The FMP for American Eel requires six weeks of sampling during the peak ingress of glass eels. In New Jersey, this typically begins during the month of February. Both the fyke net and the collectors are tended daily, seven days a week, at the daylight low tide. When weather or crew restrictions occur, the net is pulled from the water or tied up so that it’s not fishing. An alternate collector may remain in the water without being checked daily, if necessary. The sampling season ends when a minimum of six weeks of fyke net sampling are complete and catch numbers are at or near zero each day.

Through an analysis of commercial American eel data, it was determined that yellow eel sampling would occur during spring and fall, when catches are at their highest. The survey is conducted for eight weeks each spring (mid-April to mid-June) and fall (mid-September to mid-November).

Start and end dates for both surveys are determined based on environmental and weather conditions in the area.

The total number of glass eels caught in the fyke net is calculated daily. A subsample of 60 glass eels from the fyke net are individually weighed, measured and checked for pigmentation stage at least twice a week. No individual lengths or weights are recorded from glass eels caught in the collectors, but a total count is recorded. All green eels caught in the fyke net are individually weighed and measured, while those caught in the collectors are simply counted. All eels caught during this survey are released alive at the location where they were caught.

Sampling crews collect and record environmental parameters each time the fyke net and collectors are tended: water temperature, air temperature, pH, wind speed and direction, as well as water depth.

During the yellow eel pot survey, four strings of four pots each are set at predetermined locations on Monday, tended and reset on Wednesday and tended and pulled on Friday. Pots are baited with Atlantic menhaden (bunker). Soak times are weather dependent and range from 12-48 hours. Various environmental and climatological data are recorded when pots are set and again when pots are tended: water depth, air temperature, dissolved oxygen, water temperature, salinity and pH. Each time a string of pots is hauled in, the total number of eels caught is recorded.

Lengths and weights are collected from each yellow eel caught in the pot survey. Additionally, a small notch (fin clipping) is cut into the pectoral fin of each eel in an effort to monitor recaptures. The eels are released alive; however, a subsample is retained for additional biological sampling which involves removing the otoliths for age data. Otoliths are part of the inner ear of the eel and can be aged by counting their rings, like ageing a tree. Because this survey utilizes commercial gear in a commercially important estuary, age data collected during the yellow eel pot survey supplements the American eel biological sampling program of the commercial fishery (fishery-dependent).

Bycatch from both surveys is identified by species, counted and released.

The total number of glass eels caught during the fyke net survey fluctuates annually. Timing and rate of the annual ingress from saltwater to freshwater is dependent on many factors that vary greatly from year to year or even week to week. Ocean temperature, currents, wind rates and direction, air temperature, coastal flooding patterns and winter storm occurrence and intensity are some of the most common influences on glass eel recruitment into New Jersey waters. Winters with above average air temperatures produce an early increase in coastal water temperatures. This typically means that glass eels will begin to arrive earlier in the year while the water is still colder. As water temperatures increase, the number of glass eels moving into freshwater rivers and streams tends to decrease. Flooding and drought incidents or ice coverage can also alter the course that glass eels choose to take into freshwater. These environmental influences alter the salinity of coastal waters. When there is an influx of freshwater from rain or snowstorms, the salinity of coastal rivers and streams goes down. Conversely, when there are periods of drought conditions with little freshwater runoff, the salinity of those water bodies goes up. Since glass eels are looking to move from saltwater into freshwater during the winter months, slight changes in salinity can alter their movements and the timing of those actions. Correlations between the lunar cycle and migration patterns are well documented and can also affect the ingress of glass eels. Some of the highest catches during the fyke net survey occur during the new or full moon. In summary, a multitude of factors alter the number of glass eels moving through the sampling locations on an annual basis.

Glass eels collected during the fyke net survey are subsampled for biological data including lengths and weights. On average, the eels sampled are 2.5 inches long and weigh a mere 0.2 grams (0.0004 pounds). Pigmentation stages are also recorded for all eels in the subsample. Glass eels are clear fish, hence the name. As they age, their bodies become pigmented in stages (1-7). Stage 1 is clear while stage 7 is the darkest and at that point they are considered a green eel. The average pigmentation of a glass eel caught in the fyke net is stage 2.

The number of glass eels collected in an artificial collector is subject to the same environmental influences as the fyke net and varies from year to year. In 2012, biologists were surprised by one single catch of over 31,000 eels in one collector! These artificial collectors have proven to be a reasonable representation of the type of structure that glass eels want to inhabit. The success of this portion of the glass eel survey has led to a long-anticipated expansion of the project which will include collecting biological data from individual eels, as opposed to just a total count of the number of eels caught in each collector.

American eels will remain in freshwater or brackish water until they reach the silver life stage and return to the ocean. The Great Bay’s abundance of small fish, insects and mollusks makes this estuary an excellent home for yellow eels. It is at this life stage that eels are commonly used as fishing bait. Since its inception in 2015, the yellow eel pot survey has collected larger catches during fall sampling each year. As water temperature increases, catch totals often decrease. Yellow eels tend to be most abundant in Great Bay when the water temperature is between 54-73 degrees Fahrenheit. While survey catches within the Great Bay vary from year to year, American eels are consistently present within the estuary, and this remains a positive sign that eels continue to endure at a local location once they’ve entered Jersey waters.

All American eels caught during the pot survey are weighed and measured. On average, the yellow eels sampled are 19 inches long and weigh 0.5 pounds. Additionally, age data is collected from a subsample of eels caught during the pot survey. Most yellow eels caught during the survey are between three and five years old, with an average age of 4.5 years old. Over the next few years, this survey will be expanded to include tagging eels with Passive Integrated Transponder (PIT) tags to collect recapture data. PIT tags are small microchips which are implanted safely in many species of animals. Each tag has a unique code associated with it. When a tagged animal is caught, the chip can be scanned to retrieve the code and biologists can determine when and where the animal was originally tagged. Length and weight measurements taken at the time of recapture are compared to initial measurements. This allows biologists to track the growth rates of the tagged species. Studying the movement patterns and growth rates of American eels is a vital part of assessing the stock within New Jersey. Additional data to be collected within the next few years include gender and presence/absence of a swim bladder nematode, Anguillicola crassus. This type of parasitic worm is common throughout the population of American eels. A healthy swim bladder is necessary to survive the exhausting migration back to the Sargasso Sea that can be thousands of miles long and take months to complete. Knowing how many eels are affected by this parasite could potentially help biologists determine how much influence their presence has on swim bladder functions and survival rates of American eels.

All life stages of American eels are subject to fishing pressure. Surveys like the ones conducted by New Jersey’s Bureau of Marine Fisheries allow biologists to learn more about the impact that recreational and commercial fishing has on New Jersey’s local eel population. Data collected from abundance surveys such as the glass and yellow eel surveys are key elements of Coastwide stock assessments. There are very few fishery-independent surveys that target American eel along the East Coast of the United States, so it is important for New Jersey to continue and expand current research on various life stages. American eels are found in marine, estuarine and freshwater habitats. Learning more about habitat requirements that allow eels to progress through all life stages successfully and return to the Sargasso Sea to spawn is critical.

While the ASMFC’s 2012 Benchmark Stock Assessment and the 2017 Update Assessment state that the American eel population is depleted, New Jersey has not seen a major decrease in the number of eels caught in either the glass or yellow eel survey. Hopefully this trend will continue, paving the way for a more robust Coastwide population in the future.