Roger G. Young

Organic matter breakdown and ecosystem metabolism: functional indicators for assessing river ecosystem health

Abstract River health monitoring traditionally has made use of structural measurements (water quality or taxonomic composition of aquatic organisms). We argue that a more complete assessment of river health should include functional metrics, such as rates of organic matter decomposition and ecosystem metabolism. Leaf breakdown links the characteristics of riparian vegetation with the activity of both aquatic invertebrates and microbial organisms and is affected by natural and human-induced variation in a wide range of environmental factors. Measurement of leaf breakdown is relatively simple and has modest equipment requirements. River metabolism (gross primary productivity and ecosystem respiration) measures the rates of production and use of organic C in river ecosystems as a whole, providing a direct estimate of the food base that determines life-supporting capacity. Metabolism measurements require more sophisticated equipment than do measurements of leaf breakdown, but improvements in technology have made metabolism measurements relatively easy. We review the factors that influence leaf breakdown and river metabolism and pay particular attention to the effects of human-induced environmental stressors. We also describe how measurements can be standardized and suggest criteria for interpreting functional measures in terms of river ecosystem health. Last, we consider the strengths and weaknesses of both methods as functional measures and provide recommendations for their use as biomonitoring tools.

Water quality impact of a dairy cow herd crossing a stream

Abstract The water quality impact of a herd of 246 dairy cows crossing a stream ford was documented. Two cow crossings produced plumes of turbid water associated with very high concentrations of faecal indicator bacteria (Escherichia coli) and high suspended solids (SS) and total nitrogen (TN). On the first crossing, towards the milking shed, the cows were tightly‐bunched and produced a sharp spike of contamination (E. coli peaking at 50 000 cfu/100 ml). After milking, the cows wandered back across the stream as individuals or small groups, and contaminants were less elevated, albeit for a longer period. Light attenuation, measured continuously by beam transmissometer, correlated closely with E. coli, SS, and TN, permitting the total yield of these contaminants to be estimated. Contaminant yields for the two crossings were very similar, suggesting that time taken and whether or not cows are herded may not greatly influence water quality impact. The cows defecated c. 50 times more per metre of stream crossing than elsewhere on the raceway. This study has shown that cattle accessing stream channels can cause appreciable direct water contamination, suggesting that excluding cattle from streams will have major water quality benefits.

Water quality and thermal regime of the Motueka River: Influences of land cover, geology and position in the catchment

Abstract We examined the effects of land use, geology, and longitudinal position within the river network on water quality and thermal regime at 23 sites within the Motueka River catchment. The concentrations of suspended solids, nitrate nitrogen, total nitrogen, Escherichia coli, and Campylobacter were higher at sites draining pastoral and horticultural land than in similar‐sized native or plantation forest streams. Average daily mean temperature and minimum temperature in summer and maximum winter temperature were higher in unshaded pastoral and horticultural streams than at native forest sites. Differences in water quality and thermal regime were also observed among sites with contrasting geology. Conductivity, pH, and minimum winter temperatures were highest at sites draining marble terrain. In contrast, longitudinal patterns in water quality and temperature regime along the 120‐km length of the river were relatively weak, although longitudinal patterns in amplitude of daily temperature fluctuation matched theoretical predictions. In this study, differences in land use appeared to have the strongest influence on most water quality and thermal variables examined. However, geology was an important factor explaining variation in certain variables (e.g., pH and conductivity). Longitudinal patterns in water quality and temperature were relatively weak and in many instances were linked with longitudinal patterns in land use and geology rather than catchment location alone.

Linkages between cultural and scientific indicators of river and stream health

Scientific monitoring of river health is well established and has a significant role to play in environmental assessment by communities, managers and policy makers. Cultural indicators help to articulate cultural values, assess the state of the environment from a cultural perspective and assist with establishing a role for Māori in environmental monitoring. We reviewed the philosophies behind cultural and scientific monitoring of river health and compared the results from the two approaches at 25 sites in the Motueka and Riwaka catchments. Both scientific and cultural indicators suggested a decrease in river health in relation to increased land-use pressure. There were also correlations between the results from the two approaches suggesting cultural indicators could be used in a similar manner as scientific indicators to set environmental benchmarks. Using scientific approaches alongside culturally based monitoring provides a wealth of knowledge to understand better what we mean by river health. The two approaches can be regarded as complementary and reflect two different knowledge systems and perspectives.

Movement and Mortality of Adult Brown Trout in the Motupiko River, New Zealand: Effects of Water Temperature, Flow, and Flooding

Abstract Management of the effects of water quality and flow on fisheries requires an understanding of the factors that control fish movements. We used radiotelemetry to monitor the movements of adult brown trout Salmo trutta in a New Zealand river over 11 months (September 2004 to August 2006) and linked those movements to the changes in flow and water temperature. Individual fish moved up to 41 km during the study. However, most fish moved less than 1 km. All of the trout that showed little movement throughout the summer were living in relatively deep pools that presumably provided cover. The rates of movement declined steadily over the spring–summer period, as flow decreased and water temperature increased. The percentage of fish moving was positively related to the average daily flow during the interval between tracking occasions and negatively related to the average daily water temperature, less than 20% of the tagged fish moving once temperatures were above 19°C. A severe, 50-year flood occurred in ...

