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USGS2026

Integrating data on a mixed stock anadromous fishery to estimate stock-specific escapement and mortalities

Objective Anadromous fisheries can affect stocks with differing management objectives. Understanding the effects of fisheries on individual stocks by quantifying final dispositions, including escapement and mortalities, is important for sustainable fishery management. Our objectives were to extend an existing management model that is used to evaluate final stock dispositions to estimate confidence intervals and to generalize the model so that it could be applied in other systems. Methods An annual run reconstruction model for estimating final dispositions of Snake River steelhead Oncorhynchus mykiss was previously developed to evaluate mortalities and escapement for each stock. We extended and generalized this model in two ways: (1) to propagate uncertainty using Monte Carlo simulation and (2) to fit the model using maximum likelihood methods. We generated confidence intervals and conducted sensitivity analyses to evaluate sources of uncertainty. Results The Monte Carlo version of the model explicitly propagates uncertainty in inputs through to model predictions, whereas the maximum likelihood version includes additional data sources, such as catch composition and escapement. We estimated disposition metrics for Snake River steelhead using the original formulation, Monte Carlo version, and the maximum likelihood version for the 2018–2019 season, and we found that the results were similar but that the maximum likelihood version provided a better fit to the observed data. Conclusions We demonstrate how to account for uncertainty when synthesizing several kinds of monitoring data. Improved characterizations of uncertainty facilitate better decision making about future data collection and fisheries management.

North American Journal of Fisheries Management↗

USGS2017

Defining a Safe Operating Space for inland recreational fisheries

The Safe Operating Space (SOS) of a recreational fishery is the multidimensional region defined by levels of harvest, angler effort, habitat, predation and other factors in which the fishery is sustainable into the future. SOS boundaries exhibit trade-offs such that decreases in harvest can compensate to some degree for losses of habitat, increases in predation and increasing value of fishing time to anglers. Conversely, high levels of harvest can be sustained if habitat is intact, predation is low, and value of fishing effort is moderate. The SOS approach recognizes limits in several dimensions: at overly high levels of harvest, habitat loss, predation, or value of fishing effort, the stock falls to a low equilibrium biomass. Recreational fisheries managers can influence harvest and perhaps predation, but they must cope with trends that are beyond their control such as changes in climate, loss of aquatic habitat or social factors that affect the value of fishing effort for anglers. The SOS illustrates opportunities to manage harvest or predation to maintain quality fisheries in the presence of trends in climate, social preferences or other factors that are not manageable.

Fish and Fisheries↗

USGS2022

Ecological and social strategies for managing fisheries using the Resist-Accept-Direct (RAD) framework

Fisheries management is a complex task made even more challenging by rapid and unprecedented socioecological transformations associated with climate change. The Resist-Accept-Direct (RAD) framework can be a useful tool to support fisheries management in facing the high uncertainty and variability associated with aquatic ecosystem transformations. Here, RAD strategies are presented to address ecological goals for aquatic ecosystems and social goals for fisheries. These strategies are mapped on a controllability matrix which explores the ability to guide a system's behaviour towards a desired state based on ecological responsiveness and societal receptivity to change. Understanding and improving the controllability of aquatic systems and fisheries can help managers to maintain the broadest suite of available RAD management strategies.

Fisheries Management and Ecology↗

USGS2018

Acoustic telemetry as a potential tool for mixed-stock analysis of fishery harvest: A feasibility study using Lake Erie walleye

Understanding stock composition is critical for sustainable management of mixed-stock fisheries. When natural markers routinely used for stock discrimination fail, alternative techniques are required. We investigated the feasibility of using acoustic telemetry to estimate spawning population contributions to a mixed-stock fishery using Lake Erie’s summer walleye (Sander vitreus) recreational fishery as a case study. Postrelease survival was estimated after tagging and used to inform simulations to evaluate how contribution estimates could be affected by survival, sample size, and expected population contributions. Walleye experienced low short-term survival after tagging, but showed higher survival after 100 days, likely allowing fish to return to spawning areas the following spring. Based on simulations, accuracy and precision of population composition increased with an increase in the number of tagged fish released, and both appeared to stabilize when ≥200 tagged fish were released. Results supported the feasibility of using acoustic telemetry to estimate spawning population contributions to mixed-stock fisheries in Lake Erie.

