New Brunswick Salmon Council Stocking Policy
New Brunswick Salmon Council Stocking Policy
It is the policy of the New Brunswick Salmon Council (NBSC) to provide guidelines to NBSC affiliates by using “best practices” to assist in developing a stocking program. Guiding principles are that, where and when justified, wild strains of Atlantic salmon native to New Brunswick be stocked in provincial waters, providing the introduced fish do not compromise the health or genetic integrity of existing wild stocks.
The NBSC’s fish management strategies focus on responsible management of fish habitat and fish populations to promote natural reproduction of wild fish populations. Despite this, stocking is sometimes warranted to sustain specific individual populations while the root cause(s) resulting in population declines are addressed. In other words, stocking is an attempt to mitigate the effects of these root causes.
Stocking should be considered a potential element of salmon population preservation and subsequent recovery strategies, but should not be the first component of any recovery strategy that is considered or implemented. Stocking has been used historically as the default method of countering low fish populations. However, indiscriminate stocking can result in unforeseen consequences (e.g., deleterious changes in populations resulting in reduced genetic diversity). As such, the stocking of artificially reared fish must be carefully considered before incorporating stocking into a recovery plan.
Salmon rivers are varied and complex in their physical, chemical, and biological characteristics that must be carefully considered when determining the best fisheries management strategies.
Stocking, when applied improperly, can be detrimental to the natural aquatic biota and can result in a loss of resources through competition, predation, and genetic inbreeding or outbreeding. Given the cost and risks associated with fish stocking, ideally it is important that all other management options also be considered as components of a recovery plan. Unless the root causes resulting in the population decline are identified and mitigated, stocking may not achieve the goal of overall population recovery and may serve to only mask the negative impacts of the root causes.
The stocking guideline policy objective is to encourage our affiliates to use fish stocking programs that are based on sound scientific principles that minimize negative impacts to natural populations and benefit the rehabilitation of depressed stocks in an effort to ensure populations are preserved while root causes of stock decline are assessed and addressed.
Depressed population phenomenon: A fish population that has dropped below a self-sustaining level. Often referred to as the Allee Effect.
F Concept: F refers to the number of generations a stocked fish is from the wild. For example:
- An F0 fish is a wild fish that has been captured and held in captivity for a length of time to avoid mortality factors that would have been encountered in the wild during the time of captivity. When this fish is released (stocked), it is still wild and therefore an F0 fish. An example would be adult fish released in a smolt-to-adult-supplementation program (See below), or a reconditioned wild kelt (post-spawned salmon).
- An F1 fish is one, the parents of which were wild and were artificially spawned. Examples of life stages resulting from the spawning that could be stocked are, eggs planted in the gravel of nursery streams, fry releases, parr releases, smolt releases and adult releases prior to spawning.
- An F2 fish is one whose grandparents were wild. This type of program takes the F1 progeny one additional generation by allowing the F1 fish to mature in the hatchery, artificially spawning them there, and stocking their progeny with the candidate life stages being the same as for F1 releases (eggs, fry etc.).
Fry: A salmon in its first year of life.
Live Gene Banking: A program in which the genetic diversities of severely depleted wild salmon populations are maintained in a hatchery (often referred to as a biodiversity facility) setting.
Parr: A juvenile salmon occupying the freshwater environment and is 1 year old or older.
Precautionary Approach, a system that is currently being implemented on New Brunswick salmon rivers and categorizes wild salmon populations into three zones based on estimated population levels. These zones are:
- Critical Zone: The spawning population in this zone is below the level which it will produce a juvenile population that will result in one half of the maximum smolt run for the river in question. For example, on the Northwest Miramichi, at an egg deposition of 1.74 per m2 of habitat, there is a high likelihood that one half the maximum smolt run from that spawning cohort will be achieved. At egg depositions below this value, the population is in the Critical Zone, and no unnecessary removals or harvests are recommended. The 1.74 eggs per m2 value is termed the Limit Reference Point (LRP). The LRP is specific to each individual river.
- Cautious Zone: In this zone, the population has achieved and exceeded the Limit Reference Point but is less than the Upper Stock Reference (USR), which is usually two to three times the Limit Reference Point. For example, if the USR were defined as being 2.5 times the Limit Reference Point of 1.74, the Cautious Zone would be 4.35 eggs per m2. Within this zone, harvest and removals can increase with increasing egg deposition values that are achieved until a maximum harvest/removal level is reached at the Upper Stock Reference (USR).
- The Healthy Zone. In this zone, egg deposition has exceeded the Upper Stock Reference, and a flat maximum harvest rate is recommended no matter how far egg deposition exceeds the USR.
Rehabilitation: Fish stocking is used, in conjunction with any requisite changes to harvest strategies and other appropriate management strategies, to help preserve a locally or regionally depressed wild, native fish population and facilitate a return to a self-sustaining state.
Smolt: A juvenile salmon that is physiologically capable of living in full-strength sea water. Wild smolts are normally actively migrating from freshwater into salt water. When they have entered salt water, they are considered post-smolts.
Smolt-to-Adult-Supplementation (SAS) Program (Also known as a Captive Adult Rearing Program): A program in which wild smolts are captured and raised in the hatchery to maturity. The adult fish can then be released to spawn naturally as F0s or spawned in the hatchery with (usually) the F1 fry being released. Stocking: the introduction of fish produced or reared in captivity into natural fish habitat. Strain: a group of individuals with common ancestry that exhibits genetic, behavioral, physiological, or morphological differences from other groups of the same species. Wild Atlantic Salmon: Any salmon above an F0. Atlantic salmon are considered “wild” if they were spawned in the wild and are from wild parents. In the case of Live Gene Banking, salmon that are the progeny (smolts or large parr) of wild parents and are reared in captivity from juveniles to maturity and then released are wild fish as are their progeny. Fish that are hatched in captivity and released to the wild are not.
