Search USGS⌕ Search

SEARCH · Search USGS

Results for “Fisheries Report”

Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 163 records · Page 9Linked to original sources
USGS2024

Stopover population estimate and migration ecology of Red Knots C. c. rufa at Delaware Bay, USA, 2024

Red Knots ( Calidris canutus rufa ) stop at Delaware Bay on the mid-Atlantic coast of North America during northward migration to feed on eggs of horseshoe crabs ( Limulus polyphemus ). Horseshoe crabs have been harvested for use as bait in eel ( Anguilla rostrata ) and whelk ( Busycotypus canaliculatus and Busycon carica ) fisheries since at least 1990. In the late 1990s and early 2000s, the number of Red Knots counted during aerial surveys at Delaware Bay declined, leading to conservation concern for Red Knots and shorebirds at Delaware Bay. In 2013, the Atlantic States Marine Fisheries Commission began using an Adaptive Resource Management (ARM) framework to manage the harvest of horseshoe crabs in the Delaware Bay region. The objective of the ARM framework is to manage sustainable harvest of Delaware Bay horseshoe crabs while maintaining ecosystem integrity and supporting Red Knot recovery with adequate stopover habitat. The ARM framework thus requires annual estimates of horseshoe crab population size and Red Knot stopover population size to recommend annual harvest quotas. We estimated the passage population of Red Knots at Delaware Bay in 2024 using a mark-recapture-resight investigation. We used a Bayesian analysis of a Jolly-Seber model, which accounts for turnover in the population and the probability of detection during surveys. The estimated passage population size in 2024 was 46,127 (95% credible interval: 39,286–57,799), an increase from 2023 (39,361 [33,724–47,556]). Since 2019, the stopover population has fluctuated between approximately 39,000 and 46,000, and appears stable given the broad overlap in the confidence intervals of the annual population estimates. The 2024 Red Knot stopover population estimate will inform decision making in the next horseshoe crab management cycle of the Atlantic States Marine Fisheries Commission.

Delaware, New Jersey↗
USGS2023

Red Knot stopover population size and migration ecology at Delaware Bay, USA, 2023

Red Knots ( Calidris canutus rufa ) stop at Delaware Bay on the mid-Atlantic coast of North America during northward migration to feed on eggs of horseshoe crabs ( Limulus polyphemus ). We conducted a mark-recapture-resight investigation to estimate the passage population of Red Knots at Delaware Bay in 2023. We used a Bayesian analysis of a Jolly-Seber model, which accounts for turnover in the population and the probability of detection during surveys. The 2023 passage population size was estimated at 39,361 (95% credible interval: 33,724–47,556). Although there is broad overlap in the credible intervals for population estimates from 2020–2023, the population estimate for 2023 was below 40,000 birds for only the second time since 2011. Horseshoe crabs have been harvested for use as bait in eel ( Anguilla rostrata ) and whelk ( Busycon ) fisheries since at least 1990. In the late 1990s and early 2000s, the number of Red Knots counted during aerial surveys at Delaware Bay declined from ~50,000 to ~13,000 and some avian conservation biologists hypothesized that horseshoe crab harvest levels in the 1990s prevented sufficient refueling for successful migration to the Arctic breeding grounds, reproduction, and survival for the remainder of the annual cycle. Since 2013, the harvest of horseshoe crabs in the Delaware Bay region has been managed using an Adaptive Resource Management (ARM) framework. The objective of the ARM framework is to manage sustainable harvest of Delaware Bay horseshoe crabs while maintaining ecosystem integrity and supporting Red Knot recovery with adequate stopover habitat for Red Knots and other migrating shorebirds. For annual harvest recommendations, the ARM framework requires annual estimates of horseshoe crab population size and the Red Knot stopover population size. The 2023 population size estimate will inform harvest recommendations in the next management cycle for decision making by the Atlantic States Marine Fisheries Commission.