Michigan, Ohio↗

USGS2021

Big runs of little fish: First estimates of run size and exploitation in an amphidromous postlarvae fishery

Amphidromous postlarvae fisheries (APFs) constitute a globally widespread and distinctive class of fishery that is largely unknown to fisheries science. APFs harvest ocean-to-river migrating fishes at smaller sizes and younger ages than any other class of fishery. No quantitative estimates of run size and exploitation exist, which are needed to evaluate APF sustainability. Migrating amphidromous fishes are vectors of marine nutrients to estuaries and rivers, and run size quantification is needed to reveal the magnitude of this ecosystem function. We present a novel adaptation of trapezoidal area under the curve methods, which we apply in a Caribbean case study to yield the first simultaneous estimates of an APF run size and harvest. Run size estimates ranged 7.3–9.4 million postlarvae (926–1184 kg), and exploitation estimates (5.8%–7.0%) indicated low harvest in the Río Grande de Arecibo, Puerto Rico. Our representative run size estimates reveal that amphidromous postlarvae transport hundreds of kilograms of biomass per month to an estuary and river, the first empirical evidence that amphidromous migrations are large-magnitude material subsidies of lotic ecosystems.

Puerto Rico, Río Grande de Arecibo River↗

USGS2021

Consequences of changing water clarity on the fish and fisheries of the Laurentian Great Lakes

Human-driven environmental change underlies recent changes in water clarity in many of the world’s great lakes, yet our understanding of the consequences of these changes on the fish and fisheries they support remains incomplete. Herein, we offer a framework to organize current knowledge, guide future research, and help fisheries managers understand how water clarity can affect their valued populations. Emphasizing Laurentian Great Lakes findings where possible, we describe how changing water clarity can directly affect fish populations and communities by altering exposure to ultraviolet radiation, foraging success, predation risk, reproductive behavior, or territoriality. We also discuss how changing water clarity can affect fisheries harvest and assessment through effects on fisher behavior and sampling efficiency (i.e., catchability). Finally, we discuss whether changing water clarity can affect understudied aspects of fishery performance, including economic and community benefits. We conclude by identifying generalized predictions and discuss their implications for priority research questions for the Laurentian Great Lakes. Even though the motivation for this work was regional, the breadth of the review and generality of the framework are readily transferable to other freshwater and marine habitats.

