Part Three:
The use of man made debris as habitat by various fish species
Fish species use habitat in different ways, dependent upon their species and the behavior there are exhibiting. For some, habitat provides benthic nesting sites in which to lay eggs or seek protection from predation. Some of these sites house solitary individuals, are communal, or even have mixed species within them. Other benthic habitat provides more exposed shelter, allowing the fish limited protection along one flank while leaving the field open for their own form of predation.
Some species, or life stages of species, prefer close protective habitat to school in as they lack the ability to evade predation in an open limnetic setting while other species, or life stages, prefer open water with only a form of protective habitat nearby. Yet other species, usually adult apex predators, require no protective habitat at all, often preferring a deeper limnetic setting for most of their existence, but some of these still require benthic habitat of some sort for spawning. All of these species make use of the natural habitat that Cultus Lake provides and many have also habituated the various forms of manmade debris that is situated throughout it.
Large structures:
Large structures provide habitat in several ways and often multiple forms of life can be found in one location. The larger natural habitat structures of Cultus Lake are solitary tree falls, tree debris from gully washes, rocks or boulders and the vertical fauna of the littoral zone. Larger manmade structures include barrels from the old marina site, vehicles, machinery, various materials from the army training areas, discarded lumber from building projects, large mooring blocks, flat plates, boards or concrete slabs and more.
Along the larger structures substrate interface, or where the object meets the bottom, den sites are often excavated by benthic species such as sculpin, catfish and crayfish. On the surface of the object, benthic species will often rest or lay in wait for a feeding opportunity or, they may inhabit cracks or crevices. If the structure is hollow small groups of juvenile fish will school in safety from predation. Above surface projections, like the lattice work of branches or the girders of a Bailey bridge, allow larger schools of fish to swim openly, yet seek protection when they feel threatened.
Small structures:
Smaller structures in Cultus Lake often serve as individual den sites for benthic dwellers which use them for nesting or sheltered protection. Naturally these are found within rocky substrates like the slopes of alluvial fans, among the roots of plants or amidst smaller tree debris. Throughout the lake, smaller manmade structures include mooring anchors comprised of old motor blocks or buckets filled with cement, small pipes, containers or pieces of building material, lost or discarded articles like tackle boxes, fins and masks and almost anything else that can be hid in or under by fish.
One unique source of small habitat structure that is often colonized by sculpin species is the common beverage container, like pop cans and beer bottles. Some of these are unstable as habitat, in the sense that they will decompose relatively quickly (like tin, aluminum and plastic); while others, like those made of glass, persist as viable habitat for decades or perhaps even for centuries. Brown glass “stubbies”, as beer bottles of the 1960’s and 70’s were called, appear to make the perfect den site for smaller sculpin species and are usually seen to be occupied by them. They provide a well-structured internal chamber for egg-laying and small entryways that are easily defended. The openings of these glass bottles are large enough for smaller sculpin, yet too narrow for crayfish or other fish, including larger predatory sculpin. Residents can often be seen resting inside the neck of such bottles with their heads protruding, keeping watch in wait of a passing meal.
While small structures like these, whether natural or man made, are currently abundant in Cultus Lake they are in danger of diminishing due to the relentless depositing of detritus upon them. Shallow alluvial slopes, open spawning sites, bottles and other bottom lying structures are all being covered over and as this process is accelerated, via eutrophication, habitat opportunities of this kind may slowly decrease to the point that pressure is put on marginalized populations. Whether current species adapt and find new habitat, whether species are displaced, or whether they disappear from some zones altogether when this happens is a question that should be considered.
Conclusion:
As governments and advocacy groups move forward with plans to intercede in the environment of Cultus Lake, careful thought should be given to what effects our actions will have on the lake as a whole, and on specific species within it. Currently, two COSEWIC (Committee on the Status of Endangered Wildlife in Canada) designated species inhabit the lake; the Cultus Sockeye Salmon (endangered) and the Cultus Pygmy Sculpin (threatened). Consideration should focus on how their habitat will be positively or negatively affected by our decisions. Equally, our effect on these particular species predators or habitat competitors should also be understood. While we may be well meaning and acting out of a desire to improve their conditions, some remediation strategies may actually result in the removal of necessary compensatory habitat structures.
When developing action plans and strategies we should focus primarily on those issues or materials that pose the greatest known potential threat, such as petroleum/chemical contamination and eutrophication. Stewardship groups may also choose to target the removal of material pollution that has the greatest potential for degradation and dispersal while minimizing the focus on esthetically displeasing, but environmentally inert debris, like glass bottles and large metal structures, until a better understanding of their habitat roles can be determined.
At the same time, more study is required to determine the habitat such species inhabit, and whether these are at risk due to the many pressures that the lakes changing makeup exerts. If these sites are at risk, we might also consider whether manmade structures, either intentionally or unintentionally provided, might create needed transitional habitat for those species.
This approach requires a discerning and mature attitude towards lake stewardship as it may provide less visual evidence of progress than simply removing all debris, which is both more immediate and apparent. The results however, will be to stop our pendulous manipulation of the aquatic environment long enough to begin to listen to, and understand, what the many species that inhabit Cultus Lake actually need us to do on their behalf.
