Fisheries Data Collection and Analysis
The duties of Fisheries Section staff are quite diverse, but collection and analysis of biological data remains one of the most important. These data advance a strong foundation of science-based recommendations needed to effectively manage fish populations and the fisheries they create, while also conserving Maine’s diverse range of native species.
We collect data to:
- Evaluate the status of, and detect any changes in, fish populations including Species of Greatest Conservation Need
- Assess effectiveness of regulations and stocking programs
- Determine angler use, success, and changes in preferences and behaviors
- Investigate changes in the environment
- Understand public attitudes and desires
We use this information to guide MDIFW decisions around conservation and sport fishery enhancement, and we also share it with other agencies, conservation partners, and the public.
Data Collection Priorities
Maine has a wealth of water resources providing virtually unlimited fishing opportunities; but with a limited staff, we need to prioritize how frequently we collect data on each water body.
We survey many of the state’s largest and most important waters on a routine basis. For decades, we have conducted annual studies on landlocked Atlantic salmon in Sebago Lake and West Grand Lake to monitor changes in growth. We typically survey other remote waters, like those in the Allagash Wilderness Waterway, less frequently, and sample other smaller waters more opportunistically, or when specific issues arise that warrant investigation.
Staff also heavily rely on emerging information provided by the public, either out in the field (such as while conducting creel surveys) or through other communications. Often, this is how we first hear about new fish introductions, changes in sport fisheries, and other things that may have emerged since we last sampled a particular waterbody.
Putting the Data to Work
In many cases, we collect data over time to monitor trends and evaluate the relative status of a fishery or population. After analyzing the data and comparing it to historical data (if available), regional staff develop management recommendations and work closely with the Management Section Supervisor to write well thought out annual and quarterly work plans that:
- Address local public concerns
- Strongly reflect Department planning priorities
- Can accommodate unanticipated urgent needs, like responding to a new infestation that threatens an important fishery
- In most instances, waters that are routinely monitored or sampled are more actively managed to achieve some level of fish quality and angler success, and those supported by a formal management plan may have very specific fishery attribute objectives.
- If a fishery is not meeting objectives, there are several options to consider. For example, if fish condition is unhealthy or declining in a stocked fishery, Division staff may elect to reduce the stocking rate. Or if we observed the same problem in a wild population, we may adopt a regulation change giving anglers the opportunity to harvest more fish.
Sharing the Data
Biologists routinely share data and provide updates to local angling groups and other interested parties. This helps increase public awareness and support for recommended management changes and allows us to solicit feedback. The Division also publishes special project reports on the MDIFW website.
How we collect data:
- Fish Data
- Angler Data
- Water Quality Data
- Habitat Surveys
- Monitoring and Research
- Water-specific Planning
Winter and open water angler surveys provide excellent opportunities to collect length and weight data, scales for aging, and stomach contents to assess prey availability. They are also our best source of data related to angler success. But to assess the overall health of fish populations, biologists also directly sample fish throughout the open-water season using nets, traps, and other sampling gear. These methods are often more efficient and require less effort than angler surveys; and because sampling equipment is standardized and not limited to legal-sized fish, direct sampling provides better, less biased information on fish health and population structure.
Gears frequently used to sample fish in Maine
Biologists use different techniques depending on the time of year, conditions, water type (flowing water or lake/ pond), and sampling objectives. The toolbox of sampling methods is extensive and has been refined and built out over time.