Delaware, New Jersey↗
USGS2017

The contribution of lakes to global inland fisheries harvest

Freshwater ecosystems provide numerous services for communities worldwide, including irrigation, hydropower, and municipal water; however, the services provided by inland fisheries – nourishment, employment, and recreational opportunities – are often comparatively undervalued. We provide an independent estimate of global lake harvest to improve biological and socioeconomic assessments of inland fisheries. On the basis of satellite-derived estimates of chlorophyll concentration from 80,012 globally distributed lakes, lake-specific fishing effort based on human population, and output from a Bayesian hierarchical model, we estimated that the global lake fishery harvest in the year 2011 was 8.4 million tons (mt). Our calculations excluded harvests from highly productive rivers, wetlands, and very small lakes; therefore, the true cumulative global fishery harvest from all freshwater sources likely exceeded 11 mt as reported by the Food and Agriculture Organization of the United Nations (FAO). This putative underestimate by the FAO could diminish the perceived importance of inland fisheries and perpetuate decisions that adversely affect these fisheries and millions of people.

Frontiers in Ecology and the Environment↗
USGS2019

Report of the River Master of the Delaware River for the period December 1, 2009–November 30, 2010

A Decree of the Supreme Court of the United States, entered June 7, 1954, established the position of Delaware River Master within the U.S. Geological Survey. In addition, the Decree authorizes diversion of water from the Delaware River Basin and requires compensating releases from certain reservoirs, owned by New York City, to be made under the supervision and direction of the River Master. The Decree stipulates that the River Master will furnish reports to the Court, not less frequently than annually. This report is the 57th Annual Report of the River Master of the Delaware River. It covers the 2010 River Master report year, the period from December 1, 2009, to November 30, 2010. During the report year, precipitation in the upper Delaware River Basin was 49.38 inches or 112 percent of the long-term average. Combined storage in Pepacton, Cannonsville, and Neversink Reservoirs remained high much of the year and did not decline below 80 percent of combined capacity until September 2010. A lower basin drought warning was issued by the Delaware River Basin Commission on September 24, 2010. It automatically ended on October 31, 2010, when the reservoir contents rose above drought levels, due in large part to heavy rainfall during the last week of September. River Master operations during the year were conducted as stipulated by the Decree and the Flexible Flow Management Program. Diversions from the Delaware River Basin by New York City and New Jersey were in full compliance with the Decree. Reservoir releases were made as directed by the River Master at rates designed to meet the flow objective for the Delaware River at Montague, New Jersey, on 81 days during the report year. Interim Excess Release Quantity and conservation releases, designed to relieve thermal stress and protect the fishery and aquatic habitat in the tailwaters of the reservoirs, were made during the report year. The quality of water in the Delaware Estuary between Trenton, New Jersey, and Reedy Island Jetty, Delaware, was monitored at various locations. Data on water temperature, specific conductance, dissolved oxygen, and pH were collected continuously by electronic instruments at four sites.

Delaware, Maryland, New Jersey, New York, Pennsylv↗
USGS2024

Report of the River Master of the Delaware River for the period December 1, 2016–November 30, 2017

Executive Summary A Decree of the Supreme Court of the United States, entered June 7, 1954 ( New Jersey v. New York , 347 U.S. 995), established the position of Delaware River Master within the U.S. Geological Survey. In addition, the Decree authorizes the diversion of water from the Delaware River Basin and requires compensating releases from certain reservoirs owned by New York City be made under the supervision and direction of the River Master. The Decree stipulates that the River Master provide reports to the Court, not less frequently than annually. This report is the 64th annual report of the River Master of the Delaware River. The report covers the 2017 River Master report year, from December 1, 2016, to November 30, 2017. During the report year, precipitation in the upper Delaware River Basin was 47.85 inches or 108 percent of the long-term average. On December 1, 2016, combined useable storage in the New York City reservoirs in the upper Delaware River Basin was 110.115 billion gallons or 40.7 percent of combined storage capacity, the lowest combined storage of the 2017 report year. The reservoirs were at about 100 percent of useable capacity on May 31, 2017. Combined storage remained above 80 percent of combined capacity until September 2017. A lower basin drought watch issued by the Delaware River Basin Commission in 2016 extended from the beginning of this report year to January 18, 2017. The drought watch was ended on January 18, 2017, due to increased precipitation in December 2016. River Master operations during the year were conducted as stipulated by the Decree and the Flexible Flow Management Programs. Diversions from the Delaware River Basin by New York City and New Jersey fully complied with the Decree. Reservoir releases were made as directed by the River Master at rates designed to meet the flow objective for the Delaware River at Montague, New Jersey (N.J.), on 52 days during the report year. Interim Excess Release Quantity and conservation releases, designed to relieve thermal stress and protect the fishery and aquatic habitat in the tailwaters of the reservoirs, were made during the report year. Excess Release Quantity and Interim Excess Release Quantity Bank releases were also made during the report year. The water quality in the Delaware River estuary between the streamgages at Trenton, N.J., and Reedy Island Jetty, Delaware, was monitored at various locations. The data on water temperature, specific conductance, dissolved oxygen, and pH were collected continuously by electronic instruments at four sites.