Great Lakes↗

USGS1949

Trends in the lake trout fishery of Lake Huron through 1946

The production of lake trout, Cristivomer namaycush (Walbaum), in the United States waters of Lake Huron was highest in the earliest years for which there are statistical records, averaging 2,362,000 pounds in 1879–1894. The general level of yield was much lower but relatively stable in 1895–1939, during which period the catch averaged 1,685,000 pounds. The most recent years have seen a rapid and calamitous decline in the output; setting a new record low each year, the take decreased from 940,000 pounds in 1940 to only 38,000 pounds in 1946. The production of lake trout in the Canadian waters of Lake Huron was generally low from 1867 up to about 1883, apparently because the fishery was then in the process of development. After 1882 the yield was relatively high for 26 years and then fell away progressively as the following averages of production in pounds for different periods show: (1883–1908) Huron proper–1,749,000, Georgian Bay (including the North Channel)–2,475,000, Canadian total–4,224,000; (1909–1922) Canadian total (no data for regions within the lake)–3,753,000; (1923–1939) Huron proper–1,600,000, Georgian Bay–1,996,000, Canadian total–3,596,000. During more recent years the catch fell from 1,038,000 pounds in 1940 to 29,000 pounds in 1946 in Huron proper, from 1,688,000 to 702,000 pounds in Georgian Bay, and from 2,726,000 to 731,000 pounds in all Canadian waters. The tremendous decreases in production that have occurred in all parts of Lake Huron in recent years are generally believed to have been caused by a reduction in the abundance of lake trout resulting from attacks by the sea lamprey, which has become established and has multiplied rapidly in the upper Great Lakes. Data are available on the production of lake trout in six local regions or statistical districts of the United States waters of Lake Huron (boundaries shown in Fig. 1) in 1891–1908 and on production, fishing intensity, and the abundance of fish on the grounds in 1929–1946. The order of the districts with respect to their percentage contribution to the average annual production was the same in 1891–1908 and 1929–1943. Certain changes occurred, nevertheless, in all percentages. The northern districts (H-1, H-2) which contributed 70.3 percent of the take in 1891–1908 accounted for only 56.2 percent in 1929–1943 whereas the central (H-3, H-4) and southern (H-5, H-6) districts which yielded 18.7 and 11.0 percent, respectively, in the former period contributed 25.5 and 18.3 percent in the latter. The six districts were similar in 1929–1946 in that in all of them (1) most of the years of highest output and of most intensive fishing occurred in the early to middle 1930′s and (2) the earlier high levels were followed by declines that ultimately reduced production and fishing intensity to insignificance. The same (earlier high values followed by a decline) held for the abundance of lake trout in the northerly five districts, but the trends of fluctuation in the abundance in H-6 were opposite those in other areas. On the whole, the abundance of lake trout appeared to have little effect on fishing intensity for the species. Only in H-1 did the two exhibit significant positive correlation whereas in H-6 they showed highly significant negative correlation. Most of the factors that may counteract the expected influence of abundance on fishing intensity (economic conditions, weather, …) cannot be evaluated accurately. It was determined, however, that the collapse of the whitefish fishery in the middle and late 1930′s most probably exerted a significant depressing effect on the intensity of the gill-net fishery for lake trout in those districts (H-1, H-4, H-6) in which the two species are ordinarily captured together. The estimated abundance of lake trout in the United States waters of Lake Huron (all districts combined) had reached an extremely low level in 1946 (24 percent of the 1929–1943 average), and the complete collapse of the fishery in late years is a matter of record. The rate of decline in abundance, however, was much less rapid than the spectacular decreases in production might suggest. Although each year beginning with 1940 saw a new record low yield, the abundance was still 87 percent of average in 1942 and did not drop below 70 percent until 1944. This seeming paradox is explained by the fact that relative to average conditions, fishing intensity in 1941–1946 was lower and was decreasing much more rapidly than was abundance. PDF

