm SL, KEB 552, VIMS 34862; mature spermatozoa present in spermatocysts. Abbreviations: CA, cortical alveoli stage oocyte; GVBD, germinal vesicle breakdown stage oocyte; GVM, germinal vesicle migration stage oocyte; HO, hydrated oocyte within the follicle; OV, ovulated egg; PG, primary growth stage oocyte; POF, post ovulatory follicle; SC, spermatocyte; SG, spermatogonia; SZ, spermatozoa; V1, early vitellogenic stage oocyte; V2 late vitellogenic stage oocyte. All sections stained with periodic acid Schiff-Mallory trichrome.
Contributor Notes
Associate Editor: D. Buth.