Spawning Substrate Research Articles

Gravel Addition as a Habitat Restoration Technique for Tailwaters

AbstractWe assessed the efficacy of passive gravel addition at forming catostomid spawning habitat under various flow regimes in the Cheoah River, a high‐gradient tailwater river in North Carolina. The purpose was to provide a case study that included recommendations for future applications. A total of 76.3 m3 (162 tons) of washed gravel (10–50 mm) was passively dumped down the streambank and into the channel in four locations. Gravel sites differed in terms of average reach slope, bank slope, and the initial volume of gravel added, which could have influenced gravel entrainment. Maps of gravel movement under various flows suggested that large‐magnitude discharges (≥113 m3/s) caused extensive migration; however, less obvious, smaller discharges (∼28 m3/s) still caused substantial shifting, which may influence the stability of catostomid spawning substrates. Following gravel addition, the proportion of gravel in the streambed was significantly higher at all gravel sites. However, comparisons of sites to reference stream reaches suggested that sand, gravel, and cobble were still extremely deficient. Additionally, the volume of gravel was inadequate to create gravel depths that provided suitable habitat for catostomid spawning. Although periodic, passive gravel additions may take years to provide suitable spawning habitat for some fish species, we found that river chub Nocomis micropogon utilized the newly added gravel for spawning.

Variations in the fish community in lake Piediluco (Italy) caused by changes in the lake’s trophic status and the introduction of alien species

Summary The composition of fish populations in lake Piediluco has undergone significant changes in recent years, mainly as a result of environmental deterioration due to the eutrophication of its waters and the introduction of some alien species. Lake Piediluco is a natural, regulated lake, which has been used for the production of hydroelectric power since 1908. Over the years, the trophic status of the lake has been profoundly modified: until 1980 it was mesotrophic; by 1989 it had become eutrophic, and now it is deemed to be hyper-eutrophic. The aim of this research was to analyze variations in the composition of fish populations in relation to the trophic evolution of the lake and the introduction of alien species. The data on fish populations were gathered during four monitoring campaigns carried out in 1988, 1996, 1999 and 2004. To estimate the abundance of the various species, catches were standardized in terms of catch per unit effort (CPUE). The results of the research reveal that the increase of the trophic status of the lake has been accompanied by a qualitative and quantitative change in the composition and structure of the fish community, which is being increasingly dominated by omnivorous cyprinids, such as Scardinius erythrophthalmus and the alien Rutilus aula. This is taking place at the expense of species that are ecologically less resilient and commercially more interesting, supported by provincial management policies as annual repopulation programs and deployment of artificial spawning substrates. Moreover, in more recent years the presence of some new alien species has been recorded, such as Rutilus rutilus and Gymnocephalus cernuus. These species, which were not previously found, pose a further threat to commercial fishing in the lake.

Development of New Intensive Hatchery Methods for Rosy Red Fathead Minnow

AbstractFathead minnow Pimephales promelas farming practices have remained relatively unchanged for decades. To develop new intensive hatchery methods for the rosy red fathead minnow (a color variant of the fathead minnow), we evaluated spawning substrate preferences, egg mimics, anti‐fungal treatments for eggs, and fry stocking densities. Rosy red fathead minnow laid significantly more eggs on a single‐layer substrate than on a multilayered substrate but showed little preference between a firm substrate and a flexible substrate. The fish strongly preferred nesting substrates with glass‐bead egg mimics over plain (control) substrates or substrates with painted‐dot mimics. Eggs treated with chemicals (formalin or hydrogen peroxide at 500, 1,000, or 1,500 mg/L) had higher hatch rates (62.3–81.7%) than did controls (34.3%). The once‐daily hydrogen peroxide treatment was equally effective as multiple applications (2–3 applications/d) and resulted in fewer deformities. When newly hatched rosy red fathead minnow fry were stocked at densities of 49, 198, 346, 495, and 643 fry/m2 in pools for 85 d, mean fish weight decreased logarithmically with final density (R 2 = 0.953), while yield increased with initial density (R 2 = 0.846). A cost analysis for fry production levels of 10, 30, 50, and 70 million fry found that the most costly stage was egg collection followed by fry holding, egg incubation, and egg removal. Estimated costs to produce 1 million fry decreased from US$514 to $356 with increasing fry production, indicating economies of scale. Use of spawning substrates with glass‐bead egg mimics has the potential to decrease these costs by increasing egg collection efficiency.

