Disturbance and Fish Daniel D. Magoulick USGS, Arkansas Cooperative Fish & Wildlife Research Unit, Department of Biological Sciences, University of Arkansas

Disturbance Two ways to define disturbance Effects on organisms “any relatively discrete event that removes organisms and opens up space and other resources that can be used by individuals of the same or different species.” (Townsend and Hildrew 1994) Response to event is part of definition Response must occur Difficult to compare among systems Physical nature of event Defined by the nature of their damaging properties, especially intensity, frequency, predictability, spatial extent and temporal duration Response to disturbance is examined separately

Types of Disturbance Pulse – short-term, sharply delineated Floods Non-persistent pollution Press – arise sharply, reach constant level Sedimentation after fire Dam building Persistent pollution Ramp – steady increase in time, may level off Drought

Perturbation Types Perturbation – combo of cause and effect related to disturbance

Response to Disturbance Resistance – ability of the community to avoid displacement by disturbance Resilience – ability of community to return to its former state after disturbance

Drought as Disturbance

Two types of Drought Seasonal – drying in a particular season(s) Predictable Periodic or regular Supra-seasonal – drying over multiple seasons unpredictable

Perturbation Types During Drought Seasonal press disturbance and response Supra-seasonal Ramp disturbance and response

Factors Affected by Drought

Questions What factors are most important in determining fish and crayfish assemblage structure in drying streams? What habitats act as refugia and how does refuge use influence fish and crayfish assemblage structure in drying streams?

Questions What habitats act as refugia during stream drying? Hyp: Pools act as refugia  Net migration into pools Does stream drying lead to a concentration effect? Hyp: Reduced area and fish migration increase densities in pool habitats (refugia) Hyp: Reduced area and fish migration lead to unchanged densities in riffle/run habitats 3km

YOY Central Stoneroller July Pool Sept Riffle

Conclusions Survival rates were low and species-dependent. Refuge habitats are species and size-dependent Pools  Adult creek chubs and central stonerollers Riffles  YOY central stonerollers and bigeye shiners Reduced habitat area and fish migration led to increased densities

Logitudinal Drying Patterns Dowstream drying Headwaters drying Mid-reach drying

Questions How do fish use intermittent streams? What factors affect fish movement between mainstem and intermittent tributary? Can intermittent streams act as spawning and nursery areas?

Methods From 24 March through 3 July 2003, smallmouth bass were collected in the Buffalo River and Bear Creek using an electrofishing boat, barge, or backpack.

…with the antenna passing through the incision and trailing externally alongside the body. Average time out of water for bass was <10 min Bass were then transferred to recovery tanks of non-treated water after surgery and their condition was monitored until they regained equilibrium and exhibited strong gilling behavior Bass were then released to their points of capture

Results 59 marked bass Buffalo River 324 – 445 mm 480 – 1000+ g Bear Creek 319 – 403 mm 452 – 1000+ g Total of 59 bass were tagged throughout the lower 30 km of Bear Creek and pools of the Buffalo River near the confluence with Bear Creek Buffalo River bass ranged 324 – 445 mm in length and 480 – >1000 g in weight Bear Creek bass ranged 319 – 403 mm in length and 452 – >1000 g in weight

Stream-use categories Buffalo River residents 24 Bear Creek residents 23 Using both streams 12 Similar numbers of bass were found to be residents of their tagging stream and about a quarter of telemetered bass used both streams In the background is a smallmouth bass that was re-captured one year after surgery

Smallmouth Bass Locations

Smallmouth Bass Movers

Kernel density estimate (km) “Summer” Home Range Kernel density estimate (km) Category N 95% 90% 50% Buffalo resident 8 0.74 A 0.66 0.10 Bear resident 6 0.28 0.03 Using both 10 3.25 0.05 Median linear home range sizes during “summer” period for smallmouth bass radio-tracked in the Buffalo River and Bear Creek by stream-use group. Tukey’s studentized multiple-range tests were used to evaluate differences in means; values with a letter in common are not significantly (P < 0.05) different

