Relationships between riverine fish and woody debris: implications for lowland rivers

1999 ◽  
Author(s):  
D. A. Crook ◽  
A. I. Robertson
Keyword(s):  
Woody Debris ◽  
Fish Habitat ◽  
Reference Points ◽  
Positive Development ◽  
Lowland River ◽  
Predator Prey ◽  
Lowland Rivers ◽  
Habitat Features ◽  
Surface Areas ◽  
Riverine Fish

This paper reviews studies of relationships between riverine fish and woody debris at micro- and meso-habitat scales, and discusses the potential functions of instream structure for lowland river fish. Experimental research, mainly in North America, has identified three main functions of woody debris as microhabitat for fish in upland streams: overhead cover that decreases predation risk both vertically and horizontally; horizontal visual isolation that reduces contact between fish; and velocity refuge which minimizes energetic costs. As with habitat features in other aquatic environments, increasing spatial complexity of woody debris may modify predator–prey interactions and provide greater surface areas for the growth of prey items. Woody debris may also provide spatial reference points for riverine fish to assist them in orienting within their surroundings. Lowland rivers differ from upland streams in terms of a number of physical variables, including turbidity, depth and water turbulence. Relationships between fish and woody debris in lowland rivers are likely to rely on mechanisms different to those in upland streams. Recent initiatives involving the reintroduction of woody debris into previously cleared lowland rivers to replace lost fish habitat are a positive development for lowland river restoration. However, if woody debris reintroduction is to maximally benefit lowland river fisheries, there is a requirement for better understanding of the ecological functions of woody debris in lowland rivers.

Fish Habitat: Essential Fish Habitat and Rehabilitation

1999 ◽  
Keyword(s):  
Lake Erie ◽  
Habitat Management ◽  
Fish Habitat ◽  
Learning By Doing ◽  
Suitable Habitat ◽  
Physical Habitat ◽  
Fish Stocks ◽  
Habitat Features ◽  
Fish Habitats

<em>Abstract.—</em> The quality and quantity of habitats determine ecosystem productivity. Hence, they determine the potential fish productivity that sustains the fish harvests extractable from freshwaters and seas. Efforts to conserve and protect fish habitats are frustrated by key unanswered questions: which habitat types and how much must be protected to ensure natural self-sustaining fish stocks? Minns and Bakelaar presented a prototype method for assessing suitable habitat supply for fish stocks in Lake Erie, an analysis that can be used to address conservation issues. Here, the method is refined and extended, taking the assessment of habitat supply for pike <em>Esox lucius </em> in the Long Point region of Lake Erie as a case study. As with the previous study, much emphasis is placed on “learning by doing.” Because available inventories of habitat features are coarse and incomplete, improved guidelines for estimating habitat supply are expected from these prototype studies. The habitat supply method previously presented by Minns and Bakelaar is elaborated in three ways here: (1) the basic physical habitat assessment is derived from a remote-sensing inventory database; (2) methods of quantifying the thermal regime and integrating it with other habitat elements are examined; (3) habitat supply estimates are used in a pike population model, and pike biomass and production are simulated for the Long Point region of Lake Erie and then compared with available records. The roles of error and uncertainty are examined for all elements in the estimation and application of suitable habitat supply values. There is potential for supply measurement and analysis to guide fish habitat management.

Benthic Habitats and the Effects of Fishing

2005 ◽  
Keyword(s):  
Gadus Morhua ◽  
Atlantic Cod ◽  
Fish Habitat ◽  
Weather Conditions ◽  
Data Sets ◽  
Fish Stocks ◽  
Habitat Features ◽  
The Irish Sea ◽  
Belfast Lough ◽  
Existing Data