Golden Shiner Egg Production during a Spawning Season

AbstractThis study determined the number of eggs produced daily by golden shiners Notemigonus crysoleucas during a 111‐d spawning season and the relationship of egg production to water temperature. On March 15, 2000, four 5.9‐m2, plastic‐lined pools were each stocked with fifty 1‐year‐old golden shiners. Mean (±SD) individual weight of fish at stocking was 9.2 ± 3.7 g. During March 16 through July 4, the spawning substrate in each pool was collected daily and replaced with clean substrate. Eggs were removed from mats in a 1.5% sodium sulfite bath, and the total volume of eggs from each pool was recorded. The mean number of eggs per unit volume (based on twenty‐seven 2‐mL samples) was 704 ± 109 eggs/mL. Approximately 2.75 million eggs were produced by no more than 200 brooders (∼2.4‐kg total mass) over 111 d. Egg production was greatest during the month of May (average = 14,339 eggs·kg−1·d−1). The number of eggs collected daily showed a significant positive correlation with water temperature (P < 0.05) up to 22°C and then declined with further increases in water temperature.

Channel Morphology Response to Selective Wood Removals in a Sand‐Laden Wisconsin Trout Stream

AbstractLarge sand bed loads in trout stream headwaters can limit salmonid spawning habitat and reproductive success. This phenomenon has been observed in many northern Wisconsin watersheds, where historic logging practices are the likely source of the sediment loading. Presently, sediment transport is limited by abundant woody debris, causing channels to aggrade and bury gravels. We evaluated the impacts of a wood debris and beaver dam removal remediation strategy on fine sediment transport and exposure of the underlying gravel and cobble substrates in a second‐order Lake Superior tributary. A 300‐m treatment reach received selective wood removals and was compared with both an upstream 300‐m reference reach receiving no alteration and a downstream reach to monitor the effects of transferred fine sediment. Physical channel measurements were taken before the wood removal process, with repeat sampling at 10 and 12 months posttreatment. The wood removal treatment resulted in a significant 25% narrowing of mean stream widths, a 32% increase in mean flow velocities, a 58% reduction in the sand bed load, and a 400% increase in the available coarse substrate across the channel. Grain size distributions coarsened noticeably from pre‐ to posttreatment. Water depth and temperature were not altered by the treatment, and the reference station physical measures were relatively unchanged over the 12‐month study period. Immediately after the wood removal there was an observable pulse of sediment traveling through the downstream reach that increased the sand bed load, increased stream widths, and filled pools. However, these impacts diminished with time, and near‐preremoval conditions had returned after 12 months. The wood removal treatment caused a significant reduction in sand content and enhanced the availability of salmonid spawning substrates.

Patch-specific spawning is linked to restoration of a sediment-disturbed lowland river, south-eastern Australia

Landscape-scale, terrestrial modifications of catchments can increase river sediment loads. In some rivers, the development of ‘sand-slugs’ (i.e. discrete slugs of travelling sand particles) subsequently alters habitat structure with links to declines in regional fish diversity. Increasingly, river channel restoration is being used to conserve biodiversity in sediment-disturbed rivers, but there are few examples to guide restoration efforts. In particular, few studies examine the effect of restoration on ecological processes such as spawning. We report on a trial restoration procedure, consisting of sediment extraction and woody debris replacement undertaken in two 1500 m reaches of the Glenelg River, south-eastern Australia. We aimed to examine the association between reach-scale restoration and fish spawning, predicting that reconstructed channel types (pools and runs) would be used more frequently than corresponding un-modified channel types for spawning. Artificial (polyvinylchloride (PVC) tubes) and natural (small woody debris) spawning substrates were used to examine the association of fish spawning with reach and channel type. Restoration increased wood volume, but only increased average run depth at one reach. Species including Gadopsis marmoratus, Philypnodon grandiceps, Hypseleotris spp., Nannoperca variegata and Cherax destructor were observed within spawning substrates, but only P. grandiceps frequently spawned on PVC tubes and sparsely on small woody debris substrates. Spawning frequency varied between reach and channel types, with pools in both restored and un-manipulated reaches used more frequently than runs. Restored pools were less frequently used than un-manipulated pools, but restored runs were used up to 6 times more frequently than un-manipulated runs, indicating that restoration of the shallowest parts of the channel increased spawning opportunities for P. grandiceps. This type of channel restoration may facilitate ecological processes that underpin the persistence of riverine fish populations.