“Entire Study” Home Range Kernel density estimate (km) Category N 95% 90% 50% Buffalo resident 4 15.40 AB 11.17 0.22 A Bear resident 4.17 2.87 0.32 Using both 36.32 B 30.41 Median linear home range sizes during “entire study” period for smallmouth bass radio-tracked in the Buffalo River and Bear Creek by stream-use group. Tukey’s studentized multiple-range tests were used to evaluate differences in means; values with a letter in common are not significantly (P < 0.05) different

Conclusions Smallmouth bass use intermittent portions of Bear Creek. Summer drying events appear to limit bass movement. Immigration of fish into Bear Creek can be substantial Spawning migrations Larval fish drift densities are very high in Bear Creek Substantial in intermittent portion of stream

Otolith Microchemistry What are otoliths? Application of microchemistry Relationship with water Advantages and disadvantages I used otolith microchemistry to corroborate my telemetry work to describe movements of smallmouth bass in the same system Despite the useful data that are gathered using telemetry techniques, these studies may be expensive and labor intensive Microchemistry of hard parts of fish, an indirect procedure that can be used to investigate life histories of fish, is being applied increasingly to determine origins and movement patterns of fishes Otoliths are chemically stable and provide an accurate permanent record of environmental histories for individual fish Although analysis of scales has been used in microchemistry studies, evidence suggests that scales may cease growing or be resorbed during times of physiological stress and scale chemistries have been found to be more variable and discrimination of known-origin fish to be poorer than with otoliths Otoliths are able to record information about fish movement because of the physical processes involved in their formation. Calcium carbonate (CaCO3), protein, and inorganic elements precipitate out of the endolymphatic fluid and crystallize onto the surface of the otoliths causing a continuous accretion of layers (Campana and Neilson 1985). Chemical composition of otoliths has been found to directly correlate with the aquatic environment However, elemental incorporation into the otolith is not a simple function of environmental availability

Elemental Discrimination Elemental discrimination occurs as elements from the water pass into the blood plasma via the gills or intestine, cross from the plasma to the endolymph, and crystallize onto the otolith Most element:Ca ratios in the otolith are far lower than those in the blood plasma or ambient water because of the discrimination that occurs Variation in otolith elemental signatures can also be affected by water temperature and salinity, however, the effects ambient temperature and salinity have on otolith chemistry are thought to be minimal compared with the influence of ambient Ba:Ca Figure gives an overview of elemental pathways and barriers between seawater and otoliths, with coarse estimates of transfer rates for Ca, Sr, and Ba at each physiological barrier Water passing over the gills is the primary source of most elements in freshwater fish; 80 to 90% of Ca and Sr are derived from the water with freshwater fish A small but unknown proportion of elements is undoubtedly assimilated from food sources, however, experiments have suggested that otolith uptake of a suite of minor elements from food was minimal Elemental concentrations are referenced to calcium because the initial uptake of many elements is often inversely proportional to the relative calcium concentration

Objectives Determine temporal stability and spatial variability of elemental signatures in Bear Creek and Buffalo River Associate water chemistry from Bear Creek and the Buffalo River with otolith chemistry in resident fish Use otoliths to describe previous locations of fish within Bear Creek and the Buffalo River Previous otolith microchemistry work indicates that it is possible to effectively describe fish movement within a river basin and may be applicable at finer resolutions Although chemical gradients may not be as pronounced in freshwater systems, certain elements vary across freshwater environments (e.g., Mg, Mn, Ca, Sr, and Ba) and have been used to describe fish movement wholly within freshwaters My objectives were to (1) determine if temporal stability and spatial variability in elemental signatures existed among Bear Creek, the Buffalo River, and surrounding tributaries; (2) associate water chemistries from Bear Creek and the Buffalo River with corresponding sites on otoliths; and (3) use chemical signatures from otoliths to describe fish location within Bear Creek and the Buffalo River during previous years.