Transactions of the American Fisheries Society↗

USGS1951

Status of the lake trout fishery in Lake Superior

The production of lake trout in the United States waters of Lake Superior was low (only 1,465,000 pounds) in 1879, the first year for which there is a record. Expansion of the fishery must have started soon thereafter, for the take was 3,488,000 pounds in 1885, the next year for which we have statistics, and averaged 3,416,000 pounds in 1885–1892. The years after 1892 can be divided readily into three general periods with average yields as follows: 1893–1907–4,599,000 pounds; 1908–1925–2,168,000 pounds; 1926–1949–3,049,000 pounds. A take of 3 million pounds can be held as “normal” in the modern fishery. During the three periods just listed the percentage contributions of the individual states to the United States total (as computed from the averages for individual periods) ranged from 65.1 to 71.5 for Michigan, 17.5 to 25.6 for Wisconsin, and from 9.3 to 11.0 for Minnesota. In the Canadian (Province of Ontario) waters of Lake Superior the average annual output of lake trout rose from 309,000 pounds in 1871–1882 to 900,000 pounds in 1883–1893, 1,567,000 pounds in 1894–1903, and 2,189,000 pounds in 1904–1918. This last period of relatively high yield was followed by two intervals of successively lower average catches–1,691,000 pounds in 1919–1929 and 1,395,000 pounds in 1930–1949. For the combined United States and Canadian waters of Lake Superior the general trends in the production of lake trout can be described by the following averages: 1879–1,653,000 pounds: 1885–1892–4,325,000 pounds; 1893–1907–6,236,000 pounds; 1908–1949–4,403,000 pounds. The short‐term fluctuations of production during the more recent years give evidence of periodicity in the output of lake trout in Michigan, Ontario, and in the entire lake. Furthermore, these periodic fluctuations tended to be similar in Michigan and Ontario waters. The coefficient of correlation (r) between production in Michigan and Ontario in 1920–1949 (after elimination of trend in the statistics for both areas) had the significant value of 0.456. This correlation suggests that Michigan and Ontario fishermen exploit a common stock or stocks subject to similar fluctuations. Statistics on the production of lake trout in 5 of the 6 statistical districts of the State of Michigan waters of Lake Superior (see Fig. 2 for boundaries of the districts) in 1885 suggest that in most areas the fishery was then in the process of development. Even in 1891–1908 when the general level of production was high, there is evidence that during certain periods the catch in some areas was influenced strongly by factors (such as accessibility to market) other than the natural productivity of the waters. Comparisons of the average annual output of lake trout in the individual districts in 1891–1908 and 1929–1943 (the base period for our modern statistical analysis) reveal an enormous decrease in the Whitefish Bay region (S‐6) from 916,000 pounds in 1891–1908 to only 177,000 pounds in 1929–1943, a substantial drop (from 655,000 pounds to 385,000 pounds) in the Marquette‐Munising area (S‐4), and a small decrease (from 141,000 pounds to 138,000 pounds) in the Black River‐Ontonagon district (S‐2). Among the remaining districts the average yearly take increased from 322,000 pounds in 1891–1908 to 354,000 pounds in 1929–1943 at Isle Royal (S‐1), from 428,000 pounds to 501,000 pounds in the Grand Marais district (S‐5), and from 422,000 pounds to 506,000 pounds in the Keweenaw area (S‐3). These changes in the catch resulted in a westward shifting of production centers. Districts S‐1, S‐2, and S‐3 which together contributed only 30.7 percent of the 1891–1908 catch accounted for 48.4 percent of the take in 1929–1943. The 1929–1949 production in all districts exhibited periodic fluctuations that were characterized by peaks in the middle 1930ˈs and middle 1940ˈs. The indices of abundance or availability as computed from records of the catch of lake trout per unit of fishing effort showed periodic fluctuations in all districts of the State of Michigan waters similar to those of production (the peaks and the intervening minima fell a little earlier in the curves of abundance than in the production curves). For the combined districts the abundance of lake trout, expressed as a percentage of the 1929–1943 mean, stood at 108 in 1929, dropped to 100 in 1931, rose to a 21‐year high of 137 in 1934, decreased to 80 in 1940, increased again to 107 in 1944 and then fell to the 21‐year low of 65 in 1949 (this last decline was interrupted by a small increase in 1947). The 1929–1949 fluctuations in abundance were similar in the 5 mainland districts (S‐2 through S‐6). The coefficients of correlation (r) were significant for all 10 pairings and those for the 4 easterly districts (S‐3 through S‐6) were extremely high (p < 0.001 for all 6 values). Thus we have evidence that the fishermen along the mainland exploit common stocks or stocks in which the factors controlling availability are the same or subject to closely similar fluctuations. The fluctuations in abundance in S‐1 were correlated significantly (p < 0.05) with those in S‐2 but otherwise appeared to be independent of conditions along the mainland. The distinctly cyclic fluctuations that characterized the statistics on production and abundance were much less apparent in the 1929–1949 data on fishing intensity in the State of Michigan districts. In districts S‐3, S‐4, and S‐5 a possible tendency toward a cyclic fluctuation seems to have been obscured by a long‐term upward trend that was becoming stronger toward the end of the 21‐year period. For the combined districts the level of fishing pressure was consistently high after 1943. Over the 6‐year period, 1944–1949, fishing intensity expressed as a percentage of the 1929–1943 mean averaged 142; for the most recent 4 years, 1946–1949 the average intensity index was 151. On the whole, the 1929–1949 production of lake trout in the State of Michigan waters of Lake Superior was unreliable as an indicator of changes in abundance. The coefficient of correlation between the fluctuations of catch and abundance was, to be sure, positive and significant in S‐1 (p < 0.05) and S‐6 (p < 0.01), but in the remaining districts and for the combined districts the values of the coefficient were far below the level of significance. The failure of production to serve better as an indicator of changes in abundance can be attributed to the negative correlation that existed between abundance and fishing intensity (values of r highly significant in every district but S‐6 and for the combined districts). The relationship suggests that fishermen have increased their fishing pressure in order to maintain their production during the recent years of declining abundance. The condition of the lake trout fishery of the State of Michigan waters of Lake Superior must be termed unhealthy and the outlook for the future is not good. Production in 1949 stood at 106 percent of the 1929–1943 mean, but this level of yield was made possible only by fishing intensity that was 162 percent of average; the abundance index in 1949 was only 65. Certainly the stocks of lake trout are in a poor state to withstand the threatened inroads of sea lampreys which have been taken from all parts of Lake Superior and are known to have established spawning runs at least as far west as the Keweenaw Peninsula.