Kootenai River velocities, depth, and white sturgeon spawning site selection – a mystery unraveled?

The Kootenai River white sturgeon Acipenser transmontanus population in Idaho, US and British Columbia (BC), Canada became recruitment limited shortly after Libby Dam became fully operational on the Kootenai River, Montana, USA in 1974. In the USA the species was listed under the Endangered Species Act in September of 1994. Kootenai River white sturgeon spawn within an 18-km reach in Idaho, river kilometer (rkm) 228.0–246.0. Each autumn and spring Kootenai River white sturgeon follow a ‘short two-step’ migration from the lower river and Kootenay Lake, BC, to staging reaches downstream of Bonners Ferry, Idaho. Initially, augmented spring flows for white sturgeon spawning were thought to be sufficient to recover the population. Spring discharge mitigation enhanced white sturgeon spawning but a series of research investigations determined that the white sturgeon were spawning over unsuitable incubation and rearing habitat (sand) and that survival of eggs and larvae was negligible. It was not known whether post-Libby Dam management had changed the habitat or if the white sturgeon were not returning to more suitable spawning substrates farther upstream. Fisheries and hydrology researchers made a team effort to determine if the spawning habitat had been changed by Libby Dam operations. Researchers modeled and compared velocities, sediment transport, and bathymetry with post-Libby Dam white sturgeon egg collection locations. Substrate coring studies confirmed cobbles and gravel substrates in most of the spawning locations but that they were buried under a meter or more of post-Libby Dam sediment. Analysis suggested that Kootenai River white sturgeon spawn in areas of highest available velocity and depths over a range of flows. Regardless of the discharge, the locations of accelerating velocities and maximum depth do not change and spawning locations remain consistent. Kootenai River white sturgeon are likely spawning in the same locations as pre-dam, but post-Libby Dam water management has reduced velocities and shear stress, thus sediment is now covering the cobbles and gravels. Although higher discharges will likely provide more suitable spawning and rearing conditions, this would be socially and politically unacceptable because it would bring the river elevation to or in excess of 537.66 m, which is flood stage. Thus, support should be given to habitat modifications incorporated into a management plan to restore suitable habitat and ensure better survival of eggs and larvae.

Influence of European sculpin, Cottus gobio, on Atlantic salmon Salmo salar, recruitment and the effect of gravel size on egg predation – implications for spawning habitat restoration

Abstract The study examined if recruitment of juvenile Atlantic salmon, Salmo salar L., was influenced by the presence of European sculpin, Cottus gobio L., and if the spawning substrate size used by salmon influences sculpin predation on salmon eggs. A combination of information on spawning site selection by female salmon and associated densities of juvenile salmon indicated that recruitment of juvenile salmon was 10 times lower in areas where sculpin was present than areas without sculpin. Predation rate on salmon eggs was found to be dependent on substrate size in artificial redds created in stream aquaria using four different sizes of substrate (13, 23, 37 and 62 mm). Predation rate averaged 83% in the aquaria with the largest substrate size, whereas a rate of only 2–3% was observed using smaller substrate sizes. Sculpin may thus be an important factor influencing the recruitment of juvenile salmon. Selecting small enough gravel sizes during restoration of salmon spawning habitat could therefore be important to minimise egg predation.