The Buffalo River and Bear Creek pass over a variety of rock types The Buffalo River flows northeast through the Springfield Plateau and borders the northern edge of the Boston Mountains Plateau As it flows downstream it goes from a shale, limestone, and chert environment to a sandstone, limestone, and dolomite environment Bear Creek crosses the transition zone between the Springfield and Boston Mountain plateaus and passes over several different soil types: the headwaters are located in a mixture of limestone and shale substrates, the middle reach flows through limestone, and the substrate of the lower reach is mostly karst Shale is known to sorb and hold heavy metals to a larger extent than other sedimentary rock Higher concentrations of calcium and magnesium are typically found in limestone and dolomite I conducted water sampling from October 2003 through April 2005 on eight separate occasions at 4 primary collection sites: upper, middle and lower Bear Creek and an additional site on the Buffalo River downstream of the confluence with Bear Creek Secondary sites within Bear Creek, the Buffalo River and surrounding tributaries were sampled during August 2004 to evaluate spatial variation in water chemistry For each water sample, 60 mL of stream water was filtered through a 0.45-μm filter using a syringe and acidified to pH <1 by adding 1 mL ultrapure nitric acid for preservation Metal concentrations of the water samples were measured by dynamic reaction cell inductively coupled plasma mass spectrometry I collected smallmouth bass from 29 July through 28 August 2004 using backpack electrofishing equipment at primary water sampling sites. I collected fish at this time because discharge within Bear Creek and the Buffalo River was low for several weeks prior to sampling and I assumed that recent fish movement was minimal based on the presence of dry stream channels, therefore otolith signatures would reflect the chemical signature in the water at the site of capture

Methods Collected water samples October 2003 – April 2005 Analyzed chemical concentrations of water Collected smallmouth bass August 2004 Extracted otoliths

Otolith Ablation Otoliths were analyzed using laser ablation-inductively coupled plasma-mass spectrometry The laser was used in spot mode to ablate four 50-μm craters at the otolith core as well as edge (summer 2004), edge-1 annulus (summer 2003), and edge-2 annuli (summer 2002) Two images of the same polished thin section of sagittal otolith from a smallmouth bass collected in the middle reach of Bear Creek, Arkansas. A transmitted light photomicrograph (a) reveals the core and annuli, while a surface illuminated image (b) shows the ion probe craters (~50 μm in diameter). Ablated material was carried to the ICP-MS by a 1-l/min flow of argon gas Approximately 15 s of ablation data were averaged for every shot, the four shots were averaged for each summer growth band or core sample, and the average count rates were used to produce concentrations (ppm) for each element that were converted to element:Ca ratios (mmol/mol). Concentrations were determined by comparing the element:Ca ratio from the otoliths to United States Geological Survey carbonate standard MACS-1, which was ablated before shooting groups of 5–10 otoliths. I calculated the same element:Ca ratios for otoliths that had been measured for the water samples.

Data Integration Raw counts from the ICP-MS were processed off line using a spreadsheet-based macro; 29 analytes were recorded, Ca44 is the most abundant… Background subtracted counts on individual elements were compared to the mean count rate for that element by bracketing the gas blank, sample signal plateau and the matrix following ablation Approximately 15 s of ablation data were averaged for every shot, the four shots were averaged for each summer growth band or core sample, and the average count rates were used to produce concentrations (ppm) for each element that were converted to element:Ca ratios (mmol/mol)