New Jersey, New York, Pennsylvania↗
USGS2020

Report of the River Master of the Delaware River for the period December 1, 2010–November 30, 2011

A Decree of the Supreme Court of the United States, entered June 7, 1954, established the position of Delaware River Master within the U.S. Geological Survey. In addition, the Decree authorizes diversion of water from the Delaware River Basin and requires compensating releases from certain reservoirs, owned by New York City, to be made under the supervision and direction of the River Master. The Decree stipulates that the River Master will furnish reports to the Court, not less frequently than annually. This report is the 58th Annual Report of the River Master of the Delaware River. It covers the 2011 River Master report year, the period from December 1, 2010, to November 30, 2011. During the report year, precipitation in the upper Delaware River Basin was 71.43 inches or 162 percent of the long-term average. On December 1, 2010, combined usable storage in the New York City reservoirs in the upper Delaware River Basin was 230.430 billion gallons or 85.1 percent of combined storage capacity. The reservoirs were at about 100 percent of usable capacity on May 31, 2011. Combined storage remained high (above 80 percent combined capacity) through November 2011. River Master operations during the year were conducted as stipulated by the Decree and the Flexible Flow Management Program. Diversions from the Delaware River Basin by New York City and New Jersey were in full compliance with the Decree. Reservoir releases were made as directed by the River Master at rates designed to meet the flow objective for the Delaware River at Montague, New Jersey, on 5 days during the report year (July 24–28, 2011). Conservation releases, designed to relieve thermal stress and protect the fishery and aquatic habitat in the tailwaters of the reservoirs, were also made during the report year. The quality of water in the Delaware Estuary between Trenton, New Jersey, and Reedy Island Jetty, Delaware, was monitored at various locations. Data on water temperature, specific conductance, dissolved oxygen, and pH were collected continuously by electronic instruments at four sites.

New York, New Jersey, Pennsylvania↗
USGS2026

Investigation of fish communities in natural channel sections of the Mohawk River, New York

Little is known about the natural resources in the natural channel sections of the Mohawk River between Rome and Frankfort, New York, where the river channel runs separately from and parallel to the Erie Canal. This river section runs through multiple locations that are listed as active remediation sites under New York’s Inactive Hazardous Waste Disposal Site Program and has negligible public or commercial access. As a result, there is minimal recreational usage of this river section, and efforts to conduct biological sampling have been limited. To better understand the composition of fish communities and contaminant concentrations in the natural channel of the Mohawk River, the U.S. Geological Survey, in cooperation with the New York State Department of Environmental Conservation, sampled resident fish in the 34-kilometer section from the mouth of Oriskany Creek downstream to Frankfort. Fish communities were sampled using boat electrofishing during 2021, 2023, and 2024 across multiple reaches within this section. These data were used to estimate species richness (number of species), relative abundance and biomass (catch rates), population size structure (distribution of lengths), and fish condition (a proxy for health). Some gamefish specimens were also analyzed to determine contaminant concentrations in fish tissue. A total of 1,531 individual fish and 38 fish species were captured across all surveys. Seventeen of the 38 (45 percent) species were classified as native to the Mohawk River watershed, whereas 21 of the 38 (55 percent) species were classified as nonnative. Some popular gamefish species such as largemouth bass ( Micropterus salmoides ) and smallmouth bass ( Micropterus dolomieu ) were abundant in most reaches, whereas others such as walleye ( Sander vitreus ) and northern pike ( Esox lucius ) were found sporadically. Only one round goby ( Neogobius melanostomus ) was captured, indicating that this high-profile invasive species remains uncommon in this habitat. A backwater reach had the greatest relative abundance and condition of many species. This indicates connected lentic habitats such as oxbows and backwaters may be important nursery and refuge areas in the aquatic ecosystem. Polychlorinated biphenyl (PCB) concentrations in fish tissue were highly elevated relative to the New York State Department of Health (NYSDOH) fish consumption “don’t eat” advisory guideline. Some specimens exceeded the guideline by an order of magnitude or more, particularly those from a localized area downstream from the Utica Harbor Dam. Concentrations of perfluorooctanesulfonic acid (PFOS) often approached the NYSDOH “don’t eat” consumption guideline but only one sample exceeded the guideline. Concentrations of other contaminants such as mercury and pesticides were consistently measured at less than the “don’t eat” consumption guidelines. These data indicate PCBs remain the primary contaminant of concern in the natural channel of the Mohawk River and are readily bioaccumulating in aquatic organisms despite prior remediation measures. Taken together, the findings in this report are intended to inform future decisions related to fisheries management, public access, recreational usage, and fish consumption advisories.