Distribution of egg strands of perch (Perca fluviatilis L.) with respect to depth and spawning substrate

The distribution of egg strands of perch Perca fluviatilis was studied in relation to water depth and spawning substrate during late April and early May 2007 in Chabařovice Lake, Czech Republic, using SCUBA divers and parallel transects. The depth distribution of egg strands differed significantly between the two sampling dates, being much deeper in early May compared to late April. Perch used at least seven different spawning substrates of which the most important were curly pondweed Potamogeton crispus, worm weed Artemisia sp. and common reed Phragmites communis. However, while living submerged vegetation, although more abundant, was generally avoided, dead submerged vegetation was strongly preferred. It appears that dead vegetation is an ideal spawning substrate for perch since placement of the egg strands over those hard, complex three-dimensional structures ensures that the eggs remain well oxygenated 24 hours a day. Factors with significant influence on the distribution of egg strands were as follows (in order of decreasing influence): depth of deposition, type of spawning substrate, date of spawning and temperature at the depth of deposition.

17α‐Ethinylestradiol alters reproductive behaviors, circulating hormones, and sexual morphology in male fathead minnows (Pimephales promelas)

Ecologically relevant indicators of endocrine disruption in fish must be linked with measures of reproductive success. The ability of male fathead minnows (Pimephales promelas) to compete for, maintain, and defend a spawning substrate is paramount to reproductive success. The present study quantified alterations in male fathead minnow reproductive behaviors after exposure to environmentally relevant concentrations (0, 10, 20, or 40 ng/L) of 17alpha-ethinylestradiol (EE2) for 21 d. A video-based behavioral quantification system examined changes in male-male competitive behaviors (chasing and head-butting) and ability of males to maintain spawning substrates (nibbling and scrubbing). Behaviors analyzed included time under the spawning substrate, frequency of substrate cleaning, and conspecific aggression. Plasma hormone levels (11-ketotestosterone [11-KT], testosterone, and estradiol [E2]), vitellogenin (VTG), secondary male characteristics (tubercle count and dorsal nape pad rank), gonadosomatic index (GSI), and gonad histology also were evaluated. Exposure to 40 ng/L of EE2 decreased the ability of exposed males to compete with control males for spawning substrates (p = 0.09). Furthermore, exposed males displayed reduced frequency of substrate cleaning activities as well as chasing male competitors (p < or = 0.05). 11-Ketotestosterone, testosterone, and E2 were lower, and VTG was notably higher, in EE2-exposed males compared with control males (p < or = 0.03). 17alpha-Ethinylestradiol exposure in males also was associated with reductions in tubercles; lower GSI, gonadal maturity ranks, and number of resorbed tubercles; and presence of an ovipositor (p < or = 0.001). These data reveal alterations in male reproductive behavior that coincide with decreased hormone levels and secondary sex characteristics. Behavioral endpoints to discern potential ecological consequences in fish exposed to low concentrations of endocrine-disrupting chemicals may provide sensitive and functional indices of effect.

Broodstock management and hormonal manipulations of fish reproduction

Control of reproductive function in captivity is essential for the sustainability of commercial aquaculture production, and in many fishes it can be achieved by manipulating photoperiod, water temperature or spawning substrate. The fish reproductive cycle is separated in the growth (gametogenesis) and maturation phase (oocyte maturation and spermiation), both controlled by the reproductive hormones of the brain, pituitary and gonad. Although the growth phase of reproductive development is concluded in captivity in most fishes—the major exemption being the freshwater eel ( Anguilla spp.), oocyte maturation (OM) and ovulation in females, and spermiation in males may require exogenous hormonal therapies. In some fishes, these hormonal manipulations are used only as a management tool to enhance the efficiency of egg production and facilitate hatchery operations, but in others exogenous hormones are the only way to produce fertilized eggs reliably. Hormonal manipulations of reproductive function in cultured fishes have focused on the use of either exogenous luteinizing hormone (LH) preparations that act directly at the level of the gonad, or synthetic agonists of gonadotropin-releasing hormone (GnRHa) that act at the level of the pituitary to induce release of the endogenous LH stores, which, in turn act at the level of the gonad to induce steroidogenesis and the process of OM and spermiation. After hormonal induction of maturation, broodstock should spawn spontaneously in their rearing enclosures, however, the natural breeding behavior followed by spontaneous spawning may be lost in aquaculture conditions. Therefore, for many species it is also necessary to employ artificial gamete collection and fertilization. Finally, a common question in regards to hormonal therapies is their effect on gamete quality, compared to naturally maturing or spawning broodfish. The main factors that may have significant consequences on gamete quality—mainly on eggs—and should be considered when choosing a spawning induction procedure include (a) the developmental stage of the gonads at the time the hormonal therapy is applied, (b) the type of hormonal therapy, (c) the possible stress induced by the manipulation necessary for the hormone administration and (d) in the case of artificial insemination, the latency period between hormonal stimulation and stripping for in vitro fertilization.