|Gear and Common Application in Maine||Pros||Cons|
|Trap net – Passive gear used to sample fish when they’re close to shore in the spring and fall. Trap nets are stationary nets that extend from the shore–nearshore and guide fish into a collection area where they are free to swim until removed for biological sampling.||
|Gillnet – Passive gear used to sample fish in the pelagic zone as they swim freely throughout the water column. Gillnets are long nets, closely resembling tennis nets, with a variety of mesh sizes. They are suspended at specific locations and depths where the targeted species are most likely to occur, and capture fish as they try to swim through the net.||
|Boat/raft electrofishing – Active gear used to sample fish in nearshore environments and flowing waters that are non-wadeable. Electrofishing boats/ rafts use a generator to create an electric field in front of the boat which temporarily impairs fish so they can be netted by biologists.||
|Backpack electrofishing – Active gear used to sample fish in depths up to waist high, including flowing water and shallow areas of lakes and ponds. Backpack electrofishing units are carried like normal backpacks and include a wand (anode) and trailing cable (cathode) that create a narrow electric field in front of the operator which temporarily impairs fish so they can be netted by biologists.||
|Experimental angling – Active gear used to sample fish in a variety of habitats. Often used to sample fish in remote waters that are difficult to get traditional gear types into and/or where other gear is less efficient (e.g., sampling bass when they’re guarding nests). Fly/spinning rod and reels may be used depending on habitat and species targeted.||
|Picket weir - Passive gear used to capture fish in flowing waters, typically as they migrate upstream to spawn. A fence-like structure is assembled across the channel to stop fish from passing upstream and a trap box is placed along the fence, where there’s sufficient attraction flow, so that fish naturally move into the trap box.||
|Beach seine – Active gear used to capture fish close to shore in flowing waters (where there’s minimal flow) and lakes and ponds. Seines are long nets that hang vertically in the water and are pulled at each end to surround fish within a given area.||
|Minnow Trap – Passive gear that is used to capture small fish in flowing waters (where there’s minimal flow) and lakes and ponds. These galvanized steel traps are relatively small (< 20” long), consisting of two halves that can be disconnected and nested together for easy transport. Bait such as dog food is used to attract fish, which enter the trap through a ~1” funnel-like opening on either end of the trap.||
Biologists use angler-sourced data in conjunction with other data to develop management recommendations. In fact, angler-sourced data is often the first cue to biologists that a fishery needs additional attention. Angler surveys are time consuming to conduct, so we can only survey anglers on a limited number of waters each year; but we also recruit anglers to voluntarily collect and submit their fishing data through citizen science programs. We manage these records collectively to track water-specific performance over time.
Direct Angler Surveys
Most of the data from angler interactions is collected during the ice fishing season when biologists interview anglers on the ice during creel surveys. Biologists use the information that anglers provide on number of fish caught and number of hours fished to calculate catch rates. By combining that information with total angler use estimates (from aerial or ground angler counts), we are able to develop season-long catch and harvest estimates. Anglers are also interviewed during the open water season, but on a more limited basis in part because of other competing field work and also because the open water fishing season is much longer, so surveys would carry a higher staff commitment.
Citizen Science Submissions
Personal Fishing Logbooks
Each regional office manages a Personal Fishing Logbook Program. Volunteer anglers record when and where they fished, and how many fish they landed and harvested. These data are used to assess potential changes in fisheries that the Department might not otherwise be focused on monitoring. This program effectively expands the Department’s capacity to monitor more waters statewide.
To collect additional information from anglers, the Department installs angler kiosks or “boxes” at certain waters near parking areas and trailheads. Anglers can voluntarily fill out a survey card related to their fishing success and place it in the box to be collected by our biologists later.
Water Quality Data
The chemical and physical properties of water often dictate what fish are present and where within a waterbody they are located. This is particularly true for coldwater fish during the summer months. To maximize our chances of collecting a target species, we will often sample the water first and use those data to inform the choice and placement of fish sampling equipment.
Biologists use specialized equipment to measure dissolved oxygen and temperature throughout the water column, which can help us assess habitat suitability for different species of fish. We also typically collect pH, conductivity, alkalinity, and Secchi depth readings to glean additional water quality information which can be tracked over time and indicate larger, landscape-level habitat suitability factors. For example, a trend of warmer summer water temperatures in a brook trout stream may indicate less coldwater input from groundwater. This shift in the face of climate change would suggest reduced future capacity to support wild brook trout year-round.
We also routinely measure water depth when sampling fish populations. By collecting depths throughout the waterbody, we can identify areas that certain fish species are most likely to inhabit, and where sampling gear will be most effective. This information also helps us assess the waterbody’s carrying capacity and management potential.
Fish have evolved to occupy a wide variety of habitats, though each species requires specific habitat characteristics to successfully complete its life history requirements. A specialist species like Arctic charr requires the deep, well-oxygenated coldwater habitat provided by Maine’s 14 Arctic charr waters; whereas a generalist species like golden shiner has broader tolerances and can be found in a variety of waters. Aquatic habitat surveys help fisheries biologists assess habitat suitability for species that may occur or be introduced within a waterbody as well as where and when those species are most likely to be encountered. The intensity of a habitat survey depends on its objective. For example, a survey of degraded habitat to inform a stream habitat restoration project would be much more involved than a survey to determine the average depth of a small pond.
MDIFW biologists conduct habitat surveys in actively managed waters, including sites that are part of long-term monitoring programs. Because most naturally formed aquatic habitats are relatively static, initial survey data can often be used for several decades before any updates are needed. A standard MDIFW lake or pond habitat survey involves measuring depths throughout the waterbody, characterizing the condition of the outlet and inlet(s), identifying potential spawning and nursery habitat, identifying springs and seeps, assessing shoreline development, and classifying substrates. Within flowing waters, habitat survey methods include measurements of flow, stream width, depth, and substrate, classification of spawning substrates, and a general assessment of the riparian zone.