Types of Stocking
Based on the objectives and expected impacts, acceptable types of stocking could include:
Type 1 (traditional) stocking attempts to address juvenile production limitations in the freshwater environment by taking adult salmon (usually wild adults), spawning them artificially and producing various juvenile stages in hatcheries or other satellite facilities. The juveniles are then released to the wild where they grow to adulthood and spawn and/or provide fisheries benefits. Although juvenile stages, such as fertilized eggs, fry, fall fingerlings and fall yearlings, can be produced and released, the ultimate Type 1 products are smolts for which juvenile exposure to natural freshwater environments is eliminated. In the past, this was done at the Mactaquac Hatchery on the St. John River. The Mactaquac Type 1 stocking program “sea ranched” smolts, the intent being to compensate for freshwater habitat loss due to the construction of the Mactaquac Dam and Generating Station. Another example of a Type 1 program is streamside incubation.
Because Type 1 programs usually involve removing wild adults thereby exchanging wild spawning with artificial spawning and juvenile rearing, caution should be employed. Efforts must be taken to maximize the genetic diversity of the progeny produced. However, these programs can have some benefit in reducing egg mortality due to wild-spawning inefficiencies or incubation problems (i.e. egg and fry mortality due to fungus, poor nest irrigation, sedimentation, temperature fluctuations etc.).
Type 2 stocking, or captive-adult rearing or reconditioning (i.e., Kelt reconditioning) attempts to address excess mortality of post-smolts and kelts in the marine environment by producing adults from wild juveniles or reconditioned wild spawners. In most cases wild smolts are captured and then raised to maturity in captivity, with the mature fish then released to spawn naturally (an F0 stocking project). Alternatively, the wild juveniles are held to maturity in the hatchery, and spawned there to produce F1 juvenile fish, often unfed fry for stocking. Great numbers of fish for rapid rehabilitation can be produced if large numbers of these juvenile fish are themselves held to maturity and allowed to spawn in the wild or are spawned in the hatchery to produce F2 fry. Complete F1 or F2 programs that release unfed fry rather than mature adults reduce the theoretical risk of genetic dilution of wild strains by avoiding spawning between wild and hatchery-held fish.
When a population’s egg deposition is trending towards the Critical Zone (see Precautionary Approach above), rehabilitation programs using Type 2 stocking could be considered including:
A. When egg deposition is approaching the level at which the depressed population phenomenon is likely, a Type 2 / F1 adult release or Type 2 / F2 stocking program should be considered and is almost mandatory.
B. When the egg deposition average is chronically below the Limit Reference Point, a Type 2 / F0 adult release or Type 2 / F1 stocking program should be considered.
- All stocking efforts. A well-defined trigger for stocking should be agreed upon. Because a program started from scratch takes several years to implement, there is a danger that it may be initiated too late. NBSC suggests that when the six-year1 moving average trend level in egg deposition falls below an agreed upon ratio of the LRP (e.g., 90%), a stocking program be prepared. If a catastrophic single year occurs (e.g., 50% of the LRP) a program should be planned and ramped up immediately.
- Where possible, stock only Atlantic salmon that are of wild origin, native to the specific water body genetically appropriate, and certified disease-free. Non-wild salmon can be stocked, but preference should be given to maximizing the wild exposure of the stocked fish. For example, unfed fry > feeding fry> fall fingerlings> yearlings> smolts. When it is not possible to use a source endemic to the watershed being stocked, use genetically similar fish sourced from neighboring watersheds/ecosystems.
- A stocking program should be conducted in conjunction with programs to address the root causes of the stock’s decline.
- Ensure a broad review of the potential benefits and impacts of stocking is conducted and taken into consideration.
- Demonstrate that the removal of juvenile or adult salmon from the wild to enhance future egg deposition in natural habitats clearly benefits stocks.
- All fish to be stocked must meet Department of Fisheries and Oceans’ health requirements per the Fish Health Protection Regulations and the Fishery (General) Regulations.
The following should be implemented prior to initiating fish-stocking projects:
- Identification of the root causes of the population weakness.
- A clear description of the objectives of the project and quantifiable measures to evaluate its success.
- A review of the ecological, economic, and social impacts of the project.
- A determination that stocking is the most appropriate interim management strategy.
- A determination of the appropriate strain, age class and stocking rate based on the intended stocking objective.
- Proper permitting from the New Brunswick Introduction and Transfers Committee. · Devising an exit strategy – i.e., schedule or criteria for when stocking is no longer required.
- If the problems causing the need to stock cannot be resolved (e.g., effects of generationally permanent power dams or habitat loss to urbanization) mitigation of these effects through stocking should continue in perpetuity.
Evaluation, monitoring, and re-assessment
Follow-up monitoring of Atlantic salmon stocking programs should be done to determine the success of stocking efforts according to the quantitative measures of success established for each stocking initiative. This monitoring could include fish population estimates and angling/harvest surveys to assess population recovery and/or stocked fish growth and return rates as indicators of stocking success.
To help ensure stocked fish can be easily distinguished once released among wild fish, each should be given, where possible, a mark prior to stocking.