New York↗
USGS2022

Report of the River Master of the Delaware River for the period December 1, 2011–November 30, 2012

A Decree of the Supreme Court of the United States, entered June 7, 1954, established the position of Delaware River Master within the U.S. Geological Survey. In addition, the Decree authorizes diversion of water from the Delaware River Basin and requires compensating releases from certain reservoirs, owned by New York City, to be made under the supervision and direction of the River Master. The Decree stipulates that the River Master will furnish reports to the Court, not less frequently than annually. This report is the 59th annual report of the River Master of the Delaware River. It covers the 2012 River Master report year, the period from December 1, 2011 to November 30, 2012. During the report year, precipitation in the upper Delaware River Basin was 43.35 inches or 97 percent of the long-term average. Combined storage in the Pepacton, Cannonsville, and Neversink Reservoirs remained high through late May, declined from then until mid-September, decreasing below 80 percent of combined capacity in late August, increased in late October, and decreased slightly in November 2012. Delaware River Master operations during the year were conducted as stipulated by the Decree and the Flexible Flow Management Program. Diversions from the Delaware River Basin by New York City and New Jersey were in full compliance with the Decree. Reservoir releases were made as directed by the River Master at rates designed to meet the flow objective for the Delaware River at Montague, New Jersey, on 52 days during the report year. Interim Excess Release Quantity and conservation releases, designed to relieve thermal stress and protect the fishery and aquatic habitat in the tailwaters of the reservoirs, were also made during the report year. An agreement was signed on October 25, 2012, to increase discharge mitigation releases from the Neversink Reservoir due to potential impacts from Hurricane Sandy. The quality of water in the Delaware River estuary between Trenton, New Jersey, and Reedy Island Jetty, Delaware, was monitored at various locations. Data on water temperature, specific conductance, dissolved oxygen, and pH were collected continuously by electronic instruments at four sites.

New Jersey, New York, Pennsylvania↗
USGS2022

Report of the River Master of the Delaware River for the period December 1, 2012–November 30, 2013

A Decree of the Supreme Court of the United States, entered June 7, 1954, established the position of Delaware River Master within the U.S. Geological Survey. In addition, the Decree authorizes diversion of water from the Delaware River Basin and requires compensating releases from certain reservoirs, owned by New York City, to be made under the supervision and direction of the River Master. The Decree stipulates that the River Master will furnish reports to the Court, not less frequently than annually. This report is the 60th annual report of the River Master of the Delaware River. It covers the 2013 River Master report year, the period from December 1, 2012 to November 30, 2013. During the report year, precipitation in the upper Delaware River Basin was 44.50 inches or 100 percent of the long-term average. Combined storage in the Pepacton, Cannonsville, and Neversink Reservoirs remained high until October 2013 when it decreased below 80 percent combined capacity. The lowest combined storage of the report year was 70.2 percent of combined capacity on November 26, 2013. Delaware River Master operations during the year were conducted as stipulated by the Decree and the Flexible Flow Management Program. Diversions from the Delaware River Basin by New York City and New Jersey were in full compliance with the Decree. Reservoir releases were made as directed by the River Master at rates designed to meet the Montague flow objective for the Delaware River at the Montague, New Jersey streamgage on 71 days during the report year. Interim Excess Release Quantity and conservation releases, designed to relieve thermal stress and protect the fishery and aquatic habitat in the tailwaters of the reservoirs, were also made during the report year. An agreement was signed on July 16, 2013 to temporarily increase releases to provide thermal protection below Cannonsville Reservoir. The quality of water in the Delaware River estuary between streamgages at Trenton, New Jersey, and Reedy Island Jetty, Delaware, was monitored at several locations. Data on water temperature, specific conductance, dissolved oxygen, and pH were collected continuously by electronic instruments at four sites.

