Kingfishes (whitings), Menticirrhus spp.

Transcription

1 Kingfishes (whitings), Menticirrhus spp. Three species of whitings are present in Florida: southern kingfish, Menticirrhus americanus; northern kingfish, M. saxatilis; and gulf kingfish, M. littoralis. The southern kingfish, followed by gulf kingfish, are the two most common kingfish landed in Florida. Southern kingfish are demersal and occur over a wide variety of mud and sand substrates. Adults and juveniles prefer the sand bottoms of ocean beaches and the mouths of large coastal bays (Bearden 1963). In a survey of U.S. south Atlantic nearshore waters, Smith and Wenner (1985) found that 90% of the southern kingfish that they collected were age 2 or younger. The largest fish collected was 16 inches total length (TL); the oldest fish was age 6. Most southern kingfish mature at age 1, when males and females reach an average of 5.4 inches 7.9 inches TL (Smith and Wenner 1985; Armstrong and Muller 1996). Spawning occurs from April through August. Table 1. Von Bertalanffy growth parameters and length-weight relations for southern kingfish Inches TL = L (1-e -K(age-t 0 ) ) K L (inches TL) t 0 (years) Source Males, South Atlantic Bight Smith and Wenner (1985) Females, South Atlantic Bight Smith and Wenner (1985) Weight in lbs = a (inches TL) b A b Source Combined sexes, South Atlantic Bight Smith and Wenner (1985) Table 2. Von Bertalanffy growth parameters and length-weight relations for northern kingfish Inches TL = L (1-e -K(age-t 0 ) ) K L (inches TL) t 0 (years) Source Males, South Atlantic Bight Schaefer (1965) Females, South Atlantic Bight Schaefer (1965) Weight in lbs = a (inches FL) b A b Source Sex combined, South Atlantic Bight Schaefer (1965) Table 3. Length-weight relations for gulf kingfish Weight in lbs = a (inches FL) b A b Source Sex combined, South Atlantic Bight Music and Pafford (1984) Florida Fish and Wildl. Conservation Comm., FWRI (2006) WHITINGS - 1

2 Southern kingfish are reported to be voracious bottom feeders that eat a variety of organisms. Juvenile kingfish feed on copepods, bivalve siphons, mysids, amphipods, polychaetes, and cumaceans (Music and Pafford 1984). Larger fish feed on various crab species, isopods, fishes, amphipods, and polychaetes (Bearden1963; McMichael 1981). McMichael and Ross (1987) found that northern kingfish in the northern Gulf of Mexico fed on isopods, crabs, fishes, polychaetes, amphipods, mysids, and cumaceans. Similarly, gulf kingfish fed on bivalve siphons, cumaceans, mysids, copepods, amphipods, and polychaetes (McMichael and Ross 1987). A total of 2,423,045 pounds of kingfish were landed in Florida during The recreational fishery made sixty-seven percent of the total landings in Nearly 82% of the statewide total landings were made on the Atlantic coast. The commercial landings were greatest in Duval County on the Atlantic coast and in Pinellas and Manatee Counties along the gulf coast (Fig. 1). Recreational landings were distributed evenly along the Atlantic coast and south of Levy County on the gulf coast (Fig. 2). The 2005 total landings of kingfish were 64% higher than the average landings in the previous five years ( ) and were 25% higher than the historical average landings (Fig. 3). The recreational catch was primarily southern kingfish on the Atlantic coast and a mixture of southern and gulf kingfish on the gulf coast. Total landings on the Atlantic coast averaged 1.4 million pounds during , one million pounds during (Fig. 3), 1.4 million pounds in 2001, only 0.7 million in 2003, and the 2005 landings were the highest since Gulf landings occasionally showed strong peaks: one during 1986 and again during Total gulf landings have been slowly increasing since The standardized commercial catch rates are for a mixture of species but predominantly for southern kingfish, which probably comprises most of the commercial landings (Armstrong and Muller 1996). Commercial catch rates steadily increased between 1993 and 1997 on the Atlantic coast before declining after 2000, since 2003 catch rates have been increasing rapidly (Fig. 4). On the gulf coast, commercial catch rates slowly declined between 1992 and 1997, fluctuated around 10 pounds per trip from , then increased dramatically in 2005 (Fig 5). Commercial catch rates for both coasts were the highest in 2005 since 1992 (Figs. 4,5). Angler total-catch rate estimates for southern kingfish declined between 1990 and 1999 on the Atlantic coast, spiked in 2000, declined through 2004 then spiked again in 2005 (Fig. 6). Gulf coast angler total-catch rates were fairly steady from , but almost doubled in 2005 (Fig. 7). Atlantic coast recreational catch rate estimates for gulf kingfish increased during but dropped in 2000 and have since increased slowly through 2005 (Fig. 8). On the gulf coast, angler catch rates for gulf kingfish declined from , increased rapidly through 2000, dropped in 2001, and have since rebounded through 2005 (Fig. 9). Fishery-independent indices for young-of-the-year (YOY) southern kingfish have been high on the Atlantic coast from following an extremely low year in 2000, while on the gulf coast indices have varied without trend (Figs. 10, 11). Post-YOY southern kingfish abundances on the Atlantic coast were higher from following low abundances in 1999 and 2000, while gulf coast abundances varied without trend and were highest in 2000 (Figs. 12,13). No occurrences of gross external abnormalities were recorded in southern kingfish from the Atlantic coast. On the Atlantic coast, incidences of gross external abnormalities among southern kingfish were highest in 2001 and 2004, and consisted primarily of parasites (Figs. 14, 15). No formal stock assessments for these three species are available at this time. Florida Fish and Wildl. Conservation Comm., FWRI (2006) WHITINGS - 2