Michigan, Minnesota, Wisconsin↗

USGS1993

Forecasting contributions of lake whitefish year-classes to a Lake Superior commercial fishery from estimates of yearling abundance

We developed a simple linear regression model to forecast year-class contributions of lake whitefish Coregonus clupeaformis to the commercial harvest in the Apostle Islands region of Lake Superior. We indexed year-class strength from catches of yearling fish in bottom trawl samples. Recruitment of each year-class was measured by its relative abundance in the fishery at age 6. The relation between recruitment to the commercial fishery and year-class strength indices was positive and significant ( r 2 = 0.67, P < 0.01). The model produced reliable estimates of recruitment to the fishery within the range of the regression. Projected recruitment of the 1983–1987 year-classes to the fishery in 1989-1993 should be sufficient to sustain current levels of harvest through 1993.

North American Journal of Fisheries Management↗

USGS2009

Fishing mortality in North Carolina's southern flounder fishery: direct estimates of instantaneous fishing mortality from a tag return experiment

Estimation of harvest rates is often a critical component of fishery stock assessment and management. These assessments are often based on catch-at-age data sets generated over many years, but estimates of instantaneous fishing mortality ( F ) can also be obtained from a shorter-term tag return study. We conducted a 2-year tag return experiment to generate direct estimates of F for southern flounder Paralichthys lethostigma in a North Carolina estuary. The southern flounder supports lucrative commercial and recreational fisheries within the state and has experienced heavy fishing pressure for more than a decade. During 2005 and 2006, fish were captured and tagged with the assistance of commercial harvesters in the New River estuary. Tag returns were used to generate monthly estimates of F , which demonstrated a clear seasonal pattern that was consistent between years. Several important assumptions of the tag return model were accounted for through the use of double-tagged individuals, the distribution of both high- and standard-reward tags, and the completion of an independent controlled experiment to evaluate mortality related to tagging. Annual estimates of F exceeded the short-term management target in both years. Residual patterns suggest that the estimates may actually have been biased low, possibly due to delayed mixing of tagged fish. Thus, despite recently amended fishery regulations, F in the North Carolina southern flounder gill-net fishery still has the potential to greatly exceed targeted levels, which may delay stock recovery. Tag return studies can provide reliable (and nearly real-time) information about F and natural mortality as long as the experimental design addresses specific assumptions related to tagging-induced mortality, tag shedding, and nonreporting of tags.

North Carolina↗

USGS1993

Incidental catch of marine birds in the north pacific high seas driftnet fisheries in 1990

The incidental take of marine birds was estimated for the following North Pacific driftnet fisheries in 1990: Japanese squid, Japanese large-mesh, Korean squid, and Taiwanese squid and large-mesh combined. The take was estimated by assuming that the data represented a random sample from an unstratified population of all driftnet fisheries in the North Pacific. Estimates for 13 species or species groups are presented, along with some discussion of inadequacies of the design. About 416,000 marine birds were estimated to be taken incidentally during the 1990 season; 80% of these were in the Japanese squid fishery. Sooty Shearwaters, Short-tailed Shearwaters, and Laysan Albatrosses were the most common species in the bycatch.Regression models were also developed to explore the relations between bycatch rate of three groups--Black-footed Albatross, Laysan Albatross, and 'dark' shearwaters--and various explanatory variables, such as latitude, longitude, month, vessel, sea surface temperature, and net soak time (length of time nets were in the water). This was done for only the Japanese squid fishery, for which the most complete information was available. For modelling purposes, fishing operations for each vessel were grouped into 5-degree blocks of latitude and longitude.Results of model building indicated that vessel had a significant influence on bycatch rates of all three groups. This finding emphasizes the importance of the sample of vessels being representative of the entire fleet. In addition, bycatch rates of all three groups varied spatially and temporally. Bycatch rates for Laysan Albatrosses tended to decline during the fishing season, whereas those for Black-footed Albatrosses and dark shearwaters tended to increase as the season progressed. Bycatch rates were positively related to net soak time for Laysan Albatrosses and dark shearwaters. Bycatch rates of dark shearwaters were lower for higher sea surface temperatures.

