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A global dataset of inland fisheries expert knowledge

Inland fisheries and their freshwater habitats face intensifying effects from multiple natural and anthropogenic pressures. Fish harvest and biodiversity data remain largely disparate and severely deficient in many areas, which makes assessing and managing inland fisheries difficult. Expert knowledge is increasingly used to improve and inform biological or vulnerability assessments, especially in data-poor areas. Integrating expert knowledge on the distribution, intensity, and relative influence of human activities can guide natural resource management strategies and institutional resource allocation and prioritization. This paper introduces a dataset summarizing the expert-perceived state of inland fisheries at the basin (fishery) level. An electronic survey distributed to professional networks (June-September 2020) captured expert perceptions (n = 536) of threats, successes, and adaptive capacity to fisheries across 93 hydrological basins, 79 countries, and all major freshwater habitat types. This dataset can be used to address research questions with conservation relevance, including: demographic influences on perceptions of threat, adaptive capacities for climate change, external factors driving multi-stressor interactions, and geospatial threat assessments.

Scientific Data↗

Survey of stocking policies for tailwater trout fisheries in the southern United States

A survey of the 16 southern states showed that 48 tailwaters in 13 states were stocked with trout in 1980. Of the almost 3.7 million trout released in these waters, 81% were of catchable size and 19% were fingerlings (< 150mm). Tailwaters received 32% of all trout stocked in the South; nearly 95% of the tailwater fish were rainbow trout ( Salmo gairdneri ). A trend away from "put-grow-and-take" fisheries toward "put-and-take" fisheries was noted. Limited creel data confirmed that fishing pressure in southern tailwaters was heavy, and that 25 to 90% of the trout stocked were recovered by anglers

Progressive Fish-Culturist↗

Trophic relations of introduced flathead catfish in an atlantic river

The flathead catfish Pylodictis olivaris is a large piscivore that is native to the Mississippi and Rio Grande river drainages but that has been widely introduced across the United States. River ecologists and fisheries managers are concerned about introduced flathead catfish populations because of the negative impacts on native fish communities or imperiled species associated with direct predation and indirect competition from this apex predator. We studied the trophic relations of introduced flathead catfish in an Atlantic river to further understand the effects on native fish communities. Crayfish (Astacidea) occurred most frequently in the flathead catfish diet, while sunfish Lepomis spp. comprised the greatest percentage by weight. Neither of two sympatric imperiled fish species (the federally endangered Cape Fear shiner Notropis mekistocholas and the Carolina redhorse Moxostoma sp., a federal species of concern) was found in any diet sample. An ontogenetic shift in diet was evident when flathead catfish reached about 300 mm, and length significantly explained the variation in the percent composition by weight of sunfish and darters Etheostoma and Percina spp. Flathead catfish showed positive prey selectivity for taxa that occupied similar benthic microhabitat, highlighting the importance of opportunistic feeding and prey encounter rates. Flathead catfish displayed a highly variable diel feeding chronology during July, when they had a mean stomach fullness of 0.32%, but then showed a single midday feeding peak during August (mean fullness = 0.52%). The gastric evacuation rate increased between July (0.40/h) and August (0.59/h), as did daily ration, which more than doubled between the 2 months (3.06% versus 7.37%). Our findings increase the understanding of introduced flathead catfish trophic relations and the degree of vulnerability among prey taxa, which resource managers may consider in fisheries management and conservation of native fish populations and imperiled species.

Transactions of the American Fisheries Society↗

Emerging viral diseases of fish and shrimp

The rise of aquaculture has been one of the most profound changes in global food production of the past 100 years. Driven by population growth, rising demand for seafood and a levelling of production from capture fisheries, the practice of farming aquatic animals has expanded rapidly to become a major global industry. Aquaculture is now integral to the economies of many countries. It has provided employment and been a major driver of socio-economic development in poor rural and coastal communities, particularly in Asia, and has relieved pressure on the sustainability of the natural harvest from our rivers, lakes and oceans. However, the rapid growth of aquaculture has also been the source of anthropogenic change on a massive scale. Aquatic animals have been displaced from their natural environment, cultured in high density, exposed to environmental stress, provided artificial or unnatural feeds, and a prolific global trade has developed in both live aquatic animals and their products. At the same time, over-exploitation of fisheries and anthropogenic stress on aquatic ecosystems has placed pressure on wild fish populations. Not surprisingly, the consequence has been the emergence and spread of an increasing array of new diseases. This review examines the rise and characteristics of aquaculture, the major viral pathogens of fish and shrimp and their impacts, and the particular characteristics of disease emergence in an aquatic, rather than terrestrial, context. It also considers the potential for future disease emergence in aquatic animals as aquaculture continues to expand and faces the challenges presented by climate change.