Delaware, New Jesey, New York, Pennsylvania↗
USGS2024

Report of the River Master of the Delaware River for the period December 1, 2013–November 30, 2014

Executive Summary A Decree of the Supreme Court of the United States, entered June 7, 1954 ( New Jersey v. New York , 347 U.S. 995), established the position of Delaware River Master within the U.S. Geological Survey. In addition, the Decree authorizes the diversion of water from the Delaware River Basin and requires compensating releases from specific reservoirs owned by New York City to be made under the supervision and direction of the River Master. The Decree stipulates that the River Master provide reports to the Court, not less frequently than annually. This report is the 61st annual report of the River Master of the Delaware River. The report covers the 2014 River Master report year, which is the period from December 1, 2013, to November 30, 2014. During the report year, precipitation in the upper Delaware River Basin was 42.40 inches or 95 percent of the long-term average. On December 1, 2013, combined useable storage in New York’s Pepacton, Cannonsville, and Neversink Reservoirs in the upper Delaware River Basin was 200.133 billion gallons or 73.9 percent of the combined capacity of 270.8 billion gallons. The reservoirs were at about 99.7 percent of usable capacity on May 31, 2014. Combined storage in the Pepacton, Cannonsville, and Neversink Reservoirs decreased below 80 percent of combined capacity in late August. The lowest combined storage was 151.730 billion gallons or 56 percent of combined capacity on November 24, 2014. Delaware River Master operations during the year were conducted as stipulated by the Decree and the Flexible Flow Management Program. Diversions from the Delaware River Basin by New York City and the State of New Jersey fully complied with the Decree. Reservoir releases were made as directed by the River Master at rates designed to meet the flow objective for the Delaware River at Montague, New Jersey, on 94 days during the report year. Interim Excess Release Quantity and conservation releases, designed to relieve thermal stress and protect the fishery and aquatic habitat in the tailwaters of the reservoirs, were also made during the report year. Water quality in the Delaware River estuary between streamgages at Trenton, New Jersey, and Reedy Island Jetty, Delaware, was monitored at several locations. Data on water temperature, specific conductance, dissolved oxygen, and pH were collected continuously by electronic instruments at four locations.

New Jersey, New York, Pennsylvania↗
USGS2024

Report of the River Master of the Delaware River for the period December 1, 2014–November 30, 2015

Executive Summary A Decree of the Supreme Court of the United States, entered June 7, 1954 ( New Jersey v. New York , 347 U.S. 995), established the position of Delaware River Master within the U.S. Geological Survey. In addition, the Decree authorizes the diversion of water from the Delaware River Basin and requires compensating releases from specific reservoirs owned by New York City be made under the supervision and direction of the River Master. The Decree stipulates that the River Master provide reports to the Court, not less frequently than annually. This report is the 62nd annual report of the River Master of the Delaware River. This report covers the 2015 River Master report year, which is the period from December 1, 2014, to November 30, 2015. During the report year, precipitation in the upper Delaware River Basin was 42.22 inches or 95 percent of the long-term average. The combined storage remained above 80 percent of the combined capacity until August 2015. The lowest combined storage of the report year was 57 percent of the total combined capacity on December 1, 2014. Delaware River Master operations during the year were conducted as stipulated by the Decree and the Flexible Flow Management Program. Diversions from the Delaware River Basin by New York City and New Jersey fully complied with the Decree. The reservoir releases were made as directed by the River Master at rates designed to meet the flow objective for the Delaware River at Montague, New Jersey, on 72 days during the report year. Interim Excess Release Quantity and conservation releases, designed to relieve thermal stress and protect the fishery and aquatic habitat in the tailwaters of the reservoirs, were also made during the report year. Water quality in the Delaware River estuary between the streamgages at Trenton, New Jersey, and Reedy Island Jetty, Delaware, was monitored at several locations. Data on water temperature, specific conductance, dissolved oxygen, and pH were collected continuously by electronic instruments at four sites.

