01-17-2013, 01:09 AM
first, my apologies for typos and grammar is as I'm doing this text to speech on the phone while I drive. I would not have time to respond if I did not do it this way.
second it is my personal uneducated opinion that the perch have had a negative impact on trophy fish such as lake trout in fish late. adding that much biomass to do any system is going to change the balance. The status quo cannot continue.never the less I do said that personal opinion aside and try to look at this objectively and determine if claims made really are substantiated.
I really appreciate the additional information you gave women bobber and the links at have been posted in this thread. It has all been quite informative. however, I still do not see an answer of why? correlation does not equal causation!
I'd like to also make the point that those papers that many have referred to as studies by so many here definitely are not true studies. not even close. And I have not looked up many of the citations to determine whether those are studies or not either. I have seen several government issued papers by biologist that have been deemed to be studies by state Fish and Game, however they did not meet basic scientific thresholds and were even proven to contain false conclusions within a very short time a publication ( using the term publication very loosely as in the way of printing not that of a peer-reviewed publication). I have seen them discredited by even lay individuals that have no formal training.
I still don't see anything that evidence is the perch are the real problem they are being blamed A.D.
has anyone that has been blaming the perch at the problem considered the changes in vegetation in the lake that coincided with the changes in species constitution? I see in 1 of the papers, I think in 2003, that aquatic vegetation in Fish Lake change drastically during the eighties and into the early ninety's. it is very curious to me that perch work Epps under control for quite a few decades Intel about the time that the vegetation changed.
for the sake of you spell discussion and a lucid 18 the facts of what causes a change, I would throw out the hypothesis that the root cause of changes at Fish Lake is not the fish species introduction, but invasive aquatic plants. I don't know if that is the case or not, but can anybody else rationally understand how it is premature to blame the perch without evidence? according to 1 of the papers the Eurasian milfoil took over in the 19 eighties and early 19 nineties. this seems to coincide very well with the changes in small fish species. it very well could be that the change in aquatic vegetation from a carpet type vegetation to 1 that grows from floor to surface has allowed the perch to overcome chubs. and has prevented the lake trout from being able to forage off of fish that can now hide in more dense vegetation.
furthermore, although I have no personal understanding of the dynamics, I could see it possible that the change in vegetation has not provided as much for forage for the fish. I could hypothesize that the native in 6 in introduced in sex that would feed off of the native plants do not do as well on the Eurasian milfoil. And therefore there is not as much food for the base forage fish.
[quote wormandbobber][quote Charina]
Am I correct to assume your argument is that they outcompete the species you listed as resource takers, but do not fulfill the roll as resource givers for other established species in the lake (i.e. makinaw)?[/quote]
Yes, in fact, they haven't filled that role for the lake trout or the trophy splake. The DWR has done diet studies at Fish Lake and have not found a single perch in the stomach of any trophy lake trout...the truth is that while chubs provided an excellent food source for lakers and big splake, perch have not. So, as a result, the trophy lake trout have turned to rainbows for their food source which, obviously, has impacted the rainbow trout fishery. And, the number of trophy splake has dwindled to the point where they are virtually non-existent in the lake anymore. Why has this happened. Because perch are eating up the small chubs and very rarely venture out into open water where lake trout roam...
" The lake trout population in Fish Lake has struggled since the proliferation of yellow perch (Chamberlain and Hepworth 2002). However, recent surveys have shown an increasing trend since 1992. Fall gill net catch rates in 2009 were the highest recorded since the current monitoring program began in 1992 (Figure 15). Additionally, lake trout catch rates for both small (< 24 inches) and large (> 24 inches) fish has trended upwards since 1992 (Figure 15). This increase in population has not resulted in an increase in catch and harvest by anglers.
During 2010, anglers caught an estimated 661 lake trout, a 400% reduction from previous surveys (Table 9). Although the overall population of lake trout appears to be increasing, the number (or proportion) of small lake trout is increasing at an even faster rate. In 2009, the majority of lake trout captured (77%) were less than 24 inches TL while Chamberlain and Hepworth (2002) reported that 63% of lake trout captured were less than 24 inches TL. A review of all marked lake trout stocked in 1989 and 1991 and recaptured between 1993 and 2010 revealed a split growth curve (Figure 11). The separate or split growth curve represents two different groups of lake trout, one that was able convert to a piscivorous diet and one that was not able to make the conversion to an entirely piscivorous diet. It is apparent that a high percent of lake trout in Fish Lake do not have the resources available to reach sizes exceeding 24 inches TL. Prior to the introduction of yellow perch, Utah chubs were the most dominant food source available for lake trout in Fish Lake (Wright 1942; Hepworth and Duffield 1984). The Utah chubs provided lake trout an intermediate size forage base, easing the transition from
invertebrates to fish (Bulkley 1958). Yellow perch now dominate the niche once occupied by Utah chubs; however they do not appear to be available or utilized as forage by lake trout (Chamberlain and Hepworth 2003). Converting to piscivory is difficult for small lake trout when the most available prey choice is a catchable-sized (8-10 inches) rainbow trout.
Summer forage fish netting has shown a declining trend in Utah chub and sucker populations since 2002 (Figure 9). The decline can most likely be contributed to a large population of yellow perch. Yellow perch have been shown to prey on and out compete young-of-year fish in other Utah waters (Hepworth et al. 2004), and are most likely affecting recruitment of both Utah chubs and Utah suckers. Utah chubs are an important food source for lake trout and splake in Fish Lake (Chamberlain and Hepworth 2002) and reductions in their numbers require lake trout to find alternate food sources. The most likely results of this shift in prey source are increased predation on stocked rainbow trout and a reduction in large lake trout."