The use of man made debris as habitat by various fish species
Fish species use habitat in different ways, dependent upon their species and the behavior there are exhibiting. For some, habitat provides benthic nesting sites in which to lay eggs or seek protection from predation. Some of these sites house solitary individuals, are communal, or even have mixed species within them. Other benthic habitat provides more exposed shelter, allowing the fish limited protection along one flank while leaving the field open for their own form of predation.
Some species, or life stages of species, prefer close protective habitat to school in as they lack the ability to evade predation in an open limnetic setting while other species, or life stages, prefer open water with only a form of protective habitat nearby. Yet other species, usually adult apex predators, require no protective habitat at all, often preferring a deeper limnetic setting for most of their existence, but some of these still require benthic habitat of some sort for spawning. All of these species make use of the natural habitat that Cultus Lake provides and many have also habituated the various forms of manmade debris that is situated throughout it.
Large structures:
Large structures provide habitat in several ways and often multiple forms of life can be found in one location. The larger natural habitat structures of Cultus Lake are solitary tree falls, tree debris from gully washes, rocks or boulders and the vertical fauna of the littoral zone. Larger manmade structures include barrels from the old marina site, vehicles, machinery, various materials from the army training areas, discarded lumber from building projects, large mooring blocks, flat plates, boards or concrete slabs and more.
Along the larger structures substrate interface, or where the object meets the bottom, den sites are often excavated by benthic species such as sculpin, catfish and crayfish. On the surface of the object, benthic species will often rest or lay in wait for a feeding opportunity or, they may inhabit cracks or crevices. If the structure is hollow small groups of juvenile fish will school in safety from predation. Above surface projections, like the lattice work of branches or the girders of a Bailey bridge, allow larger schools of fish to swim openly, yet seek protection when they feel threatened.
Small structures:
Smaller structures in Cultus Lake often serve as individual den sites for benthic dwellers which use them for nesting or sheltered protection. Naturally these are found within rocky substrates like the slopes of alluvial fans, among the roots of plants or amidst smaller tree debris. Throughout the lake, smaller manmade structures include mooring anchors comprised of old motor blocks or buckets filled with cement, small pipes, containers or pieces of building material, lost or discarded articles like tackle boxes, fins and masks and almost anything else that can be hid in or under by fish.
One unique source of small habitat structure that is often colonized by sculpin species is the common beverage container, like pop cans and beer bottles. Some of these are unstable as habitat, in the sense that they will decompose relatively quickly (like tin, aluminum and plastic); while others, like those made of glass, persist as viable habitat for decades or perhaps even for centuries. Brown glass “stubbies”, as beer bottles of the 1960’s and 70’s were called, appear to make the perfect den site for smaller sculpin species and are usually seen to be occupied by them. They provide a well-structured internal chamber for egg-laying and small entryways that are easily defended. The openings of these glass bottles are large enough for smaller sculpin, yet too narrow for crayfish or other fish, including larger predatory sculpin. Residents can often be seen resting inside the neck of such bottles with their heads protruding, keeping watch in wait of a passing meal.
While small structures like these, whether natural or man made, are currently abundant in Cultus Lake they are in danger of diminishing due to the relentless depositing of detritus upon them. Shallow alluvial slopes, open spawning sites, bottles and other bottom lying structures are all being covered over and as this process is accelerated, via eutrophication, habitat opportunities of this kind may slowly decrease to the point that pressure is put on marginalized populations. Whether current species adapt and find new habitat, whether species are displaced, or whether they disappear from some zones altogether when this happens is a question that should be considered.
Conclusion:
As governments and advocacy groups move forward with plans to intercede in the environment of Cultus Lake, careful thought should be given to what effects our actions will have on the lake as a whole, and on specific species within it. Currently, two COSEWIC (Committee on the Status of Endangered Wildlife in Canada) designated species inhabit the lake; the Cultus Sockeye Salmon (endangered) and the Cultus Pygmy Sculpin (threatened). Consideration should focus on how their habitat will be positively or negatively affected by our decisions. Equally, our effect on these particular species predators or habitat competitors should also be understood. While we may be well meaning and acting out of a desire to improve their conditions, some remediation strategies may actually result in the removal of necessary compensatory habitat structures.
When developing action plans and strategies we should focus primarily on those issues or materials that pose the greatest known potential threat, such as petroleum/chemical contamination and eutrophication. Stewardship groups may also choose to target the removal of material pollution that has the greatest potential for degradation and dispersal while minimizing the focus on esthetically displeasing, but environmentally inert debris, like glass bottles and large metal structures, until a better understanding of their habitat roles can be determined.
At the same time, more study is required to determine the habitat such species inhabit, and whether these are at risk due to the many pressures that the lakes changing makeup exerts. If these sites are at risk, we might also consider whether manmade structures, either intentionally or unintentionally provided, might create needed transitional habitat for those species.
This approach requires a discerning and mature attitude towards lake stewardship as it may provide less visual evidence of progress than simply removing all debris, which is both more immediate and apparent. The results however, will be to stop our pendulous manipulation of the aquatic environment long enough to begin to listen to, and understand, what the many species that inhabit Cultus Lake actually need us to do on their behalf.