International North Pacific Fisheries Commission B↗

USGS2025

Complexity and integration of recreational fisheries

Recreational fisheries are interconnected, complex, adaptive systems characterized by multiple direct and indirect interactions among ecological and human subsystems. This is important for many reasons, including that feedbacks between the social and ecological dimensions lead to difficult-to-predict, often entirely unexpected, outcomes and because many management and governance systems have multiple objectives that can involve social (e.g. fisher satisfaction), economic (e.g. license revenue), and ecological (e.g. fish conservation) dimensions. Embracing a social-ecological-system perspective can usher in an improved era of recreational fisheries science and management. Interdisciplinary approaches that unite experts across disciplines (e.g. social and ecological sciences) to create a unique theoretical, conceptual, and methodological identity are needed to gather crucial information from recreational fishers, quantify and predict fisher behaviours and outcomes from these behaviours, and integrate these findings into fisheries management. In this chapter, we lay the conceptual foundation for recreational fisheries as coupled social-ecological systems that are also complex and adaptive, and discuss the interdisciplinary approach to operationalize this book’s vision.

Book chapter↗

USGS2011

Shrimp trawlers as a local attractor of seabirds in nearshore waters of South Carolina, USA

Shrimp trawling is common throughout the southeastern and Gulf of Mexico coasts of the USA and is the primary contributor to fisheries discards in these regions. Tens of thousands of nearshore seabirds nest near shrimp trawling grounds in the USA, but to date, there has been no assessment of the relationship between seabirds and shrimp trawlers. We examined the taxonomic composition of bycatch, rate at which seabirds scavenged bycatch, and energy density of discarded bycatch in a nearshore commercial shrimp fishery. Bycatch was primarily comprised of demersal fish that are not typically accessible to the plunge-diving and surface-feeding seabirds that occur in the area. Hence, seabird diets in the region appear to be broadened taxonomically by the availability of discards. Results from discard experiments indicated that 70% of the nearly 5,500 items discarded by hand were scavenged by seabirds and that the fate of a discarded item was most strongly predicted by its taxonomic order. Laughing gulls scavenged the greatest proportion of discards, although brown pelicans were the only species to scavenge more discards than predicted based upon their abundance. Because this is the first such study in the region, it is difficult to ascertain the extent or intensity of the impact that discards have on nearshore seabirds. Nonetheless, our results suggest that it will be difficult for managers to clearly understand fluctuations in local seabird population dynamics without first understanding the extent to which these species rely upon discards. This may be especially problematic in situations where seabird populations are recovering following natural or anthropogenic stressors.

South Carolina↗

USGS2014

Inland capture fishery contributions to global food security and threats to their future

Inland fish and fisheries play important roles in ensuring global food security. They provide a crucial source of animal protein and essential micronutrients for local communities, especially in the developing world. Data concerning fisheries production and consumption of freshwater fish are generally inadequately assessed, often leading decision makers to undervalue their importance. Modification of inland waterways for alternative uses of freshwater (particularly dams for hydropower and water diversions for human use) negatively impacts the productivity of inland fisheries for food security at local and regional levels. This paper highlights the importance of inland fisheries to global food security, the challenges they face due to competing demands for freshwater, and possible solutions.