Delaware, New Jersey New York, Pennsylvania↗
USGS2024

Report of the River Master of the Delaware River for the period December 1, 2015 - November 30, 2016

Executive Summary A Decree of the Supreme Court of the United States, entered June 7, 1954 ( New Jersey v. New York , 347 U.S. 995), established the position of Delaware River Master within the U.S. Geological Survey. In addition, the Decree authorizes the diversion of water from the Delaware River Basin and requires compensating releases from reservoirs owned by New York City to be made under the supervision and direction of the River Master. The Decree stipulates that the River Master provide reports to the Court not less frequently than annually. This report is the 63rd annual report of the River Master of the Delaware River. The report covers the 2016 River Master report year, which is the period from December 1, 2015, to November 30, 2016. During the report year, precipitation in the upper Delaware River Basin was 38.6 inches or 87 percent of the long-term average. Combined storage remained high (above 80 percent of combined capacity) for much of the year and did not decline below 80 percent of combined capacity until August 2016. The lowest combined storage was 106.406 billion gallons or 39 percent of combined capacity on November 28, 2016. Delaware River Basin Commission Resolution 2016–07 necessitated a basinwide drought watch on November 23, 2016. The drought watch continued through the remainder of the 2016 report year. Delaware River Master operations during the year were conducted as stipulated by the Decree and the Flexible Flow Management Program. New York City and New Jersey fully complied with the terms of the Decree and, during drought watch conditions, with the Delaware River Basin Commission Resolution 2016–07 terms. Diversions from the Delaware River Basin by New York City and New Jersey fully complied with the Decree. The reservoir releases were made as directed by the River Master at rates designed to meet the flow objective for the Delaware River at Montague, New Jersey, on 126 days during the report year. Interim Excess Release Quantity and conservation releases, designed to relieve thermal stress and protect the fishery and aquatic habitat in the tailwaters of the reservoirs, were also made during the report year. Water quality in the Delaware River estuary between the streamgages at Trenton, New Jersey, and Reedy Island Jetty, Delaware, was monitored at several locations. Data on water temperature, specific conductance, dissolved oxygen, and pH were collected continuously by electronic instruments at four sites.

Delaware, Maryland, New Jersey, New York, Pennsylv↗
USGS2018

New global high-resolution centerlines dataset of selected river systems

We present the first high resolution (1:20,000) river centerlines shapefiles from 50 large rivers across the world. Rivers were selected based on the criteria of having more than 1000 km length and which have been reported to have a significant contribution to global fishery production. Since large rivers often span multiple countries, the degree of changes (i.e., anthropogenic or climate derived) varies from region to region. These high-resolution layers were developed to enable researchers to delineate accurate river length, from headwaters regions to their delta and assess or visualize the ongoing changes more accurately in these river systems. Further, these polylines could be used in coordination with satellite derived environmental or landscape variables for ecological research (e.g. predicting biodiversity, estimating biomass).

Data in Brief↗
USGS1987

Dynamics of the recovery of the western Lake Erie walleye (Stizostedion vitreum vitreum) stock

After its 1957 collapse under intensive fishing and environmental stresses, the walleye (Stizostedion vitreum vitreum) stock of western Lake Erie remained low throughout the 1960s. A moratorium on both sport and commercial fishing, resulting from the 1970 discovery of mercury concentrations in walleye flesh, provided an opportunity for the development of an international interagency management plan. The quota management plan developed depended on sequential projection of the fishable stock on the basis of estimated annual recruitment and reports of total withdrawals from the stock. The fishery reopened gradually and quota management (including allocation among jurisdictions) was implemented in 1976. The stock, which had been gradually increasing as a result of relatively strong year-classes produced in 1970, 1972, and 1974, responded well to limited exploitation and produced a record year-class in 1977. Quotas were exceeded in 1978-80, but the stock continued to improve to the extent that the recommended rate of exploitation was increased in 1980 and again in 1981. As the population expanded, growth began to decline; the decline became apparent in young-of-the-year in the early 1970s and in older walleyes in the late 1970s. This trend toward progressively slower growth, which continued in the 1977 and subsequent year-classes, was accompanied by an increase in length at sexual maturity and a decrease in the percentage of female walleyes reaching sexual maturity at age III. As a net result of these changes, the proportion of mature females in the stock (an index of stock fecundity) decreased slightly during the interval 1975-84, while the estimated biomass of the standing stock rose from 9 000 to nearly 26 000 t. Both sport and commercial catches increased markedly after 1980 in Lake Erie's central basin.