<strong><em>Abstract. </em><strong>Fishers have often complained that standard United Kingdom groundfish survey data do not adequately reflect the grounds targeted by commercial fishers, and hence, scientists tend to make overcautious estimates of fish abundance. Such criticisms are of particular importance if we are to make a creditable attempt to classify potential essential fish habitat (EFH) using existing data from groundfish surveys. Nevertheless, these data sets provide a powerful tool to examine temporal abundance of fish on a large spatial scale. Here, we report a questionnaire-type survey of fishers (2001–2002) that invited them to plot the location of grounds of key importance in the Irish Sea and to comment on key habitat features that might constitute EFH for Atlantic cod <em>Gadus morhua</em>, haddock <em>Melanogrammus aeglefinus</em>, and European whiting <em>Merlangius merlangus</em>. Plotted grounds were cross-checked using records of vessel sightings by fishery protection aircraft (1985–1999). A comparison of the areas of seabed highlighted by fishers and the observations made on groundfish surveys were broadly compatible for all three species of gadoids examined. Both methods indicated important grounds for cod and European whiting off northern Wales, the Ribble estuary, Solway Firth, north of Dublin, and Belfast Lough. The majority of vessel sightings by aircraft did not match the areas plotted by fishers. However, fishing restrictions, adverse weather conditions, and seasonal variation of fish stocks may have forced fishers to operate outside their favored areas on the (few) occasions that they had been recorded by aircraft. Fishers provided biological observations that were consistent among several independent sources (e.g., the occurrence of haddock over brittle star [ophiuroid] beds). We conclude that fishers’ knowledge is a useful supplement to existing data sets that can better focus more detailed EFH studies.

Harvesting at the Community Level

2020 ◽  
pp. 205-228
Author(s):  
Michael J. Fogarty ◽  
Jeremy S. Collie
Keyword(s):  
Single Species ◽  
Economic Incentives ◽  
Unintended Consequences ◽  
Community Context ◽  
Reference Points ◽  
Individual Species ◽  
Biological Interactions ◽  
Predator Prey ◽  
The Right ◽  
Technical Solutions

Most fisheries are not directed at individual species alone. Rather, in many instances, species within a community are caught together and are also part of competitive networks and food webs. Species that are caught together are subject to technical interactions. Species that compete or are connected through predator–prey interactions (or other types of interactions) are subject to biological interactions. Ignoring either of these forms of interaction in management can lead to unintended consequences. Technical solutions can help to avoid some species while targeting others, but a comprehensive solution requires creating the right economic incentives and some incidental catch is still inevitable. Accounting for trophic interactions means that biological reference points depend on the abundance of other taxa. Single-species approaches are invalid in a multispecies or community context where biological interactions are important. Technical interactions can make it impossible to achieve target exploitation rates even if biological interactions are relatively unimportant.

Managing the Impacts of Human Activities on Fish Habitat: The Governance, Practices, and Science

2015 ◽  
Keyword(s):  
Human Activities ◽  
Habitat Management ◽  
Fish Habitat ◽  
Risk Assessments ◽  
Mitigation Measures ◽  
Policy Makers ◽  
Habitat Features ◽  
Science Advice ◽  
Governance Practices ◽  
Management Approaches

<em>Abstract.</em>—The landscape for policy and management of fish habitat is changing. The historic focus on evaluating environmental impact assessments for large projects, and issuing (or not) permits for small projects is being supplanted by new expectations for habitat managers and policy makers. Many of these new expectations are rooted in the adoption of an ecosystem approach to management of diverse human activities, including fisheries, in aquatic ecosystems, combined with a growing emphasis on integrated management of those human activities, in turn aided by spatial planning and spatial management approaches in many fields. These new expectations placed on habitat managers and policy makers create the need for expanded support from a new blending of habitat and population sciences. Historically, it may have been sufficient to use science advice based on relative indices of habitat quality and carefully assembled expert opinion as the basis for many tasks in habitat policy and management. Such tools now must be augmented by much more quantitative science advice, to allow for setting operational objectives for managing habitats, assessing the quality and quantity of critical or essential habitat for protected or exploited fish populations, conducting risk assessments of projects and mitigation measures, making siting decisions about marine protected areas and other spatial zoning measures, and many other tasks in which habitat managers and policy makers must participate. Science advice now must be able to quantify the relationships between habitat features and population status and productivity, as well with community properties such as resilience and vulnerability. This advice has to capture the uncertainty in the relationships and data sources, in forms that fit comfortably into risk assessments. Tools for forward projection of the habitat consequences of management options are needed, as are tools for cost-benefit analyses of tradeoffs among different types of habitats for different groups of aquatic species. None of these analytical challenges is beyond the scope of modern statistical and modelling capabilities, and current ecological concepts. Few of them can be met by existing tools and data-bases however. Moreover, many of the conceptual approaches to aquatic habitat management have been imported from terrestrial habitat management. They may have served adequately for management of riverine and marine benthic habitats, but some of the fundamental conceptual starting points are being questioned for marine and lacustrine habitats more generally. The paper brings out both some promising opportunities and some difficult challenges for the science needed to support contemporary habitat management and policy.