Global Food Security↗

USGS2025

Mahi-mahi metacouplings: Quantifying human–nature interactions in dolphinfish (Coryphaena hippurus) fisheries

Fisheries encompass humans and fish, but fisheries researchers rarely model human–nature interactions over space and time. I filled this information gap for dolphinfish (Coryphaena hippurus), a popular, widely distributed species that supports industrial, artisanal, recreational, and subsistence fisheries. Dolphinfish human–nature interactions showed a long-term up-and-down pattern in 1950–2019. Recent declines in catch mirror decreases in abundance and size that have been observed in parts of the species’ range. This research provides a robust perspective on the recreational, economic, cultural, and nutritional significance of dolphinfish while creating an approach for evaluating human–nature interactions in fisheries worldwide.

Global Sustainability↗

USGS2016

Using standardized fishery data to inform rehabilitation efforts

Lakes and reservoirs progress through an aging process often accelerated by human activities, resulting in degradation or loss of ecosystem services. Resource managers thus attempt to slow or reverse the negative effects of aging using a myriad of rehabilitation strategies. Sustained monitoring programs to assess the efficacy of rehabilitation strategies are often limited; however, long-term standardized fishery surveys may be a valuable data source from which to begin evaluation. We present 3 case studies using standardized fishery survey data to assess rehabilitation efforts stemming from the Nebraska Aquatic Habitat Plan, a large-scale program with the mission to rehabilitate waterbodies within the state. The case studies highlight that biotic responses to rehabilitation efforts can be assessed, to an extent, using standardized fishery data; however, there were specific areas where minor increases in effort would clarify the effectiveness of rehabilitation techniques. Management of lakes and reservoirs can be streamlined by maximizing the utility of such datasets to work smarter, not harder. To facilitate such efforts, we stress collecting both biotic (e.g., fish lengths and weight) and abiotic (e.g., dissolved oxygen, pH, and turbidity) data during standardized fishery surveys and designing rehabilitation actions with an appropriate experimental design.

Nebraska↗

USGS2022

African penguins and localized fisheries management: Response to Butterworth and Ross-Gillespie

We present a response to Butterworth and Ross-Gillespie's (2022) comment on our perspectives on how forage fish fisheries are impacting the endangered African penguin ( Sphenicus demersus ), and corresponding management options. Butterworth and Ross-Gillespie overstate model uncertainties and downplay the clear ecological and conservation significance of the fisheries closure experiment. We demonstrate that their criticism of “pseudo-replication” is weak, and not in line with their own analyses nor with the interpretations of many international scientific review panels commissioned by the government of South Africa to evaluate experimental results. Their comment does not alter our fundamental conclusions that forage fisheries operating near penguin breeding colonies compete with the birds for food resources, are detrimental to the penguin's population health, and are impeding recovery. Given that sardines are depleted (DFFE, 2021) and the African penguin is approaching a conservation crisis, we reiterate our position that continuing the precautionary approach of closures at the local scale of central-place foraging penguins is warranted to facilitate their population growth under fisheries management goals to conserve and maintain ecosystem functions.

ICES Journal of Marine Science↗

USGS2022

Genetic assignment of fisheries bycatch reveals disproportionate mortality among Alaska Northern Fulmar breeding colonies

Global fisheries kill millions of seabirds annually through bycatch, but little is known about population-level impacts, particularly in species that form metapopulations. U.S. North Pacific groundfish fisheries catch thousands of Northern Fulmars ( Fulmarus glacialis rodgersii ) each year, making fulmars the most frequently caught seabird in federally managed U.S. fisheries. Here, we used genetic stock identification to assign 1,536 fulmars sampled as bycatch to one of four Alaska breeding colonies and quantified the similarity of bycatch locations at sea among colonies. We found disproportionately high bycatch from the Pribilof Islands (6% of metapopulation, 23% of bycatch), and disproportionately low bycatch from Chagulak Island (34% of metapopulation, 14% of bycatch). Overlap between fisheries and colony-specific foraging areas diverge more during the summer breeding season, leading to greater differences in bycatch susceptibility. Contemporary and historical gene flow likely contributes to low genetic differentiation among colonies (F ST = 0.003–0.01), yet these values may not represent present connectivity. Our findings illustrate how genetic stock identification can link at-sea threats to colonies and inform management to reduce bycatch from impacted colonies.

Alaska↗