Movement by Fishes
Movement is amongst the most important of animal behaviors, because it allows animals to respond to conditions within their environment to increase growth, survival and reproductive success (Kahler et al. 2001). The scale and pattern of fish movement varies widely among species. Some of the longest and most directed movements are completed by anadromous salmonids in North America rivers or the piracema in South America as they migrate from headwater streams as young fish to the ocean and then migrate back to their natal streams as adults to spawn. Most species of stream fish do not migrate to the ocean, but instead appear to establish home ranges of various sizes and occupy those ranges for various amounts of time. Species such as smallmouth bass (Micropterus dolomieu) or green sunfish (Lepomis cyanellus) spend a majority of their time within a home pool, but do make trips to up and downstream areas (Todd and Rabeni 1989, Smithson and Johnston 1999).
The interpretation and importance of movement for these less mobile species has changed overtime. Early researchers concluded that most adult stream fishes restricted their movements to a small home range (Gerking 1959), failing to focus much attention on evidence of movement away from the home pool, with the exception of spawning runs. Researches are re-examining the premise of what is now termed the restricted movement paradigm (Gowan et al.1994), and are discovering that this paradigm is insufficient to fully define movement by stream fishes (Smithson and Johnston 1999).
Some species of resident stream fish, such as cutthroat trout (Oncorhynchus, clarki) were thought to spend their lives in 20 meter to 50 meter stream reaches (Miller 1957). However, recent studies have shown that most trout have relatively large home ranges (Young 1994 in Fausch and Young 1995) and at times move long distances (Hilderbrand and Kershner 2000). Bjornn and Mallett (1994) studied rainbow trout (Oncorhynchus mykiss), bull trout (Salvelinus confluentus) and cutthroat trout in Salmon River, Idaho and found that over several months many fish moved greater than 8 kilometers and some had moved greater than 40 kilometers. Hilderbrand and Kershner (2000) found that similar results for other species of trout indicate that large scale movement is a widespread pattern among resident stream salmonids.
In addition to salmonids, several other species were found to move more frequently than once believed. Lonrarich et al. (2000) concluded from their observation of 1800 marked fish (central stoneroller, Campostoma anomalum; striped shiner, Luxilus chrysocephalus; northern studfish, Fundulus catenatus; longear sunfish, Lepomis megalotis and smallmouth bass, Micropterus dolomieu) that movement within two Arkansas streams was a “diffusive process” with up- and downstream movement being roughly equal. Smallmouth bass moved 120 to 948 meters/day depending on water temperature (Todd and Rabeni 1989), and 100 percent of them moved out of their home pool in spring presumably to spawn. Additionally, warm water fishes that establish home ranges also spend part of their time away from their home pool; 12 percent of green sunfish (Lepomis cyanellus) and 14 percent of longear sunfish were recaptured away from their home pool (Smithson and Johnston 1999). The entire fish assemblage represented by eight species within Sagehen Creek, California was found to be mobile (Decker and Erman 1992). Species included Lahontan redside (Richardsonius egregious), Tahoe sucker (Catostomus tahoensis), speckled dace (Rhinichythys osculus), mountain sucker (C. platyrhynchus), mountain whitefish (Prosopium williamsoni), and rainbow (Oncorhynchus mykiss), brown (Salmo trutta), and brook trout (Salvelinus fontinalis). Warren and Pardew (1998, page 642) in studying fish passage at road stream crossing of small fishes in an Arkansas stream, found that culverts were “bi-directional barriers to fish movement in both seasons despite a range of flow conditions (e.g., bank-full flows).”
Recoloniztion studies have also been interpreted as evidence that stream fish movement is important for long-term population survival. In an Illinois stream, recolonization rates were tested following experimental removal of fishes from a 46 to 100 meter long section of stream using 18 warm water fishes [including cyprinids (minnows, shiners, chubs), catostomids (suckers), centrarchids (sunfishes and basses)]. Rapid recovery occurred in both abundance, (90 percent of fish abundance returned to predisturbance conditions in 100 to 270 hours), and species composition, (0.7 of its original composition) in 60 to 140 hours (Peterson and Bayley 1993). Other studies have also found rapid recolonization of streams providing further evidence for fish movement (Larimore et al. 1959, Hall 1972). Fish are thought to repopulate stream sections through short-term exploratory movement into and out of areas (Peterson and Bayley 1993), and through season migrations such as spawning runs (Larimore et al. 1959, Hall 1972).