Monitoring and Research
Larger lakes supporting popular coldwater fisheries are typically monitored on a set schedule. Monitoring may include collection of angler data, fish data, physical habitat data, and water quality data. These high-use sport fisheries require more intensive management, rigorous monitoring, timely management adjustments, and often, responsive stocking and regulation changes to correct unfavorable conditions.
After taking corrective management actions, we follow up with evaluations to assess effectiveness. Regulation changes may need to be in effect for many years before we can detect a change in the fishery, while stocking changes (for most species, excluding the long-lived togue) can yield improvements in less time. In either case, biologists must monitor the fishery to determine if the management change resulted in the desired effect.
Sometimes the changes occurring within fisheries cannot be explained through routine monitoring data and require additional targeted research and analysis. While the Division no longer has a research group (dissolved in 2010), fisheries staff do still periodically conduct general research to address information gaps on specific waters or among several populations of the same species. In some cases, we hire temporary staff to assist with the data collection. Formal research is typically facilitated thorough the University of Maine, including the US Geological Survey’s Maine Cooperative Fish and Wildlife Research Unit (“Coop”). The Department maintains a cooperative agreement with the Coop and provides partial funding to support its research program, as well as additional project funding for MDIFW research, either conducted by the Coop or through other University programs. The Coop provides the Bureau of Resource Management with technical expertise, staff training, and at times, grant funding for research.
MDIFW is responsible for managing of over 6,000 lakes and ponds and more than 32,000 miles of flowing water. While many similarities may exist among these resources, each has unique characteristics that influence species composition, angling pressure and success, access, water quality, and management opportunities.
Fisheries biologists in each of Maine’s seven fisheries management regions focus more of their resources on popular, higher-use recreational fisheries that require regular monitoring data to attain management objectives and meet angler expectations. These more intensively managed popular fisheries are also not surprisingly subject to more public scrutiny and are viewed as ‘regional priority waters.’ Maine’s fisheries biologists spend a lot of time collecting data from priority waters so that we can develop data-driven management objectives for them.
For some priority waters, including Moosehead Lake, we have developed publicly supported comprehensive management plans that identify priorities and ground decision making, including requests from the public. This approach has proven extremely effective for decades. However, management objectives for other priority waters have been developed internally, with little organized public input, and are not well documented. In general, biologists strive to balance overall fish health (quality fish) with abundance (reasonable catch rates). While perhaps biologically sound, the lack of public input and awareness involved in this approach creates accountability concerns in places where there’s a high level of public interest and/or where competing user groups exist.
Expanding Public Involvement
One component of this strategic planning process is to develop more robust, transparent, publicly supported management plans for priority waters statewide. By involving the public in the planning process, we can ensure that stakeholder opinions and interests are considered within the overall management approach, and we can improve the public’s understanding of and investment in the outcome.
Water-specific management plans will contain measurable, realistic/attainable objectives based on recent and historical data (e.g., catch rates, size quality) that can be routinely assessed over time using standardized sampling approaches, considerate of logistical constraints. The Division will work to ensure any future management actions (including those proposed by the public) are consistent with these plans; and because the plans will outline management objectives and priorities, the public will be able to better understand the justification behind any such actions.
To facilitate public buy-in, the process for developing each water-specific plan will rely heavily on constructive public/stakeholder participation. Fisheries staff will convene a diverse public stakeholder user group composed of members that directly or indirectly benefit from the plan’s actions; and where feasible and applicable, these user groups should include all of the following:
- Open water and ice anglers
- Registered Maine Guides who frequently use the water
- Anglers who own private and commercial property near/adjacent to the water
- Local bait/tackle shop owners and other local businesses
- Other angling and conservation groups that have a strong connection to the water
As new data and information are gathered, biologists will assess how well the fishery is meeting established objectives and adjust management if necessary. To ensure continued public support, vested stakeholders may have an opportunity to review and discuss any proposed management plan changes.
Prioritizing Plan Development
Ideally, every priority water in the state would have a water-specific management plan; but given the abundance of resources throughout the state, such an endeavor is not practical, particularly during this 15-year planning period. Therefore, Fisheries Resource Supervisors will prioritize waters within their management region and schedule the development of these plans over time. Since implementation of developed plans may require additional allocation of resources, the full burden of plan development and implementation will be considered in scheduling plan development. Where distinct waterbodies share similar characteristics with nearby waterbodies, they may be grouped together and managed under a single management plan for efficiency. For example, a single management plan may be developed for a cluster of relatively small remote trout ponds that have similar species composition, angling pressure, catch rates, etc.