Managing for Mature Habitat in Production Forests of Western Oregon and Washington

1996 ◽  
Vol 10 (2) ◽  
pp. 422-428 ◽  
Author(s):  
Elizabeth C. Cole
Keyword(s):  
Pacific Northwest ◽  
Coarse Woody Debris ◽  
Management Practices ◽  
Woody Debris ◽  
Wildlife Habitat ◽  
Low Grade ◽  
Habitat Features ◽  
Canopy Opening ◽  
Tolerant Species ◽  
Shade Tolerant Species

Standard timber management practices in the Pacific Northwest result in stands which often vary from unmanaged stands in structure and composition. Forest and wildlife managers have identified a deficit of stands in the mature (> 100-yr-old) age class that contain certain desirable wildlife habitat features. Techniques are being developed that would increase the likelihood that managed stands can produce these characteristics. The key desirable components in these stands include large (> 75 cm diam breast height) conifer trees, snags, coarse woody debris, and understory structure, including regeneration. Vegetation management techniques can facilitate development of these components within stands. Thinning the overstory, underplanting shade-tolerant species, and creating snags and coarse woody debris can be accomplished within a production forest. Maintaining shade-intolerant species requires a higher level of disturbance and canopy opening than needed for shade-tolerant species. Treatments which remove competition from shrubs and herbaceous plants may be necessary to insure growth and survival of understory regeneration. Injection of different herbicides into low-grade conifers may yield different types of snags in comparison to girdling or topping. Although much of the understory may be eliminated during future thinnings and final harvest, some of the structure will remain and could be carried over into the next rotation along with snags and large coarse woody debris. These treatments are expected to enhance mature habitats in present and future cycles with minimum impact on yield.

scholarly journals Reference points and reference directions for size-based indicators of community structure

2005 ◽  
Vol 62 (3) ◽  
pp. 397-404 ◽  
Author(s):  
Simon Jennings ◽  
Nicholas K. Dulvy
Keyword(s):  
Ecosystem Approach ◽  
Relative Magnitude ◽  
Reference Points ◽  
Management Decision ◽  
Small Fish ◽  
Medium Term ◽  
Predator Prey ◽  
Management Decision Making ◽  
History Of ◽  
Fishing Impacts

Abstract Size-based community and ecosystem metrics, such as mean body mass and the slopes of size spectra, have been proposed as indicators to support the Ecosystem Approach to Fisheries Management (EAFM). These metrics show relatively consistent responses to size-selective exploitation, and “unexploited” indicator reference points may be predicted with models of size-structured foodwebs. Whereas unexploited reference points provide a baseline for assessing the relative magnitude of fishing impacts, target or limit reference points are needed to guide management. Values for target or limit reference points are difficult to justify on scientific grounds. However, given that fishing impacts in most ecosystems need to be reduced to meet the objectives of the EAFM, we argue that reference directions provide alternative medium-term management targets. We show that the power of surveys to detect trends consistent with reference directions depends on the range of body size classes included in the analysis. Selection of different size ranges will weight metrics to respond to the release of small fish from predation, the depletion of larger individuals as a consequence of exploitation, or both. Such weightings may not be consistent over time, because the differential vulnerability of larger species, within-population changes, predator–prey relationships, and the effects of competition depend on contemporary rates of fishing mortality and the history of exploitation. The power of the surveys investigated is poor on time scales of less than 5–10 years. Therefore, size-based indicators provide better support for medium-term, rather than year-on-year, management decision making.

Characteristics and function of large woody debris in subalpine Rocky Mountain streams in northern Colorado

1995 ◽  
Vol 52 (8) ◽  
pp. 1789-1802 ◽  
Author(s):  
Ann D. Richmond ◽  
Kurt D. Fauseh
Keyword(s):  
Pacific Northwest ◽  
Woody Debris ◽  
Fish Habitat ◽  
Rocky Mountain ◽  
Large Woody Debris ◽  
Mountain Streams ◽  
Coastal Forests ◽  
The Pacific ◽  
And Function ◽  
Rocky Mountain Streams