Canadian Journal of Fisheries and Aquatic Sciences↗
USGS2015

Status and trends of prey fish populations in Lake Michigan, 2013

The U.S. Geological Survey Great Lakes Science Center has conducted lake-wide surveys of the fish community in Lake Michigan each fall since 1973 using standard 12-m bottom trawls towed along contour at depths of 9 to 110 m at each of seven index transects. The resulting data on relative abundance, size and age structure, and condition of individual fishes are used to estimate various population parameters that are in turn used by state and tribal agencies in managing Lake Michigan fish stocks. All seven established index transects of the survey were completed in 2013. The survey provides relative abundance and biomass estimates between the 5-m and 114-m depth contours of the lake (herein, lake-wide) for prey fish populations, as well as burbot, yellow perch, and the introduced dreissenid mussels. Lake-wide biomass of alewives in 2013 was estimated at 29 kilotonnes (kt, 1 kt = 1000 metric tonnes), which was more than three times the 2012 estimate. However, the unusually high standard error associated with the 2013 estimate indicated no significant increase in lake-wide biomass between 2012 and 2013. Moreover, the age distribution of alewives remained truncated with no alewife exceeding an age of 5. The population of age-1 and older alewives was dominated (i.e., 88%) by the 2010 and 2012 year-classes. Record low biomass was observed for deepwater sculpin (1.3 kt) and ninespine stickleback (0.004 kt) in 2013, while bloater (1.6 kt) and rainbow smelt (0.2 kt) biomasses remained at low levels. Slimy sculpin lake-wide biomass was 0.32 kt in 2013, marking the fourth consecutive year of a decline. The 2013 biomass of round goby was estimated at 10.9 kt, which represented the peak estimate to date. Burbot lake-wide biomass (0.4 kt in 2013) has remained below 3 kt since 2001. Numeric density of age-0 yellow perch (i.e., < 100 mm) was only 1 fish per ha, which is indicative of a relatively poor year-class. Lake-wide biomass estimate of dreissenid mussels in 2013 was 23.2 kt. Overall, the total lake-wide prey fish biomass estimate (sum of alewife, bloater, rainbow smelt, deepwater sculpin, slimy sculpin, round goby, and ninespine stickleback) in 2013 was 43 kt, with alewives and round gobies constituting 92% of this total.

Lake Michigan↗
USGS2012

Status and trends of prey fish populations in Lake Michigan, 2012

The U.S. Geological Survey Great Lakes Science Center has conducted lake-wide surveys of the fish community in Lake Michigan each fall since 1973 using standard 12-m bottom trawls towed along contour at depths of 9 to 110 m at each of seven index transects. The resulting data on relative abundance, size and age structure, and condition of individual fishes are used to estimate various population parameters that are in turn used by state and tribal agencies in managing Lake Michigan fish stocks. All seven established index transects of the survey were completed in 2012. The survey provides relative abundance and biomass estimates between the 5-m and 114-m depth contours of the lake (herein, lake-wide) for prey fish populations, as well as burbot, yellow perch, and the introduced dreissenid mussels. Lake-wide biomass of alewives in 2012 was estimated at 9 kilotonnes (kt, 1 kt = 1000 metric tonnes), which continues the trend of unusually low alewife biomass since 2004 but represented a 20% increase from the 2011 estimate. The age distribution of alewives larger than 100 mm was dominated (i.e., 84%) by age-2. Record low biomass was observed for several species, including bloater (0.4 kt), rainbow smelt (0.1 kt), deepwater sculpin (1.5 kt), and ninespine stickleback (0.01 kt). Slimy sculpin lake-wide biomass was 0.73 kt in 2012, which was the third consecutive year revealing a decline. Estimated biomass of round goby increased by 79% to 3 kt. Burbot lake-wide biomass (0.5 kt in 2012) has remained below 3 kt since 2001. Numeric density of age-0 yellow perch (i.e., < 100 mm) was only 2 fish per ha, which is indicative of a relatively poor year-class. Lake-wide biomass estimates of dreissenid mussels have continued to increase from 2010, from 12 to 95 kt in 2012. Overall, the total lake-wide prey fish biomass estimate (sum of alewife, bloater, rainbow smelt, deepwater sculpin, slimy sculpin, round goby, and ninespine stickleback) in 2012 was 15 kt, which represented the lowest total biomass of the time series.

Lake Michigan↗