…I used Pearson’s correlation analyses to determine whether or not the ratios were correlated Scatter plot of the Ba:Ca concentrations in water and smallmouth bass otoliths indicated that they were directly related to one another Buffalo River (circles; N = 8), lower (triangles; N = 13), middle (squares; N = 8), and upper (diamonds; N = 2) sites within Bear Creek indicated Barred lines show minimum and maximum values r = 0.77; P < 0.0001

r = 0.87; P = 0.0002 A similar correlation was found for Sr:Ca ratios Scatter plot of the relationship between the Ba:Ca concentrations in water and smallmouth bass otoliths from the Buffalo River (circles; N = 8), lower (triangles; N = 13), middle (squares; N = 8), and upper (diamonds; N = 2) sites within Bear Creek. Barred lines show minimum and maximum values. r = 0.87; P = 0.0002

Element:Ca (mmol/mol) in otolith edges Sample site Ba:Ca Mg:Ca Sr:Ca Buffalo River 0.0035 A 0.030 0.71 Lower Bear 0.0038 0.028 1.03 B Middle Bear 0.0049 0.044 2.03 C Upper Bear 0.0137 0.029 1.64 Otolith element:Ca ratios differed significantly among the four sites for Ba:Ca and Sr:Ca, however, Mg:Ca ratios did not differ significantly among sites To explain the differences in variation I observed for water and otolith signatures…

Small variation among summer seasons and greater variation at core loci were found using repeated measures analysis of Ba:Ca and Sr:Ca ratios Element:Ca signatures measured at summer growth bands revealed consistent values across annuli at all sites Smallmouth bass collected in middle Bear Creek appeared to have remained or returned to reaches within middle Bear Creek in previous summers, although some may have moved into the middle reaches from lower Bear Creek Summer element:Ca signatures in lower Bear Creek and the Buffalo River remained constant across summers and suggested high site fidelity for bass collected from those areas Core element:Ca values for age 2 individuals had more variability than cores of other ages and suggested that those individuals crossed greater distances to reach the collection sites or inherited maternal signatures from parents that moved into the area to spawn

Discussion Site fidelity across consecutive summers Trace element concentrations in Bear Creek Useful trace elements Classification of fish to collection sites Ba:Ca and Sr:Ca ratios in water samples I collected within Bear Creek and the Buffalo River were temporally stable and spatially variable Chemical signatures in otoliths were directly correlated with water chemistry I classified smallmouth bass to their respective sites within Bear Creek and the Buffalo River with relatively high accuracy using otolith element:Ca values Comparison of element:Ca ratios across years revealed consistency in chemical signatures and suggested that bass in these streams exhibited site fidelity across summers Analysis of core loci suggested that smallmouth bass in these sites might have immigrated from other stream reaches

Survival Objective: examine and compare bass survival in Bear Creek and Buffalo River To determine habitat use, I measured physical characteristics at bass relocation sites Measures included stream width, water temperature, percent canopy at right and left banks, estimates of fish cover At five equally-spaced points along a transect positioned over the location of radio-marked bass I measured water depth, substrate particle size, and water velocities Data were compared among seasons and streams using ANOVA and MANOVA

Survival Kaplan-Meier known fate 5 month cutoff for unknowns Examined survival among stream-use categories and periods AICc to select model Model averaging To estimate survival rates of telemetered bass, their encounter histories were input to program MARK and the Kaplan-Meier known fate estimator was used I partitioned 17 months of tracking data into 14 separate sampling occasions; several months were pooled into sampling occasions due to infrequent tracking events during those periods. 49 of the 59 marked bass were included in analyses, those with tracking periods <1 month or unknown sex were excluded If transmitters were recovered within 5 months of surgery they were “believed to be expelled,” longer than 5 months and they were believed dead I examined variation in survival rates across stream-use categories (Bear Creek residents, Buffalo River residents, and using both streams) and three periods that varied in length from 4 to 7 months I used Akaike’s information criterion, adjusted for small sample size, to select the model; (AICc is a criterion for selecting the most parsimonious model, i.e., the model which best explains the variation in the data while using the fewest parameters) I used model averaging to account for model uncertainty and to create estimates of monthly survival for periods White and Burnham 1999

