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1431. [Article] A Proposal for an Integrated Research Monitoring Program for Oregon Coastal Chinook Populations
Abstract -- Among the many chinook salmon populations contributing to large, mixed stock ocean net, troll, and recreational fisheries managed by the Pacific Salmon Commission (PSC) there is a good deal ...Citation Citation
- Title:
- A Proposal for an Integrated Research Monitoring Program for Oregon Coastal Chinook Populations
Abstract -- Among the many chinook salmon populations contributing to large, mixed stock ocean net, troll, and recreational fisheries managed by the Pacific Salmon Commission (PSC) there is a good deal of diversity with respect to productivity, life history characteristics, and ocean distribution. During the years immediately following the adoption of the original 1985 Pacific Salmon Treaty (PST), lack of adequate data prevented the PSC from managing effectively for these differences. Instead, chinook management outlined in Annex IV of the original treaty was based upon long term population trends for very large aggregates of stocks. Although harvest ceilings were established as part of a PST recovery plan for over-exploited stocks, they were based on average coast-wide production trends and resulted in over harvest of weak stocks in some years and failure to take advantage of large returns in other years. By the mid-l 990's, data relative to the distribution and abundance of many salmon stocks contributing to PST fisheries was improving. At the same time, there was increasing dissatisfaction with quota-based management and strong interest in instituting annual abundance-based management for stock aggregates that share geographic proximity of spawning areas, similar life history and genetic characteristics, and similar distributions in the ocean. Abundance-based management for aggregated stocks would establish and implement annual fishery exploitation rates in fisheries that insure long-term sustainability for all aggregates and related individual stocks. In the absence of bilateral agreement between the U.S. and Canada regarding implementation of abundance-based management, the three voting U.S. PSC Commissioners signed the 1996 Letter of Agreement (LOA) that defined elements of an abundance-based management approach for chinook salmon fisheries in southeast Alaska. The LOA was designed to: 1) set the stage for future bilateral negotiations regarding abundance based management; 2) clarify the role of PST fisheries in rebuilding depressed natural stocks; and 3) provide a means for sharing conservation responsibility of far-north migrating stocks originating from watersheds in Oregon and Washington. The foundation for abundance-based management set forth in the LOA was subsequently expanded upon and incorporated as Aggregate Abundance-Based Management (AABM) in Annex IV, Chapter 3 of the 1999 PST. Application of the abundance-based management outlined in the 1996 LOA and the subsequent 1999 amendments to the PST requires knowledge of the stock recruitment relationships, biological spawning escapement goals, and annual forecasts of ocean abundance and distribution for stocks in each aggregate to regulate fishery harvest. Managers must also have annual post-season estimates of aggregate specific exploitation rates and in-river escapements to assess the effectiveness of regulatory measures. The base-monitoring program for Oregon's coastal chinook under the 1985 PSC met only a few of these data requirements. In recognition of requirements for new and more precise data, the signatories of the original LOA sought out additional federal funds for new and expanded monitoring programs. Since 1997 Congress has annually approved approximately $1.8 million for additional research and monitoring needed to implement terms of the LOA. The PSC delegated discretionary authority for the use of those funds to the U.S. Section's Chinook Technical Committee (CTC).
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Water temperature is an essential property of a stream. Temperature regulates physical and biochemical processes in aquatic habitats. Various factors related to climatic conditions, landscape characteristics, ...
