Background Information

• The Lake Nighthorse ecosystem development began in May, 2009 as water was pumped from the Animas River behind a newly constructed dam and reached desired water capacity in June, 2011.

• The water surface is currently 1,500 acres within the 5,500 acres of total reservoir area.

• Stocking of lake fish populations by Colorado Parks and Wildlife began in 2010 and now contain populations of disease resistance strain of Rainbow Trout (Oncorhynchus mykiss), Kokanee Salmon (Oncorhynchus nerka), and Brown Trout (Salmo trutta).

• Annually 75,000 Kokanee are stoked in Lake Nighthorse• As lake Nighthorse is a new ecosystem and still under

development it provides a unique opportunity to access the development of plankton production, aquatic and shoreline vegetation, fish populations, and interaction of trophic levels.

Purpose • The purpose of this project is to research and observe

current monitoring and wildlife management procedures through volunteer participation on a Colorado Parks and Wildlife Kokanee spawning project.

• Identify areas in which baseline ecological monitoring techniques could be implemented to increase knowledge of lake ecosystem health and development.

ConclusionsKokanee Spawning Season:• As 2014 spawning collection was the first generation of

Salmon to be raised in lake horse the overwhelming number of spawns suggests the initial stocked population was successful in surviving to maturity.

• The size of the Nighthorse Kokanee being smaller in comparison to the healthy baseline population in Lake Vallecito further advocates for increased baseline monitoring of available resources.

• In addition greater data collection of morphological characteristics would allow increase comparison capabilities to both local and statewide populations.

Current Monitoring Procedure:• Monitoring practices which are being implemented on

Lake Nighthorse are minimal and are designed primarily to meet EPA environmental quality regulations.

• An opportunity to study the full development of a lake ecosystem is being neglected, in part contributed to the lack of a management system due to stakeholder conflict.

• As with many projects, the funding necessary to conduct increased monitoring is not available, which limits the resources of agencies, such as CO Parks and Wildlife, to conduct more extensive data collection and baseline monitoring.

Proposed Monitoring:• The lake’s placement within a previously protected

wildlife area also presents opportunity to investigate the effects on decreased area of the present migration corridor, but also the increased littoral habitat and water access for many avian and mammalian species.

• Increased monitoring of water quality, especially in reference to plankton production will allow for greater knowledge of the carrying capacity limitations and better inform fisheries stocking management strategies.

• Changes in vegetation are vital to the introduction and presences of terrestrial ecosystem species .

• A comprehensive baseline monitoring approach will allow for changes in the ecosystem once public recreation is allow to be better understood and monitored.

Animas La Plata Water Conservance Distric. (2011). Lake Nighthorse Recreation Master Plan. Durango, CO: DHM Design.

Mazumder, A., & Edmundson, J. A. (2002). Imact of fertilization and stocking on trophic interactions and growth of juvenile sockeye salmon (Oncorhynchus nerka). Canadian Journal of Fish Aquatics , 1361-1373.

Smith, J. A., Baugartner, L. J., Suthers, I. M., Ives, M. C., & Taylor, M. D. (2012). Estimating the stocking potential of fish in inpoundements by modelling supply and steady-state demand. Freshwater Biology, 1482-1499.

Acknowledgements

References

A special thanks to Jim White, Pete Deren, and Mike Japhet of Colorado Parks and Wildlife for the opportunity to volunteer on this project. Your patience and detailed responses to my questions as well as the training provided is greatly appreciated. In addition I would like to thank Dr. Heidi Steltzer and Kami Parish-Larson of Fort Lewis College for providing information regarding monitoring techniques, and equipment.

An Observation of Lake Nighthorse Ecological Monitoring Accessed through a Volunteer Position with Colorado Parks and Wildlife Kokanee Spawning Project

Jenn Clayton, Environmental Biology Student

Fort Lewis College, Durango, CO

Kokanee Salmon Biology• Kokanee Salmon are a landlocked version of oceanic

Sockeye Salmon.• Kokanee are a non-predatory species and feed primarily

on zooplankton making their population carrying capacity dependent on the phytoplankton and zooplankton production of their lake habitat.

• Kokanee life span generally ranges from 3-5 years, with the majority of individuals reaching reproductive maturity and spawning at age four.

• The majority of their life is spent in cold, schooling in deep portions of the lake until sexual maturity when they swim against current into tributary rivers or creeks to spawn.

• Feeding ends several months prior to spawning in which energy is diverted to the production of eggs or sperm.

• Spawning location is dependent on site of hatching or artificial stocking due to an imprinting ability.

• At Lake Nighthorse mature Kokanee are captured using a platform (see Fig.2) with a lead net line connected to the shore.

• Stocking of Kokanee occurs at the boat ramp adjacent to the platform, which lead to the salmon imprinting on this area of the lake as spawning habitat, although no tributary exists.

• Requirements of spawning habitat for successful natural reproduction includes the movement of clean, highly oxygenated water over fertilized eggs . Lake Nighthorse does not have any natural water input so spawning must be conducted artificially.

Map of Lake Nighthorse

• The shore lead line directs fish, searching for a non-existent spawning ground along the shoreline, to a maze of narrowing net channels which traps them in a 12 foot holding net (see Fig.3)

• During processing the fish are removed from the holding nets and placed into a trough with an input of carbon dioxide gas used as a sedative to make handling easier.

