An evaluation of Northern Florida Bay as a nursery area for red drum, Sciaenops ocellatus, and other juvenile and small resident fishes.

Red drum is one ofthe most popular species sought by anglers in Florida Bay, yet juveniles are rarely encountered. We evaluated Florida Bay as a nursery area for red drum by sampling for recently-settled late larvae in basin areas within the bay with an epi-benthic sled at six stations in November 2000, and at seven stations during December 2000 through February 2001. In November 2000 we surveyed potential sampling sites in quiet backwaters adjacent to mangroves for juvenile red drum. A total of 202 sites were sampled mainly in northern Florida Bay and adjacent waters with a cast net. We collected only one recently-settled red drum larvae and no juveniles. Obviously the sites that we sampled in Florida Bay and adjacent waters are not nursery habitat for this valuable species. Sled collections were dominated by bay anchovy, Anchoa mitchilli, but densities were biased by one collection. Five small resident species were among the dominant species: rainwater killifish, Lucania parva; dusky pipefish, Syngnathus floridae; dwarf seahorse, Hippocampus zosterae; and clown goby, Microgobius gulosus. Three species that spawn outside Florida Bay in the GulfofMexico were common: pinfish, Lagodon rhomboides; pigfish, Orthopristis chrysoptera; and silver perch, Bairdiella chrysoura. Twenty-seven species were collected with the cast net. Hardhead silversides (Atherinomorus stipes), bay anchovy, tidewater mojarra (Eucinostomus harengulus), silver jenny (Eucinostomus gula), and goldspotted killifish (Floridichthys carpio) were the most common in cast net collections. Although only one red drum was collected, we were able to: (1) identify mesohaline waters from our cast net sites to test our preliminary assessment that mesohaline habitat might be limited in Florida Bay, (2) document the distribution and abundance of fishes collected by cast net that should enhance our understanding of ichthyofauna in the Northern Subdivision ofFlorida Bay and adjacent waters, and (3) from epibenthic sled collections, describe the habitats, abundance and distribution of recently settled larvae/small juveniles/small resident fishes during late fall and winter. This information should be useful to managers and future research. (PDF contains 34 pages)

Comparative growth and survival of fry of Clarias gariepinus (B), Clarias anguillaris (L), Heterobranchus bidorsalis (G), Heteroclarias, Clariabranchus and Clarias hybrids under outdoor nursery management system

Hybrids of Clariid catfishes; C. gariepinus (Netherlands), C. anguillaris, H. bidorsalis and their parental species were monitored for 8 weeks in 2 x 2 x 1m outdoor concrete tanks. The fry were fed NIFFR diet (40% crude protein) twice daily, 7 days of the week. Growth and survival records were taken weekly. The male HEB X female CLG hybrid showed an overall highest performance in growth rate while the lowest was recorded in male CLA X female CLG hybrid. The male HEB X female CLG hybrid grew at a faster rate than its reciprocal hybrid. In view or their growth rate, it is possible that the growth and survival rates or H. bidorsalis especially at the fry to fingerling stage could be improved through hybridization. The hybrid have potential as commercial food fish

All their eggs in one basket: a rocky reef nursery for the longnose skate (Raja rhina Jordan & Gilbert, 1880) in the southern California Bight

Skates (family Rajidae) are oviparous and lay tough, thick-walled eggs. At least some skate species lay their eggs in spatially restricted nursery grounds where embryos develop and hatch (Hitz, 1964; Hoff, 2007). After hatching, neonates may quickly leave the nursery grounds (Hoff, 2007). Egg densities in these small areas may be quite high. As an example, in the eastern Bering Sea, a site <2 km2 harbored eggs of Alaska skate (Bathyraja parmifera) exceeding 500,000/km2. All skate nursery grounds have been identified over soft sea floors (Lucifora and García, 2004; Hoff, 2007).

