The effects of transient acid spikes on development of Lepomis sunfish were studied by combining field work with laboratory studies. Lepomis sunfish eggs were collected from rocks on nests in two freshwater ponds and ...The effects of transient acid spikes on development of Lepomis sunfish were studied by combining field work with laboratory studies. Lepomis sunfish eggs were collected from rocks on nests in two freshwater ponds and tested for their resistance to laboratory induced transient acid spikes. Fertilized eggs on rocks within the same nest were used for each pH transient experiment. Egg masses on one rock from the nest were used as a control while egg masses on another rock were exposed to transient acid spikes. Various stages of development showed different responses to the acidic effects. The major stages studied were fertilized egg, hatched with attached yolk sac, and free swimming with gills. The acid sensitivity followed development stages with the most acid sensitive stage being free swimming with gills. This fieldwork-laboratory data chain supports earlier field studies, providing the final link in an evidentiary chain showing the effects of transient acid spikes on Lepomis hatching profiles in freshwater ponds.展开更多
Hatcheries are frequently called upon to produce catchable-sized fish for stocking community fishing ponds.Desirable attributes of fish selected for stocking into community ponds are that they are easy to produce in a...Hatcheries are frequently called upon to produce catchable-sized fish for stocking community fishing ponds.Desirable attributes of fish selected for stocking into community ponds are that they are easy to produce in a hatchery system to sizes anglers are interested in catching and they provide anglers with high catch rates once stocked.Hybrid sunfish[male Bluegill(Lepomis macrochirus)×female Green Sunfish(L.cyanellus)]have attributes that potentially make them attractive for use in community fishing ponds.We assessed initial angler catch rates of 100 stocked hybrid sunfish in a 0.12-ha hatchery pond and after being subjected to angling(four,1-hr catch-and-release fishing events with five anglers).We also investigated whether catch rates would change following a supplemental stocking of an additional 100 hybrid sunfish(four,1-hr catch-and-release fishing events with five anglers).The anal fin of each fish in the second stocking was hole punched to differentiate them from those of the first stocking and fish caught by anglers were hole punched in the caudal fin each time they were caught before being released back into the pond.Angler catch rates were highest during initial fishing events that followed stocking(9.2 fish/angler hr and 18.0 fish/angler hr)and substantially declined in subsequent events(≤3.4 fish/angler hr).Catches of the newly stocked fish and previously stocked fish contributed to the high catch following the supplemental stocking.Most(80%)of the fish were caught in the first 30 min of each event and 45%were caught during the first 10 min.Anglers were able to catch 88%of the fish from the first stocking and 67%from the second stocking at least once.No mortality occurred during the study as all fish were recovered when the pond was drained.Our results suggest that hybrid sunfish will potentially provide high initial catch rates following stocking into community ponds,but managers should expect reduced catch rates following initial fishing even without harvest.Additional stocking will be needed to provide periodic increases in angler catch rates even without harvest.展开更多
Establishing suitable salt tolerant all-male tilapia strains with fast growth rate is a crucial requirement for successful euryhaline farming required for controlling prolific breeding and as an adaptation to the effe...Establishing suitable salt tolerant all-male tilapia strains with fast growth rate is a crucial requirement for successful euryhaline farming required for controlling prolific breeding and as an adaptation to the effect of climateinduced drought.This study assessed the percentage of tilapia male hybrids,their growth performance and survival rate produced by crossing female Nile tilapia(Oreochromis niloticus)and male Rufiji tilapia(Oreochromis urolepis urolepis)at different salinities.The fingerlings were reared for 70 days in triplicate concrete tanks(1 m3),each stocked with 15 fish weighing 1.62±0.03 g,1.69±0.02 g and 1.41±0.06 g exposed to 2,15 and 35 ppt salinities,respectively.Acclimatization was done by adding seawater to freshwater at a rate of 2 ppt per day for 18 days.Fish sexing was done by visual assessment of the genital papilla followed by rearing the hybrids for six months to observe reproduction.Results showed that,the cross between O.niloticus(female)and O.urolepis urolepis(male)produced hybrids that were all-males without any reproduction within six months post hybridization.The hybrids reared at a salinity of 2 ppt had higher growth performance than those reared at 15 and 35 ppt.Similarly,hybrids cultured at 15 ppt had significantly higher growth performance than those reared at 35 ppt.All the hybrids produced had survival rates of 100%.This study indicated that,all-male tilapia produced by crossing between O.niloticus(female)and O.urolepis(male)can be used by fish farmers as alternative species for mariculture development to control prolific breeding and as an adaptation strategy to climate change.展开更多
文摘The effects of transient acid spikes on development of Lepomis sunfish were studied by combining field work with laboratory studies. Lepomis sunfish eggs were collected from rocks on nests in two freshwater ponds and tested for their resistance to laboratory induced transient acid spikes. Fertilized eggs on rocks within the same nest were used for each pH transient experiment. Egg masses on one rock from the nest were used as a control while egg masses on another rock were exposed to transient acid spikes. Various stages of development showed different responses to the acidic effects. The major stages studied were fertilized egg, hatched with attached yolk sac, and free swimming with gills. The acid sensitivity followed development stages with the most acid sensitive stage being free swimming with gills. This fieldwork-laboratory data chain supports earlier field studies, providing the final link in an evidentiary chain showing the effects of transient acid spikes on Lepomis hatching profiles in freshwater ponds.