Citation Citation
- Title:
- The influence of climate change and restoration on stream temperature
- Author:
- Diabat, Mousa
Water temperature is an essential property of a stream. Temperature regulates physical and biochemical processes in aquatic habitats. Various factors related to climatic conditions, landscape characteristics, and channel structure directly influence stream temperature. Numerous studies indicate that increased average air temperature during the past century has led to stream warming across the world. The trend of stream warming was also present in spring-fed watersheds, where summer flow has decreased. In addition, anthropogenic practices that alter the natural landscape and channel structure, such as forest management, agriculture, and mining contributed to stream warming. For example, deforested and unshaded stream reaches or dredged channels were warmer than shaded reaches and meandering streams. Stream temperatures in North American lotic habitats are of a specific concern due to their significant economic, cultural, and ecological value. With climate projections indicating that air temperature will only continue to rise throughout the 21st century, cold- or cool-water organisms, especially fishes, will be affected. Therefore, there is a strong need to better understand the impacts of changing climate, riparian landscape, and channel structure on a stream's heat budget. This may assist in restoring the historic thermal regime in impacted sites and mitigating the impacts of future climate change. This study looks into the relative influences of the different factors on a stream's heat budget with three manuscripts: one on stream temperature response to diel timing of air warming, one on stream temperature response to changes in air temperature, flow, and riparian vegetation, and one on stream temperature response to air warming and channel reconstruction. I used the software Heat Source version 8.05 to simulate stream temperature for all three analyses along the Middle Fork John Day River, Oregon USA. Two of the manuscripts were applied to an upper 37 km section of the Middle Fork John Day River (presented in chapter 2 and 3), where the third manuscript was applied to a 1.5-km section. The sensitivity analysis of stream temperature response to diel timing of air warming (Chapter 2: Diel Timing of Warmer Air under Climate Change Affects Magnitude, Timing, and Duration of Stream Temperature Change) was based on scenarios representing uniform air warming over the diel period, daytime warming, and nighttime warming. Uniform warming of air temperature is a simple representation of increases in the average daily or monthly temperatures generated by the 'delta method'. The delta method relies on adding a constant value to the air temperature time-series data. This constant value is the difference (delta) between base case average air temperatures and the projected one. Scenarios of daytime or nighttime warming represent conditions under which most of the warming of the air occurs during the daytime or the nighttime, respectively. I simulated the stream temperature response to warmer air conditions of +2 °C and +4 °C in daily average for all three cases of air warming conditions. The three cases of different diel distributions of air warming generated 7-day average daily maximum stream temperature (7DADM) increases of approximately +1.8 °C ± 0.1 °C at the downstream end of the study section relative to the base case. In most parts of the reach, the three distributions of air warming generated different ranges of stream temperatures, different 7DADM values, different durations of stream temperature changes, and different average daily temperatures. Changes of stream temperature were out of phase with imposed changes of air temperature. Therefore, nighttime warming of air temperatures would cause the greatest increase in maximum daily stream temperature, which typically occurs during the daytime. The sensitivity analysis of the relative influences of changes in air temperature, stream flow, and riparian vegetation on stream temperature (Chapter 3: Assessing Stream Temperature Response to Cumulative Influence of Changing Air Temperature, Flow, and Riparian Vegetation). This study summarized stream temperature simulation in 36 scenarios representing possible manifestations of 21st century climate conditions and land management strategies. In addition to existing conditions (base case) of flow, air temperature, and riparian vegetation, scenarios consisted of: two air temperature increases of 2 °C and 4 °C, two stream flow variations of +30% and -30%, three spatially uniform riparian vegetation conditions that create averages of effective shade 7%, 34%, and 79%, in addition to 14% for base case conditions. Results suggest that variation in riparian vegetation was the dominant factor influencing stream temperature because it regulates incoming shortwave radiation, the largest heat input to the stream, while variation in stream flow has a negligible influence. Results indicated that increasing the effective shade along the study section, particularly in the currently unshaded sections, could mitigate the influence of increasing air temperature, and would reduce stream temperature maxima below current values even under future climate conditions of warmer air. With the small influence it had, increasing stream flow reduced the 7DADM under low shade conditions. However, increasing stream flow showed counterintuitive results as it contributed to increasing stream temperature maxima when the stream was heavily shaded. The applied study examined the stream temperature response to restoration practices and their potential to mitigate the influence of warmer air conditions (Chapter 4: Estimating Stream Temperature Response to Restoring Channel and Riparian Vegetation and the Potential to Mitigate Warmer Air Conditions). This study focused on a 1.5 km section along the upper part of the Middle Fork John Day River that was modified due to past anthropogenic activities of mining for gold and timber harvest. Currently, the riparian vegetation of the study site is mostly shrubs and stands of short trees. Restoration designs call for the restoration of both the channel structure and replanting the riparian vegetation. Simulation results showed that the 7DADM was higher in the restored channel than the existing channel with both conditions of low and high effective shade conditions. However, a combined restoration practice of channel reconstruction and medium effective shade conditions reduced stream temperature maxima more than restoring riparian vegetation alone. In addition, results showed that restoring riparian vegetation was sufficient to mitigate the influence of warmer air on stream temperature, while restoring the channel alone is not. Heat budget analysis showed that heat accumulation during the daytime increased in the restored channel, which was longer, narrower, and deeper than the existing channel. It is important to emphasize that stream temperature is one of many goals that restoration activities aim to improve. Furthermore, differences in 7DADM among the different scenarios of restoration are negligible. Such small differences could hardly be measure. While this study examined a short section of 1.5 km, longer stream sections may increase the differences in 7DADM. Primary conclusions of this study are: 1) daily maxima of stream temperature will increase in response to increased air temperature regardless of the distribution of air warming during the diel cycle; 2) nighttime air warming caused a greater increase in stream temperature maximum than daytime warming; 3) riparian vegetation was the dominant factor on stream's heat budget, more than air temperature or stream flow; 4) restoring riparian vegetation mitigated the influence of warmer air; 5) restoring channel structure alone was not sufficient to lower temperature maxima; and 6) restoration project was most successful in improving degraded stream temperature when combined with channel reconstruction and improved riparian shade.