Movement by Juvenile Fishes
Most studies of fish movement have focused on adult stream fishes; however, fry and juveniles also move. A summary by Gowan et al. (1994, page 2627) lists several studies that discuss well known movements made by resident stream salmonids, including many made by fry. Listed below are some of the reasons for movement cited by Gowan et al.(1994):
1. Passive fry dispersal with flow,
2. Active fry dispersal possibly mediated by social dominance,
3. Limited fry dispersal in closely juxtaposed habitats,
4. Specialized patterns of fry and juvenile dispersal in unique habitats, and
5. Movements related to ontogenetic shifts in microhabitat use, possibly to increase rate of food intake or avoid competition by habitat segregation.
Movements by juvenile coho (Oncorhynchus kitsuch), cutthroat trout and steelhead (Oncorhynchus mykiss) were found to be common, with a majority of juvenile fish moving upstream (Kahler et al. 2001). These authors also reported faster growth rates for juveniles that moved, indicating the importance of having access to up- and downstream areas.
Stream ecosystems are made of assemblages of fish species that vary in their scale and pattern of movement. Even some fishes that spend a majority of their time in relatively small home ranges do spend some time away from their home pool. Juvenile fishes also move both up- and down-stream. It appears that for stream fishes movement is a widespread phenomenon that increases their changes of survival and reproduction.
Life History Cycle and Movement
According to Power et al. (1988), the ability to predict the responses of organisms to changes within their environment is dependent on an understanding of their life histories. Different life history stages often have different capabilities and needs, and use different types of habitats. The use of different types of habitats is often related to increased probability of survival. For example, stream fishes often spawn as flood waters start to rise and young are deposited in upstream or lateral habitats where predation pressure is lower than it is in downstream or mainstem rivers (Welcomme 1979). Also, by having different life history stages occupy different stream locations, the vulnerability of the population as a whole to localized disturbances is reduced (Statzner 1987). Because various life history stages of stream fishes are carried out in different locations the ability to move between habitats is important.
Even for an individual species there are regional differences associated with important life history traits, such as age or size at first reproduction or timing of spawning or downstream migrations. For many stream fishes, changes in life history stage are mediated by a combination of light, temperature or flow (Power et al. 1988). Because of the importance of understanding life history cycles when predicting responses to changes in the environment, and the possible local variability in life history cycle, local fisheries biologists are the best source of information regarding movement needs related to life history cycle.
Function of Movement
Streams are dynamic systems due to frequent disturbances such as floods or landslides, and fish habitat distribution within streams is inconsistent. Under such conditions, fish that can move between patches can recolonize disturbed areas, find new, higher quality, or less competitive habitats, or can more readily avoid predation. Also, smaller populations that are prone to extinction may be dependent on movement to sustain themselves (Schaefer 2001, Brown and Kordic-Brown 1977 in Schaefer 2001). Fish movement can also support finding critical resources that change throughout the year and throughout the life cycle of fishes. Spawning, feeding and overwintering habitats are often located in different stream reaches. In addition, habitats that are suitable for fry are often not suitable for adults so fish must move as they mature. Fish movement also allows fish to avoid unsuitable or suboptimal conditions such as seasonally dewatered areas, high stream temperatures or stream flows, or elevated pollution levels.
The movement of fishes can be affected by both the physical conditions of the stream and the composition of the fish community. In a study on the movement of three cyprinids (Notropis boops, Campostoma anomalum and Cyprinella venusta) current velocity, riffle length and predation threat were found to alter movement rates. Decker and Erman (1992) found that there were interspecies differences in physical and biological characteristics that were associated with movement within the Saghen Creek, California fish assemblage. Changes in abundance indicated movement into and out of the study reach. For example, temperature affected the abundance of Tahoe sucker, decreased stream discharge increased rainbow trout abundance; and breeding affected the abundance of Tahoe sucker, Lahotan redside, and possibly mountain whitefish.
Fish Movement Summary
In general, the ability to move about the stream environment is important to the survival and reproduction of fishes. Because, the scale and pattern of fish movement varies widely among species, it is important to investigate the species and their needs before analyzing a culvert for fish passage. It is also important to reconsider concepts about limited movements of juvenile and resident stream fishes. It may not be safe to assume that juvenile fish only require downstream passage or that resident stream fish’s survival is solely dependent on a restricted home range.