Reproductive Ecology and Spawning Substrate Preference of the Northern Leatherside Chub

AbstractConservation of rare fishes is often hindered by a lack of understanding of their basic life history characteristics. We used captive‐breeding studies to determine the preferred spawning habitat and early life history characteristics of the northern leatherside chub Lepidomeda copei, a small cyprinid native to the upper Snake River basin and the Bear River drainage in the Bonneville Basin (Idaho, Utah, and Wyoming). In the first study, wild adult northern leatherside chub were given a choice of four habitats (two shallow riffle habitats and two deeper pool habitats), each with four spawning substrates (large cobble, small cobble, pebble, and a coarse artificial spawning mat) in a large rectangular tank. In the second study, adults were given a choice of three locations with different water velocities (9.5, 12.9, or 19.0 cm/s) but the same substrate size (small cobble). Successful spawning occurred in both studies. Northern leatherside chub spawned almost exclusively over the small cobble substrate (99.6% of total young). Habitat selection was significant, but the patterns were not consistent across tanks; uncovered pool habitat was selected in two tanks and the upper riffle habitat was primarily selected in the third tank. In addition, northern leatherside chub preferentially chose the site with the highest flow (19 cm/s) for spawning. Early life history characteristics (embryo size, time to hatch, larvae size, eggs per spawn, time to swim‐up, and fry growth) were estimated from the reproductive output of the spawning studies. Small cobble is needed for northern leatherside chub reproduction, and its availability may be among the limiting factors for northern leatherside chub populations.

The use of artificial spawning substrates as media to support the reproduction of Eurasian perch in Lake Piediluco

Lake Piediluco is a naturally regulated lake used for hydroelectric purposes. Management of the lake and the eutrophic conditions of its waters have had a negative impact on fish populations, particularly that of Eurasian perch (Perca fluviatilis L.). In order to increase the natural reproduction of this species, an experimental program was undertaken from 1997 to 2003 to facilitate reproduction by providing artificial spawning substrates. In Lake Piediluco perch spawn from March to May. Egg ribbons ranged in length from 30 to 180 cm and contained from 12,740 to 205,466 eggs. The fraction of degenerated eggs ranged from 0.20% to 63.30% (average 10.20%). The results demonstrate the effectiveness of artificial substrates as suitable substrates for the reproduction of perch.

FORECASTING RELATIVE IMPACTS OF LAND USE ON ANADROMOUS FISH HABITAT TO GUIDE CONSERVATION PLANNING

Land use change can adversely affect water quality and freshwater ecosystems, yet our ability to predict how systems will respond to different land uses, particularly rural-residential development, is limited by data availability and our understanding of biophysical thresholds. In this study, we use spatially explicit parcel-level data to examine the influence of land use (including urban, rural-residential, and vineyard) on salmon spawning substrate quality in tributaries of the Russian River in California. We develop a land use change model to forecast the probability of losses in high-quality spawning habitat and recommend priority areas for incentive-based land conservation efforts. Ordinal logistic regression results indicate that all three land use types were negatively associated with spawning substrate quality, with urban development having the largest marginal impact. For two reasons, however, forecasted rural-residential and vineyard development have much larger influences on decreasing spawning substrate quality relative to urban development. First, the land use change model estimates 10 times greater land use conversion to both rural-residential and vineyard compared to urban. Second, forecasted urban development is concentrated in the most developed watersheds, which already have poor spawning substrate quality, such that the marginal response to future urban development is less significant. To meet the goals of protecting salmonid spawning habitat and optimizing investments in salmon recovery, we suggest investing in watersheds where future rural-residential development and vineyards threaten high-quality fish habitat, rather than the most developed watersheds, where land values are higher.