A nursery site of the Alaska skate (Bathyraja parmifera) in the eastern Bering Sea

A nursery site for the Alaska skate (Bathyraja parmifera) was sampled seasonally from June 2004 to July 2005. At the small nursery site (~2 km2), located in a highly productive area near the shelf-slope interface at the head of Bering Canyon in the eastern Bering Sea, reproductive males and females dominated the catch and neonate and juvenile skates were rare. Seasonal samples showed summertime (June and July) as the peak reproductive time in the nursery although some reproduction occurred throughout the year. Timeseries analysis of embryo length frequencies revealed that three cohorts were developing simultaneously and the period of embryonic development was estimated at 3.5 years and average embryo growth rate at 0.2 mm/day. Estimated egg case deposition occurred mainly during summertime and hatching occurred during winter months. Protracted hatching times may be common for oviparous elasmobranch species and may be directly correlated with ambient temperatures as evident from a meta-data analysis. Evidence indicates that the Alaska skate uses the eastern Bering Sea outer continental shelf region for reproduction and the middle and inner shelf regions as habitat for immature and subadults. Skate nurseries may be vulnerable to disturbances because they are located in highly productive areas and because embryos develop slowly.

Hatching date, nursery grounds, and early growth of juvenile walleye pollock (Theragra chalcogramma) off northern Japan*

Walleye pollock (Theragra chalcogramma) is widely distributed in the North Pacific Ocean and plays an important role in coastal subarctic ecosystems. The Japanese Pacific population of this species is one of the most important demersal fishes for commercial fisheries in northern Japan. The population is distributed along the Pacific coast of Hokkaido and the Tohoku area (Fig. 1), which is the southern limit of distribution of the species in the western North Pacific. In Funka Bay, the main spawning ground for this population, pollock spawn from December to March (Kendall and Nakatani, 1992). Planktonic eggs and larvae are transported into the bay, where juveniles usually remain until late July when they reach 60−85 mm in total length (Hayashi et al., 1968; Nakatani and Maeda, 1987). These juvenile pollock then migrate from Funka Bay eastward to the Doto area off southeastern Hokkaido (Honda et al., 2004). Many studies on eggs, larvae, and juveniles of the species have been conducted in or near Funka Bay, but little information is available on the ecology of the early life stages in the Tohoku area. Hashimoto and Ishito (1991) suggested that eggs are transported from Funka Bay southward to the Tohoku area by the coastal branch of the Oyashio Current, but there has been no study to verify this hypothesis.

Geographic variation among age-0 walleye pollock (Theragra chalcogramma): evidence of mesoscale variation in nursery quality?

Nurseries play an important part in the production of marine f ishes. Determining the relative importance of different nurseries in maintaining the parental population, however, can be difficult. In the western Gulf of Alaska, the Kodiak Island vicinity may be particularly well suited as a pollock nursery because of a prey-rich nearshore environment. Our objectives were 1) to examine age-0 pollock body condition, growth, and diet for evidence of a nearshore-shelf effect, and 2) to determine if variation in the potential prey field of zooplankton was associated with this effect. This was a pilot study that occurred in three bays and over the adjacent shelf off east Kodiak Island during 5−18 September 1993. Sampling occurred only during night at locations where echo sign indicated the presence of age-0 pollock. Echo sign was targeted to increase the chance of collecting fish given the limited vessel time. Fish condition was indicated by length-specific body weight. Growth rate indices were estimated for three different periods by using fish lengthage data and daily otolith increment widths: 1) from hatching date to capture, 2) 1−5 d before capture, and 3) 6−10 d before capture. Fish diet was determined from gut content analysis. Considerable variation among areas was evident in zooplankton composition, and fish condition, growth, and diet. However, relatively high prey densities, as well as fish condition and growth rates indicated that Chiniak Bay was particularly well suited as a pollock nursery. Hatching-date distributions indicated that most of the age-0 walleye pollock from bays were spawned earlier than were those from the shelf. The benefit of being reared in nearshore areas is therefore realized more by individuals that were spawned early than by individuals spawned relatively late.