From the paper:
Angler Survey and Monitoring Results Fish Lake, Utah 2010[/quote]
[signature]
second it is my personal uneducated opinion that the perch have had a negative impact on trophy fish such as lake trout in fish late. adding that much biomass to do any system is going to change the balance. The status quo cannot continue.never the less I do said that personal opinion aside and try to look at this objectively and determine if claims made really are substantiated.
I really appreciate the additional information you gave women bobber and the links at have been posted in this thread. It has all been quite informative. however, I still do not see an answer of why? correlation does not equal causation!
I'd like to also make the point that those papers that many have referred to as studies by so many here definitely are not true studies. not even close. And I have not looked up many of the citations to determine whether those are studies or not either. I have seen several government issued papers by biologist that have been deemed to be studies by state Fish and Game, however they did not meet basic scientific thresholds and were even proven to contain false conclusions within a very short time a publication ( using the term publication very loosely as in the way of printing not that of a peer-reviewed publication). I have seen them discredited by even lay individuals that have no formal training.
I still don't see anything that evidence is the perch are the real problem they are being blamed A.D.
has anyone that has been blaming the perch at the problem considered the changes in vegetation in the lake that coincided with the changes in species constitution? I see in 1 of the papers, I think in 2003, that aquatic vegetation in Fish Lake change drastically during the eighties and into the early ninety's. it is very curious to me that perch work Epps under control for quite a few decades Intel about the time that the vegetation changed.
for the sake of you spell discussion and a lucid 18 the facts of what causes a change, I would throw out the hypothesis that the root cause of changes at Fish Lake is not the fish species introduction, but invasive aquatic plants. I don't know if that is the case or not, but can anybody else rationally understand how it is premature to blame the perch without evidence? according to 1 of the papers the Eurasian milfoil took over in the 19 eighties and early 19 nineties. this seems to coincide very well with the changes in small fish species. it very well could be that the change in aquatic vegetation from a carpet type vegetation to 1 that grows from floor to surface has allowed the perch to overcome chubs. and has prevented the lake trout from being able to forage off of fish that can now hide in more dense vegetation.
furthermore, although I have no personal understanding of the dynamics, I could see it possible that the change in vegetation has not provided as much for forage for the fish. I could hypothesize that the native in 6 in introduced in sex that would feed off of the native plants do not do as well on the Eurasian milfoil. And therefore there is not as much food for the base forage fish.
[quote wormandbobber][quote Charina]
Am I correct to assume your argument is that they outcompete the species you listed as resource takers, but do not fulfill the roll as resource givers for other established species in the lake (i.e. makinaw)?[/quote]
Yes, in fact, they haven't filled that role for the lake trout or the trophy splake. The DWR has done diet studies at Fish Lake and have not found a single perch in the stomach of any trophy lake trout...the truth is that while chubs provided an excellent food source for lakers and big splake, perch have not. So, as a result, the trophy lake trout have turned to rainbows for their food source which, obviously, has impacted the rainbow trout fishery. And, the number of trophy splake has dwindled to the point where they are virtually non-existent in the lake anymore. Why has this happened. Because perch are eating up the small chubs and very rarely venture out into open water where lake trout roam...
" The lake trout population in Fish Lake has struggled since the proliferation of yellow perch (Chamberlain and Hepworth 2002). However, recent surveys have shown an increasing trend since 1992. Fall gill net catch rates in 2009 were the highest recorded since the current monitoring program began in 1992 (Figure 15). Additionally, lake trout catch rates for both small (< 24 inches) and large (> 24 inches) fish has trended upwards since 1992 (Figure 15). This increase in population has not resulted in an increase in catch and harvest by anglers.
During 2010, anglers caught an estimated 661 lake trout, a 400% reduction from previous surveys (Table 9). Although the overall population of lake trout appears to be increasing, the number (or proportion) of small lake trout is increasing at an even faster rate. In 2009, the majority of lake trout captured (77%) were less than 24 inches TL while Chamberlain and Hepworth (2002) reported that 63% of lake trout captured were less than 24 inches TL. A review of all marked lake trout stocked in 1989 and 1991 and recaptured between 1993 and 2010 revealed a split growth curve (Figure 11). The separate or split growth curve represents two different groups of lake trout, one that was able convert to a piscivorous diet and one that was not able to make the conversion to an entirely piscivorous diet. It is apparent that a high percent of lake trout in Fish Lake do not have the resources available to reach sizes exceeding 24 inches TL. Prior to the introduction of yellow perch, Utah chubs were the most dominant food source available for lake trout in Fish Lake (Wright 1942; Hepworth and Duffield 1984). The Utah chubs provided lake trout an intermediate size forage base, easing the transition from
invertebrates to fish (Bulkley 1958). Yellow perch now dominate the niche once occupied by Utah chubs; however they do not appear to be available or utilized as forage by lake trout (Chamberlain and Hepworth 2003). Converting to piscivory is difficult for small lake trout when the most available prey choice is a catchable-sized (8-10 inches) rainbow trout.
Summer forage fish netting has shown a declining trend in Utah chub and sucker populations since 2002 (Figure 9). The decline can most likely be contributed to a large population of yellow perch. Yellow perch have been shown to prey on and out compete young-of-year fish in other Utah waters (Hepworth et al. 2004), and are most likely affecting recruitment of both Utah chubs and Utah suckers. Utah chubs are an important food source for lake trout and splake in Fish Lake (Chamberlain and Hepworth 2002) and reductions in their numbers require lake trout to find alternate food sources. The most likely results of this shift in prey source are increased predation on stocked rainbow trout and a reduction in large lake trout."
From the paper:
Angler Survey and Monitoring Results Fish Lake, Utah 2010[/quote]
[signature]