Early Development of the Sacramento Perch

AbstractPopulations of the Sacramento perch Archoplites interruptus, California's only native centrarchid, are declining and early development of this imperiled species is poorly known. Therefore, the main objective of this study was to describe the early development of Sacramento perch from fertilization to initiation of exogenous feeding. Embryos were obtained in the laboratory by spawning induction via photoperiod‐temperature control or gonadotropin‐releasing hormone analog treatment. Gross morphology and histological analyses were integrated to describe the early development. Cleavage was synchronous until the 64‐cell stage, which allowed us to calculate the duration of one mitotic cycle during early synchronous cleavage (τ0) as 10–16 min at 25.4–25.6°C. A description of histological events from time to morulation, gastrulation, hatch, and exogenous feeding larvae is provided. Yolk sac larvae tended to adhere to the spawning substrate or sediment during the critical organogenesis stages. Larvae swam up and began exogenous feeding within 4 d postfertilization. Primordial germ cells were observed in 10‐d‐old larvae, but sex differentiation occurred after 43 d. External sexual dimorphism was not observed in early life stages.

Female goldfish signal spawning readiness by altering when and where they release a urinary pheromone

Although it is established that many species of fish release hormonally derived sex pheromones in their urine, whether these cues are unspecialized metabolic by-products or specialized communicatory signals is not known. Here, we addressed this question in the goldfish, Carassius auratus (a leading model of hormonal sex pheromone function) by conducting two experiments. We first monitored urine release by sexually receptive females that were placed with a sexually active male, an inactive male, another female, or no other fish. Sexual receptivity was induced using prostaglandin F2α, a hormone also known to evoke release of 15-keto prostaglandin F2α (15K-PGF2α), a potent urinary pheromone. We found that sexually receptive females increased the frequency with which they urinated when placed with males (regardless of male sexual activity) but not females. Furthermore, females showed a strong tendency to urinate when rising into spawning substrate, suggesting they might be using urine as an attractive lure. This hypothesis was confirmed by a second experiment, which found that 15K-PGF2α attracted males to specific locations. We conclude that goldfish, and likely many other fish, control the release of urinary prostaglandin pheromones to advertise their condition and location, perhaps exemplifying an early step in the evolution of a chemical communication system.

Failure of Walleye Recruitment in a Lake with Little Suitable Spawning Habitat Is Probably Exacerbated by Restricted Home Ranges

ABSTRACT Over eight million walleye (Sander vitreus) fry are stocked annually in Honeoye Lake, a small lake in the Finger Lakes region of west-central New York. The objectives of our study were to find and describe the spawning locations and habitats of walleye and to assess natural production of fry. Twenty-three adult walleye were radio-tagged and tracked for up to 2.5 years. They established relatively small home ranges (24–188 ha) and moved more during the three-week spawning season (149 m/d) than the rest of the year (37 m/d). No naturally produced walleye eggs were collected in the Honeoye Lake inlet channel where adults congregated during the 2002 and 2003 spawning seasons, nor were fry collected in the lake until after 8.7 million were stocked in 2003. Radio-tagged walleye exhibited homing and site fidelity in Honeoye Lake but not to the few known areas with suitable spawning substrates (no eggs were collected at these locations).

Long‐Term Monitoring and Evaluation of the Lower Red River Meadow Restoration Project, Idaho, U.S.A.