文摘Hatcheries are frequently called upon to produce catchable-sized fish for stocking community fishing ponds.Desirable attributes of fish selected for stocking into community ponds are that they are easy to produce in a hatchery system to sizes anglers are interested in catching and they provide anglers with high catch rates once stocked.Hybrid sunfish[male Bluegill(Lepomis macrochirus)×female Green Sunfish(L.cyanellus)]have attributes that potentially make them attractive for use in community fishing ponds.We assessed initial angler catch rates of 100 stocked hybrid sunfish in a 0.12-ha hatchery pond and after being subjected to angling(four,1-hr catch-and-release fishing events with five anglers).We also investigated whether catch rates would change following a supplemental stocking of an additional 100 hybrid sunfish(four,1-hr catch-and-release fishing events with five anglers).The anal fin of each fish in the second stocking was hole punched to differentiate them from those of the first stocking and fish caught by anglers were hole punched in the caudal fin each time they were caught before being released back into the pond.Angler catch rates were highest during initial fishing events that followed stocking(9.2 fish/angler hr and 18.0 fish/angler hr)and substantially declined in subsequent events(≤3.4 fish/angler hr).Catches of the newly stocked fish and previously stocked fish contributed to the high catch following the supplemental stocking.Most(80%)of the fish were caught in the first 30 min of each event and 45%were caught during the first 10 min.Anglers were able to catch 88%of the fish from the first stocking and 67%from the second stocking at least once.No mortality occurred during the study as all fish were recovered when the pond was drained.Our results suggest that hybrid sunfish will potentially provide high initial catch rates following stocking into community ponds,but managers should expect reduced catch rates following initial fishing even without harvest.Additional stocking will be needed to provide periodic increases in angler catch rates even without harvest.
文摘Establishing suitable salt tolerant all-male tilapia strains with fast growth rate is a crucial requirement for successful euryhaline farming required for controlling prolific breeding and as an adaptation to the effect of climateinduced drought.This study assessed the percentage of tilapia male hybrids,their growth performance and survival rate produced by crossing female Nile tilapia(Oreochromis niloticus)and male Rufiji tilapia(Oreochromis urolepis urolepis)at different salinities.The fingerlings were reared for 70 days in triplicate concrete tanks(1 m3),each stocked with 15 fish weighing 1.62±0.03 g,1.69±0.02 g and 1.41±0.06 g exposed to 2,15 and 35 ppt salinities,respectively.Acclimatization was done by adding seawater to freshwater at a rate of 2 ppt per day for 18 days.Fish sexing was done by visual assessment of the genital papilla followed by rearing the hybrids for six months to observe reproduction.Results showed that,the cross between O.niloticus(female)and O.urolepis urolepis(male)produced hybrids that were all-males without any reproduction within six months post hybridization.The hybrids reared at a salinity of 2 ppt had higher growth performance than those reared at 15 and 35 ppt.Similarly,hybrids cultured at 15 ppt had significantly higher growth performance than those reared at 35 ppt.All the hybrids produced had survival rates of 100%.This study indicated that,all-male tilapia produced by crossing between O.niloticus(female)and O.urolepis(male)can be used by fish farmers as alternative species for mariculture development to control prolific breeding and as an adaptation strategy to climate change.