Veterinary Research↗

A scientific basis for restoring fish spawning habitat in the St. Clair and Detroit Rivers of the Laurentian Great Lakes

Loss of functional habitat in riverine systems is a global fisheries issue. Few studies, however, describe the decision-making approach taken to abate loss of fish spawning habitat. Numerous habitat restoration efforts are underway and documentation of successful restoration techniques for spawning habitat of desirable fish species in large rivers connecting the Laurentian Great Lakes are reported here. In 2003, to compensate for the loss of fish spawning habitat in the St. Clair and Detroit Rivers that connect the Great Lakes Huron and Erie, an international partnership of state, federal, and academic scientists began restoring fish spawning habitat in both of these rivers. Using an adaptive management approach, we created 1,100 m 2 of productive fish spawning habitat near Belle Isle in the Detroit River in 2004; 3,300 m 2 of fish spawning habitat near Fighting Island in the Detroit River in 2008; and 4,000 m 2 of fish spawning habitat in the Middle Channel of the St. Clair River in 2012. Here, we describe the adaptive-feedback management approach that we used to guide our decision making during all phases of spawning habitat restoration, including problem identification, team building, hypothesis development, strategy development, prioritization of physical and biological imperatives, project implementation, habitat construction, monitoring of fish use of the constructed spawning habitats, and communication of research results. Numerous scientific and economic lessons learned from 10 years of planning, building, and assessing fish use of these three fish spawning habitat restoration projects are summarized in this article.

Detroit River, St. Clair River↗

Mobile fishing gear reduces benthic megafaunal production on Georges Bank

This study addresses the effect of mobile fishing gear disturbance on benthic megafaunal production on the gravel pavement of northern Georges Bank. From 1994 to 2000, we sampled benthic megafauna with a 1 m Naturalists' dredge at shallow (47 to 62 m) and deep (80 to 90 m) sites. The cessation of fishing in large areas of Georges Bank in January 1995 allowed us to monitor changes in production at a previously disturbed site. Production at a shallow disturbed site varied little over the sampling period (32 to 57 kcal m-2 yr-1) and was markedly lower than production at the nearby recovering site, where production increased from 17 kcal m-2yr -1 in 1994 before the closure to 215 kcal m-2 yr -1 in 2000. Atlantic sea scallops Placopecten magellanicus and green sea urchins Strongylocentrotus droebachiensis dominated production at the recovering site. The community production:biomass ratio decreased over time at the recovering site as the sea scallop population matured. At the deep sites, production remained significantly higher at undisturbed sites (174 to 256 kcal m-2 yr-1) than at disturbed sites (30 to 52 kcal m -2 yr-1). The soft-bodied tube-building polychaete Thelepus cincinnatus dominated production at the undisturbed site, while hard-shelled bivalve molluscs Astarte spp. and P. magellanicus were prevalent at the disturbed site. Mobile fishing gear disturbance has a conspicuous effect on benthic megafaunal production in this hard-bottom habitat. Cessation of mobile fishing has resulted in a marked increase in benthic megafaunal production. These findings should help fishery managers to gauge the costs and benefits of management tools such as area closures and low-impact fishing gears.

Georges Banks↗

The occurrence of the colonial ascidian Didemnum sp. on Georges Bank gravel habitat: ecological observations and potential effects on groundfish and scallop fisheries