Abstract Although public and financial support for stream restoration projects is increasing, long‐term monitoring and reporting of project successes and failures are limited. We present the initial results of a long‐term monitoring program for the Lower Red River Meadow Restoration Project in north‐central Idaho, U.S.A. We evaluate a natural channel design’s effectiveness in shifting a degraded stream ecosystem onto a path of ecological recovery. Field monitoring and hydrodynamic modeling are used to quantify post‐restoration changes in 17 physical and biological performance indicators. Statistical and ecological significance are evaluated within a framework of clear objectives, expected responses (ecological hypotheses), and performance criteria (reference conditions) to assess post‐restoration changes away from pre‐restoration conditions. Compared to pre‐restoration conditions, we observed ecosystem improvements in channel sinuosity, slope, depth, and water surface elevation; quantity, quality, and diversity of in‐stream habitat and spawning substrate; and bird population numbers and diversity. Modeling documented the potential for enhanced river–floodplain connectivity. Failure to detect either statistically or ecologically significant change in groundwater depth, stream temperature, native riparian cover, and salmonid density is due to a combination of small sample sizes, high interannual variability, external influences, and the early stages of recovery. Unexpected decreases in native riparian cover led to implementation of adaptive management strategies. Challenges included those common to most project‐level monitoring—isolating restoration effects in complex ecosystems, securing long‐term funding, and implementing scientifically rigorous experimental designs. Continued monitoring and adaptive management that support the establishment of mature and dense riparian shrub communities are crucial to overall success of the project.

Potential Strategies for Recovery of Lake Whitefish and Lake Herring Stocks in Eastern Lake Erie

Lake Erie sustained large populations of ciscoes ( Salmonidae: Coregoninae) 120 years ago. By the end of the 19 th century, abundance of lake whitefish ( Coregonus clupeaformis) had declined drastically. By 1925, the lake herring (a cisco) population ( Coregonus artedii) had collapsed, although a limited lake herring fishery persisted in the eastern basin until the 1950s. In the latter part of the 20 th century, the composition of the fish community changed as oligotrophication proceeded. Since 1984, a limited recovery of lake whitefish has occurred, however no recovery was evident for lake herring. Current ecological conditions in Lake Erie probably will not inhibit recovery of the coregonine species. Recovery of walleye ( Sander vitreus) and efforts to rehabilitate the native lake trout ( Salvelinus namaycush) in Lake Erie will probably assist recovery because these piscivores reduce populations of alewife ( Alosa psuedoharengus) and rainbow smelt ( Osmerus mordax), which inhibit reproductive success of coregonines. Although there are considerable spawning substrates available to coregonine species in eastern Lake Erie, eggs and fry would probably be displaced by storm surge from most shoals. Site selection for stocking or seeding of eggs should consider the reproductive life cycle of the stocked fish and suitable protection from storm events. Two potential sites in the eastern basin have been identified. Recommended management rocedures, including commercial fisheries, are suggested to assist in recovery. Stocking in the eastern basin of Lake Erie is recommended for both species, as conditions are adequate and the native spawning population in the eastern basin is low. For lake herring, consideration should be given to match ecophenotypes as much as possible. Egg seeding is recommended. Egg seeding of lake whitefish should be considered initially, with fingerling or yearling stocking suggested if unsuccessful. Spawning stocks of whitefish in the western basin of Lake Erie could be utilized.

Timing and site selection of spawning in a landlocked population of rainbow smelt in Wisconsin

To study the site selection and timing of spawning by rainbow smelt, Osmerus modax, in a freshwater system, smelt were sampled with fyke nets during the spawning run in spring 2002 and 2003. The sex ratio of smelt favored males in the early and late segments of the run, with over 90% of smelt caught being male. At the peak in the catch, females comprised 57% of the smelt collected. The gonadosomatic index of males and females declined significantly on the day of peak catch, signaling the peak in spawning activity. Higher catches of smelt occurred on cobble-dominated substrates during the peak of the run, but no site selection was apparent earlier or later. Groundwater outflow did not appear to affect catches. Our study suggests that smelt come inshore but do not select specific spawning substrates prior to or after the peak in spawning. Smelt do select cobble sites during the highest rates of spawning. The relation between the peak in spawning and site selection could have application in planning removal strategies for the species.