Figure 2: Photo of Colorado Parks and Wildlife spawning platform , located in the cove adjacent to the boat ramp.

Figure 3: Photo of the capture nets leading to the platform holding tanks.

• Once sedated Kokanee are evaluated for whether they are ready to spawn or if they are still “green” and need additional time to develop eggs/sperm. “Green” Kokanee are returned to an initial holding net until the next spawning date and are reevaluated.

• When a mature female is found, signified by a soft underbelly, eggs are harvested by using slight pressure of the lower thumb placed along the belly, starting in front of the pectoral fins and sliding back to just behind the pelvic fins in one fluid motion (see Fig. 4). It is important not to place pressure close to the vent due to the potential to collect broken eggs, which are tedious to remove from the final batch.

• After a few females’ eggs are harvested into a small pan, sperm from a male is collected in similar fashion with additional pressure placed under the pectoral fins to remove all material from the testes.

Kokanee Spawning Procedure and Data Collection

Figure 4: Photo of female egg removal technique.

• After sperm is placed onto eggs batches of the mixture are placed in a pan of filtered water which allows fertilization to take place. Fertilized eggs must be handled gently as they are extremely fragile at this stage.

• After allowing a minimum of 45 seconds for fertilization eggs are repeatedly rinsed to remove any additional biological material such as feces, plant particles, or broken eggs from the batch (see Fig. 5).

• The clean eggs are then placed in a iodine and filtered water solution for 30 minutes to disinfect and allow time for eggs to begin the hardening process.

• A constant count is maintained to record the number of female spawns, which allows an estimate of number of eggs collected to be calculated.

• After hardening, the iodine solution is decanted and eggs are poured into sterilized holding buckets of filtered water for transport (see Fig. 6).

• A solution of formalin is added to the transport containers to also acts as a disinfectant to reduce the risk of bacterial growth.

• Care is taken to gently handle fertilized eggs as the complete protective hardening process can take up to 72 hours.

• After spawning fish are retained in separate holding nets to be donated at “giveaways” in which people with a valid fishing license can receive a fish donation.

• Length data was collected from fish post spawning to use as a health check comparison to other local populations.

• A successful spawning season at Lake Nighthorse allowed CPW to fill the Durango fish hatchery to capacity and contribute to statewide Kokanee cultivation efforts.

Figure 5: Photo of fertilized Kokanee eggs being rinse in filtered water and decanted repeatedly until all unwanted material is removed

Figure 6: Photo of fertilized egg transport containers.

Monitoring of Fish Populations Current Monitoring: • Data on length (mm) was collected from the three

primary Kokanee spawning locations under the jurisdiction of the Durango office of Colorado Parks and Wildlife; Lake Nighthorse, Lake Vallecito (Grimes Creek), and McPhee Reservoir (Dolores River).

• As seen in Figure 7, Lake Nighthorse has an average length that is between averages of Kokanee from Lake Vallecito and McPhee Reservoir.

• In addition it can be see that the ranges and minimum/maximum trend size of Kokanee are constant across all three locations, suggesting that fish size range is evidence of differences in habitat quality.

Figure 7: Statistical mean analysis of Kokanee length (mm) collected from three primary Southwest Colorado habitat locations.

Proposed Monitoring: • To increase in the ability to access the overall health of the population in reference to their

location, further data collection of fish morphology is suggested.• Potential data to included weight prior to and after artificial spawning in

conjunction with length data would allow for greater statistical analysis of variance of size between populations.

• To better understand the timing of the spawning run, data could be collected on a daily basis of the number of Kokanee collected in the holding net.

• This data count would allow for a trend of spawning time to be calculated. Also greater detailed data on the amount of fish in the collection net that are returned as “green” would also inform the time of spawning and allow a concentration of spawning efforts during the peak run. This would prevent the loss of viable eggs due to over ripening.

Plankton Production and Water Quality Monitoring

• The current biological management plan outlines monitoring of BTEX compounds as well as volatile organic compounds (VOCs) to indicate pollution sources such as fuel from recreations water vehicles health. Although, publications from the USBR are not specific on timing or consistency of testing, and publication of quality results are not readily accessible to the public.

Proposed Monitoring:• Current water visibility on the lake is much clearer than expected.

• During spawning season I conducted a water clarity test from the platform using a secchi disk system. A reading was not viable due to being able to see the disk at the full depth of 21 feet, or 7 meters.

• The clarity of Lake Nighthorse suggests low phytoplankton and zooplankton production as well as low turbidity of the water.

• Further water quality testing could be conducted using Chlorophyll A as an indicator of plankton production rates .

• In additions analysis of water pollutants such as heavy metals toxins retained from the Animas River drainage could indicate whether such influences are limiting the productivity of the primary producer trophic level and subsequently limiting available resources of upper level consumers.

Shoreline Vegetation Monitoring

Current Monitoring:

Current Monitoring:• The current management plan for Lake Nighthorse by the USBR distinctly

lacks policy for monitoring the development of shoreline and riparian vegetation, as well as changes to the entire corridor with the introduction of the artificial lake.

Proposed Monitoring:• Standard species prevalence and percent ground cover sampling is

recommended to access the development of the new littoral zone. • A unique opportunity is present to study the introduction and

communization of aquatic, and or high water demand plants which will develop a change in vegetative habitat, primarily for avian species.

Figure 1: Map of Lake Nighthorse published in the 2011 Lake Nighthorse Recreaton Master Plan.