Ŝannual = (Ŝ5month)5 (Ŝ7month) 7 Annual Survival Ŝannual = (Ŝ5month)5 (Ŝ7month) 7 Delta method  var(Ŝannual ) Annual survival estimates were extrapolated using monthly estimates from the first two periods and variances were calculated using the delta method Williams et al. 2002

Survival Model k AICc wt. ΔAICc period + sex + intercept 4 0.233 0.00 0.201 0.29 group 0.151 0.87 period + total length 0.142 0.98 period + group 9 0.134 1.10 period + sex 0.071 2.40 period + length + sex 5 0.050 3.10 period + length * sex 6 0.017 5.20 Minimum AICc = 107.38 Model selection for estimating smallmouth bass survival among stream-use categories was uncertain The highest AICc weight was 0.2326 Rule of thumb: when the difference in AIC between 2 models is <2, then both models have equal weight in the data Seasonal effect on bass survival was included in seven of the eight top models from a larger set of candidate models The most plausible model had effects due to season, sex as a covariate, and common intercepts A small difference in AICc (values among the top five models suggested support for a real difference between the models did not exist

Survival Buffalo River residents had significantly lower survival rates than Bear Creek residents and bass using both streams in April–August 2003 and September 2003–March 2004 Survival rate of Bear Creek residents was significantly higher during September 2003–March 2004 than April–August 2003 and April–July 2004 No significant differences existed among periods for Buffalo River residents and bass using both streams Six of the 49 radio-marked smallmouth bass included in analysis of survival were active during the last period (September 2003–March 2004).

Survival Annual survival rates among stream-use categories were not significantly different

Discussion Survival Angler mortality Compared to other estimates Angler exploitation is probably the greatest cause of mortality for North American populations of adult smallmouth bass Disproportionate angling pressure may have resulted in my semi-annual estimates of survival being higher for “Bear Creek residents” and bass “using both streams” than “Buffalo River residents.” My estimates of annual survival were similar to another study conducted upstream in the Buffalo River that reported an annual survival rate of 64% for fish ranging from age 1 to 5 (Kilambi et al. 1977). Annual survival rates in other lotic systems have ranged from 34% for smallmouth bass ages 0 through 3 in Livingston Branch, Wisconsin (Paragamian and Coble 1975) to 39% for bass of age 2 and older in Glover Creek, Oklahoma (Orth et al. 1983).

Conclusions Consideration of tributary populations Mainstem quality reflects tributary quality Water development in tributaries Flow dynamics The condition of tributaries and the populations they sustain should be considered when attempting to understand and manage a stream and the organisms inhabiting it Other studies have found tributaries to provide important spawning, nursery, and juvenile habitat for smallmouth bass, as well as function as population reservoirs to recolonize mainstem fish communities if ever an acute decline in the population occurs (Coble 1975; Montgomery et al. 1980; Forbes 1989; Lyons and Kanehl 2002) Additionally, the quality of water and habitat in streams are directly affected by the quality of water and habitat in their tributaries It has been suggested for other systems that water development on creeks would probably provide barriers to movement, alter the annual hydrographic cycle, and modify water quality, which could lead to changes in the fish community (Smith and Hubert 1989) Alterations to the existing flow dynamics within Bear Creek may adversely affect movement strategies of smallmouth bass inhabiting reaches within the tributary and mainstem and reduce the quality and quantity of available fish habitat. Modifications such as these could ultimately reduce survival rates of smallmouth bass inhabiting these streams. Some smallmouth bass populations are using habitats in both Bear Creek and the Buffalo River flow regime allows for movement of smallmouth bass during spring and fall, and limits movement during summer drying events Altering the natural flow regime in Bear Creek may adversely affect the opportunities smallmouth bass have to migrate within the creek and the Buffalo River The presence of smaller bass (ages 0 and 1) and the absence of larger ones in shallow temporary habitat imply that movement is size dependent; suitable habitat for larger fish is located in downstream reaches that provide larger cover, deeper water, and more forage