Large woody debris has been well studied in coastal forests of the Pacific Northwest, but little is known of its role in Rocky Mountain streams. Large woody debris was measured in 11 undisturbed streams draining subalpine old-growth forests in north central Colorado to assess abundance, characteristics, and function. Although large woody debris in Colorado had smaller diameter, length, and volume than in the Pacific Northwest, its abundance and function were similar. The majority of pools (76%) were plunge and dammed pools formed by large woody debris, most of which spanned the channels perpendicular to stream flow. Smaller streams had a greater proportion of such perpendicular pool-forming pieces than larger streams. Four disturbed streams had significantly less and smaller large woody debris than undisturbed streams. Flows in larger undisturbed streams were capable of moving large woody debris, so pieces were more often located at the stream margins, oriented diagonally, or distributed in clumps than in smaller streams. Individual pools were larger and deeper in larger streams, but their size was not related to the size of large woody debris pieces forming them. Therefore, the function of large woody debris in forming fish habitat in small Rocky Mountain streams is strongly influenced by the stream's location within the watershed.

Evaluating the influence of predator–prey interactions on stock assessment and management reference points for a large lake ecosystem

2016 ◽  
Vol 73 (9) ◽  
pp. 1372-1388 ◽  
Author(s):  
Hiroyuki Kurota ◽  
Murdoch K. McAllister ◽  
Eric A. Parkinson ◽  
N.T. Johnston
Keyword(s):  
Species Interactions ◽  
Single Species ◽  
Reference Points ◽  
Management Policy ◽  
Management Approach ◽  
Lake Ecosystem ◽  
Large Lake ◽  
Ecosystem Models ◽  
Predator Prey ◽  
Results Management

Ecosystem models are thought to offer advantages over single-species models in terms of management policy analysis. This hypothesis has proven difficult to test because of underlying system complexities, coupled with short time series and minimal contrast in environmental conditions or management policies. This paper presents a Bayesian statistical catch-at-age model to compare ecosystem models and test hypotheses about the management of a recreational fishery based on a predator–prey system using a relatively simple and data-rich ecosystem in a large lake, Kootenay Lake, British Columbia, where kokanee (Oncorhynchus nerka) are the prey and piscivorous rainbow trout (Oncorhynchus mykiss) are the predator. A model that explicitly incorporates the predator–prey interaction explained long-term data of field and fishery surveys much better than single-species models without any interactions. Minimally realistic multispecies models that treated predation identically but differed in their representation of the effects of prey abundance on predator mortality produced quite different results. Management reference points, for example, differed considerably between the models. Our study thus emphasizes that the choice of a management approach for this type of fishery will depend strongly on the model form and should take into consideration results from empirically based models that include species interactions.

The effects of variable retention forestry on coarse woody debris dynamics and concomitant impacts on American marten habitat after 27 years

2020 ◽  
Vol 50 (9) ◽  
pp. 925-935 ◽  
Author(s):  
Ingrid Farnell ◽  
Ché Elkin ◽  
Erica Lilles ◽  
Anne-Marie Roberts ◽  
Michelle Venter
Keyword(s):  
Coarse Woody Debris ◽  
Woody Debris ◽  
Multiple Use ◽  
Mammal Species ◽  
American Marten ◽  
Habitat Features ◽  
Decay Class ◽  
Retention Forestry ◽  
The Impact

Coarse woody debris (CWD) in the form of logs, downed wood, stumps and large tree limbs is an important structural habitat feature for many small mammal species, including the American marten (Martes americana). At a long-term experimental trial in northern temperate hemlock-cedar forests of British Columbia, Canada, we analysed the impact of varying amounts of overstory basal area retention: 0% (clearcut), 40%, 70%, and 100% (unharvested) on CWD volume, decay class, and inputs from windthrow over 27 years. We used CWD attributes (diameter, length, decay class, and height above the ground) known to be favourable for martens to create an index for assessing the impact of harvesting intensity on CWD habitat features. Stands with 70% retention had CWD attributes that resulted in CWD habitat features similar to unharvested stands. Clearcuts contained pieces that were smaller, more decayed, and closer to the ground, which contributed to a habitat that was less valuable, compared with stands that had higher retention. Over the 27-year period, windthrown trees were the majority of CWD inputs, and volume change was positively related to percent retention. Our results highlight that forest management influences CWD size and input dynamics over multiple decades, and the need for consideration of these impacts when undertaking long-term multiple-use forestry planning.

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