Angling Pressure and Trout Catchability: Behavioral Observations of Brown Trout in Two New Zealand Backcountry Rivers

Abstract Angling pressure is increasing in many recreational trout fisheries throughout the world. There is a strong perception among anglers that trout become harder to catch after being disturbed by other anglers, thus affecting the quality of their angling experience. However, there is little scientific evidence to support or refute this perception. We measured the response to angling pressure in two rivers in New Zealand: The remote Ugly River and the more heavily fished Owen River. Both of these rivers have fisheries for brown trout Salmo trutta. The numbers of trout seen and caught over the length of four 3-d angling trips were compared between rivers. The behavioral responses to angling of naive trout in the Ugly River were compared with those of Owen River trout and trout that had been angled previously from the Ugly River. The proportion of the trout population in the study reaches caught by two anglers after four 3-d trips was estimated as between 11% and 23% in the Owen River and up to 47% in t...

Integrated catchment management—interweaving social process and science knowledge

This paper provides an overview of the Motueka integrated catchment management (ICM) research programme. This research was based on the thesis that achieving ecosystem resilience at a catchment scale requires active measures to develop community resilience. We define a generic adaptive planning and action process, with associated knowledge management and stakeholder involvement processes, and illustrate those processes with observations from five research themes: (1) water allocation; (2) land use effects on water; (3) land and freshwater impacts on the coast; (4) integrative tools and processes for managing cumulative effects; and (5) building human capital and facilitating community action. Our research clearly illustrates the benefits for effective decision-making of carrying out catchment scale science and management within collaborative processes which patiently develop trusting relationships. We conclude that coastal catchments should be managed as a holistic continuum from ridge tops to the sea and that some processes like floods or loss of community resilience have decadal consequences, which support the need for long-term monitoring and investment.

Factors affecting juvenile galaxiid fish passage at culverts

Alteration of urban streams by culverts is common throughout the world and is known to impede freshwater fish movement. The main objectives were therefore to investigate how different culvert characteristics (e.g. height, length, angle, perched v. non-perched) and habitat variables (e.g. water velocity, riverbed gradient) affect the passage success of juvenile inanga (Galaxias maculatus), a weak-swimming migratory fish. We determined whether passage of juvenile G. maculatus could be improved by installing a ramp at thirteen replicate in situ culverts in Nelson City, New Zealand. As expected, none of the 400 fish tested were able to pass undercut (i.e. perched) culverts before ramp installation (0% passage), compared with the 250 fish (65% passage) that were able to pass non-perched culverts. Significantly more fish (44% passage) reached perched culvert outlets when aided by the ramp. Passage success with the ramp depended on its length and angle, with fewer fish passing longer or steeper ramps. To provide upstream passage for weak-swimming species such as juvenile (fork length < 60 mm) G. maculatus, ramp length and angle should not exceed three metres and 20 degrees, respectively. With passage requirements known and mitigation processes in place, urban fish populations might be able to be sustained.

Building collaboration and learning in integrated catchment management: the importance of social process and multiple engagement approaches

Success at integrated catchment management (ICM) requires the ongoing participation of different stakeholders in an adaptive and learning-based management process. However, this can be difficult to achieve in practice because many initiatives fail to address the underlying social process aspects required. We review emerging lessons around how to engage stakeholders in ways that support social learning. We focus on the experience of an ICM research programme based in the Motueka catchment in New Zealand and provide a simple framework for distinguishing a range of conversations across different communities of practice. We highlight the need to use multiple engagement approaches to address different constituent needs and opportunities, and to encourage the informal conversations that spring up around these. We then illustrate the range of platforms for dialogue and learning that were used in the programme during 10 years of ICM research. Finally, a number of lessons are described from across the programme to guide research leaders and managers seeking to improve collaboration in other integrated science, management and policy initiatives.

Suitability of Dual-frequency Identification Sonar (DIDSON) to monitor juvenile fish movement at floodgates

The effects of coastal floodgates on fish distribution are largely unknown. In this study, we used Dual-frequency Identification Sonar (DIDSON) to assess the effect of tidal floodgates on movement of diadromous juvenile galaxiids in a New Zealand estuarine system and test the suitability of DIDSON as a tool for monitoring behaviour of small fish. DIDSON allowed observations of juvenile galaxiid movements over 24 h through contrasting gated and un-gated culverts. More than twice as many fish were recorded passing the un-gated culvert than the gated culvert. Movement occurred during the day and night and was highest at the un-gated culvert just before high tide. By contrast, movement past the gated culvert was highest during low tide, when the gate was open. DIDSON is suitable for discretely observing in situ behaviour of small fish at night or in turbid water and will assist to identify design and operational needs for fish-friendly floodgates.