3 Figure 1. Geographic distribution of commercial landings of kingfishes during 2005 Figure 2. Geographic distribution of recreational landings of kingfishes during 2005 Com-Atlantic Rec-Atlantic Com-Gulf Rec-Gulf Figure 3. Total annual landings of kingfishes (whitings) on the Atlantic and gulf coasts of Florida, Florida Fish and Wildl. Conservation Comm., FWRI (2006) WHITINGS - 3

4 Figure 4. Annual standardized commercial catch rates (pounds) for kingfishes (whitings) on the Atlantic coast of Florida, Figure 5. Annual standardized commercial catch rates (pounds) for kingfishes (whitings) on the gulf coast of Florida, Florida Fish and Wildl. Conservation Comm., FWRI (2006) WHITINGS - 4

5 Figure 6. Annual standardized recreational total-catch rates (numbers) for southern kingfish on the Atlantic coast of Florida, Figure 7. Annual standardized recreational total-catch rates (numbers) for southern kingfish on the gulf coast of Florida, Florida Fish and Wildl. Conservation Comm., FWRI (2006) WHITINGS - 5

6 Figure 8. Annual standardized recreational total-catch rates (numbers) for gulf kingfish on the Atlantic coast of Florida, Figure 9. Annual standardized recreational total-catch rates (numbers) for gulf kingfish on the gulf coast of Florida, Florida Fish and Wildl. Conservation Comm., FWRI (2006) WHITINGS - 6

7 Figure 10. Proportion of fishery-independent-monitoring sets on the Atlantic coast that captured young-of-the-year southern kingfish, Figure 11. Proportion of fishery-independent-monitoring sets on the gulf coast that captured young-of-the-year southern kingfish, Florida Fish and Wildl. Conservation Comm., FWRI (2006) WHITINGS - 7

8 Figure 12. Proportion of fishery-independent-monitoring sets on the Atlantic coast that captured post-young-of-the-year southern kingfish, Figure 13. Proportion of fishery-independent-monitoring sets on the gulf coast that captured post-young-of-the-year southern kingfish, Florida Fish and Wildl. Conservation Comm., FWRI (2006) WHITINGS - 8

9 Figure 14. Proportion of southern kingfish 75 mm collected in fishery-independentmonitoring sets on the gulf coast that had gross external abnormalities, Figure 15. Proportions of different gross external abnormalities in southern kingfish 75 mm collected in fishery-independent-monitoring sets on the gulf coast, Florida Fish and Wildl. Conservation Comm., FWRI (2006) WHITINGS - 9