The colonial ascidian Didemnum sp. is present on the Georges Bank fishing grounds in a gravel habitat where the benthic invertebrate fauna has been monitored annually since 1994. The species was not noted before 2002 when large colonies were first observed; and by 2003 and 2004 it covered large areas of the seabed at some locations. The latest survey in 2005 documented the tunicate's presence in two gravel areas that total more than 67 nm 2 (230 km 2 ). The affected area is located on the Northern Edge of the bank in United States waters near the U.S./Canada boundary ( Fig. 1). This is the first documented offshore occurrence of a species that has colonized eastern U.S. coastal waters from New York to Maine during the past 15–20 years ( U.S. Geological Survey, 2006). Video imagery shows colonies coalescing to form large mats that cover more than 50% of the seabed along some video/photo transects. The affected area is an immobile pebble and cobble pavement that lies at water depths of 40 to 65 m where strong semidiurnal tidal currents reach speeds of 1 to 2 kt (50–100 cm/s). The water column is mixed year round, ensuring a constant supply of nutrients to the seabed. Annual temperatures range from 4 to 15 °C ( Mountain and Holzwarth, 1989). The gravel areas are bounded by sand ridges whose mobile surfaces are moved daily by the strong tidal currents. Studies commenced here in 1994 to characterize the gravel habitat and to document the effects of fishing disturbance on it ( Collie et al., 2005).

Massachusetts↗

Standardized methods for Grand Canyon fisheries research 2015

This document presents protocols and guidelines to persons sampling fishes in the Grand Canyon, to help ensure consistency in fish handling, fish tagging, and data collection among different projects and organizations. Most such research and monitoring projects are conducted under the general umbrella of the Glen Canyon Dam Adaptive Management Program and include studies by the U.S. Geological Survey (USGS), U.S. Fish and Wildlife Service (FWS), National Park Service (NPS), the Arizona Game and Fish Department (AGFD), various universities, and private contractors. This document is intended to provide guidance to fieldworkers regarding protocols that may vary from year to year depending on specific projects and objectives. We also provide herein documentation of standard methods used in the Grand Canyon that can be cited in scientific publications, as well as a summary of changes in protocols since the document was first created in 2002.

Grand Canyon↗

Effects of historical land-cover changes on flooding and sedimentation, North Fish Creek, Wisconsin

North Fish Creek, a Wisconsin tributary to Lake Superior, is an important recreational fishery that is potentially limited by the loss of aquatic habitat caused by accelerated flooding and sedimentation. A study of the historical flooding and sedimentation characteristics of North Fish Creek was done to determine how North Fish Creek responded to human-caused changes in land cover since European settlement of the region in the 1870's. Geomorphic field evidence combined with hydrologic and sediment-transport modeling indicate that historical clear-cut logging, followed by agricultural activity, significantly altered the hydrologic and geomorphic conditions of North Fish Creek. The geomorphic responses to land-cover changes were especially sensitive to the location of the reaches along the main stem and on the timing of large floods. On the basis of geomorphic evidence in flood-plain deposits and abandoned channels, the size of floods and sediment loads also increased in North Fish Creek after conversion of forested land to cropland and pasture. Changes in channel characteristics were particularly noticeable after record floods in 1941 and 1946. The upper main stem channel bed eroded downward at least 3 meters and the channel capacity at least doubled after European settlement. In the lower stem, the post-settlement sedimentation rate on the flood plain and in the channel is 4 to 6 times pre-settlement rates. The water table also appears to be rising near the mouth of North Fish Creek, perhaps consistent with (1) elevated local streambed elevations caused by sedimentation and (2) a slow relative rise in the local level of Lake Superior due to crustal rebound from glaciation. Along a transitional reach of the main stem between the upper and lower main stem, there is evidence of accelerated flood-plain sedimentation initially following European settlement. Since at least the 1940's, however, the channel bed in the transitional reach has eroded about 1 meter and the channel capacity has at least doubled. Results from hydrologic and sediment-transport modeling indicate that modern flood peaks and sediment loads in North Fish Creek may be double that expected under pre-settlement forest cover. During maximum agricultural activity in the mid-1920's to mid-1930's, flood peaks probably were about 3 times larger and sediment loads were about 5 times larger than expected under pre-settlement forest cover. These results indicate that future changes from pasture or cropland to forest will help reduce flood peaks, thereby reducing erosion and sedimentation. The addition of detention basins (to decrease flood peaks) on tributaries to North Fish Creek, or bank and instream restoration (to decrease erosion) in the upper main stem, also may help reduce the contribution of sediment from the upper main stem to the transitional section and lower main stem of the creek.

Wisconsin↗

COVID-19 pandemic impacts on global inland fisheries

The COVID-19 pandemic has led to environmental recovery in some ecosystems from a global “anthropause,” yet such evidence for natural resources with extraction or production value (e.g., fisheries) is limited. This brief report provides a data-driven global snapshot of expert-perceived impacts of COVID-19 on inland fisheries. We distributed an online survey assessing perceptions of inland fishery pressures in June and July 2020 to basin-level inland fishery experts (i.e., identified by the Food and Agriculture Organization of the United Nations across the global North and South); 437 respondents from 79 countries addressed 93 unique hydrological basins, accounting for 82.1% of global inland fish catch. Based on the responses analyzed against extrinsic fish catch and human development index data, pandemic impacts on inland fisheries 1) add gradation to the largely positive environmental narrative of the global pandemic and 2) identify that basins of higher provisioning value are perceived to experience greater fishery pressures but may have limited compensatory capacity to mitigate COVID-19 impacts along with negative pressures already present.

PNAS↗

Age, growth, sex ratio, and maturity of the whitefish in central Green Bay and adjacent waters of Lake Michigan

This study is based on 1,023 whitefish, Coregonus clupeaformis (Mitchill)--819 in seven samples from five localitites in central Green Bay in 1948-49 and 1851-52 and 204 in a single 1948 collection from northwestern Lake Michigan proper. Records of age indicated unusual strength for only one year class--1943 which strongly dominated the 1948 sample from Lake Michigan and the 1949 sample from Green Bay and was well represented in the 1948 collection from green Bay. Collection of 1951-52 without exception were dominated by age group III. Length distributions of samples varied widely according to the age composition. Among fish more than 2 years old, the length distributions of age groups overlapped broadly. Several 1-inch intervals included fish of four age groups. The length-weight relation varied considerably among central Green Bay samples, but differences among localitites were nearly equalled by the year-to-year difference at a single locality. Lake Michigan whitefish were generally lighter than those from Green Bay. Weight increased to the 3.386 power of length in Green Bay (combined samples) and the 3.359 power in Lake Michigan. Growth in length, calculated by direct proportion from diameter measurements of growth fields on scales, differed among localities in central Green Bay and between samples of different years at a single locality. If permanent locality differences exist they are not large and can be obscured by the evident annual fluctuations of growth. The grand average calculated length of Green Bay whitefish (combined collections) exceeded that of Lake Michigan fish in all years of life. The advantage was greatest (2.2 inches) at 3 years (calculated lengths of 16.0 inches and 13.8 inches) and subsequently declined to 0.5 inch at 9 years (lengths of 24.6 and 24.1 inches). Both groups reached the minimum legal length of 17 inches during the fourth growing season. Green Bay whitefish also had the larger calculated weights. The advantage reached 9.3 ounces in 3 years (calculated weights of 22.4 and 13.1 ounces). In years of life 4-9, the weight advantage over Lake Michigan fish ranged from 8.7 ounces, (seventh year; weights of 74.4 and 65.7 ounces) to 12.2 ounces (ninth year; weights of 96.2 and 84.0 ounces). Comparison of growth of whitefish at four localities in northern Lake Michigan indicates that fastest growth is in central Green Bay and slowest near the Fox Islands. Growth is intermediate and similar in northwestern Lake Michigan proper and sorthern Green Bay. Youngest mature male whitefish in green Bay belonged to age group II and youngest mature females to age group III. All IV-group fish were mature. Shortest mature males were at 14.5-14.9 inches and shortest mature females at 16.5-16.9 inches. All males longer than 17.9 inches and all females longer than 18.4 inches were mature.

Fishery Bulletin of the U.S. Fish and Wildlife Ser↗

Electrofishing and the effects of depletion sampling on fish health: A review and recommendations for additional study

Depletion sampling in combination with multiple-pass electrofishing is an important fisheries management tool for wadeable streams. This combination of techniques has been used routinely by federal and state fishery management agencies for several decades as a reliable means to obtain quantitative data on trout populations or to describe fish community structure. In this paper we review the effects of electrofishing on fish and discuss this within the context of depletion sampling and multiple exposures of fishes to electric fields. The multiple wave forms most commonly used in sampling (alternating current, direct current, and pulsed direct current) are discussed as well as electrofishing induced response, injury and physiological stress. Fish that survive electrofishing injuries are more likely to suffer short and long-term adverse effects to their behavior, health, growth, or reproduction. Of greatest concern are the native, non-target species that may be subjected to multiple electrical shocks during the course of a 3-pass depletion survey. These exposures and their effects on the non-target species warrant further study as do the overall effects of electrofishing on populations and community structure.

Conference Paper↗