Atlantic menhaden

A benchmark assessment was conducted in 2015 (SEDAR, 2015) by the Atlantic States Marine Fisheries Commision.  Results indicate a robust stock. The model in use is a sophistication on previous assessments, but incorporates many changes which are thought to improve precision. The problematic retrospective pattern found in the last update has been resolved (SEDAR, 2015). This assessment has moved away from a time varying natural mortality, which may hamper projection precision should the predator demand change. There are uncertainties with respect to bait landings and reporting.

An update of the existing model was conducted in early 2017. This model used revised historical catches that only changed the total removals slightly, and re-scaled the catchability of the northern index, one of two fishery independent indices that measure the population. The results of this updated model changed the size of the population, and the numerical value of the fishing and fecundity reference points (ASMFC 2017; McNamee, J 2017). Due to the afore mentioned change in catchability of the northern index, the population model revised the overall fecundity downward when compared to the benchmark, however fecundity reference points also were revised downward resulting in no change in stock status.

Atlantic menhaden is in the process of a benchmark assessment; results are expected at the end of 2019.

In the past the Technical Committee, which provides scientific advice to the management process, recommended the development of more conservative single species reference points based on management goals, aiming to end overfishing and to provide increased protection to population spawning biomass. The benchmark in 2015 as well as previous ones suggested that ecosystem-based reference points be adopted. Additional recommendations by the assessment team, which completes the assessment and determines stock status relative to reference points, were to increase data collection and to improve the assessment methodology, in order to reduce uncertainty in the estimates (SEDAR, 2015). A full benchmark is scheduled for 2019 which will examine reference points that account for predation. 

As of the most current updated assessment (ASMFC 2017)(McNamee, J 2017) stock biomass/fecundity is slightly below (~15%) its fecundity target while fishing mortality is well below threshold levels. 

Overall landings had been in decline since 1990. But the bait landings have been variable but slightly increasing over the most recent time period since 2005.  Fecundity has been highly variable, but in 2006 jumped to a new higher plateau and while still variable, has hovered at a higher level than previously. Fishing mortality has been in decline since the later 1990's, and was at its lowest point historically in 2013 (SEDAR, 2015). Fishing mortality has increased slightly each year since 2013 (ASMFC 2017)(McNamee, J 2017).

In December 2012,  management measures were approved under Amendment 2 of the FMP (Fishery Management Plan), in order to stop what was then overfishing from occurring. Conservative biomass reference points were adopted at the time, aimed at being consistent with the recently implemented fishing mortality reference points (RP), and intended to be interim RP while ecological-based reference points (ERP) are developed in 2019. These interim RP were then updated during the update assessment in 2017 (ASMFC 2017)(McNamee, J 2017).

F_Target = 0.80; set at a level corresponding to 36% of Maximum Spawning Potential (MSP)
F_Threshold = 1.85; set at a level corresponding to 21% MSP

Fecundity Target (Spawning Stock Biomass (SSB) target or SSB_36%MSP) = 99.5 × 10¹² eggs
Fecundity Threshold (SSB_Threshold or SSB_21%MSP) = 57 × 10¹² eggs 

Quotas have also been increased; both in 2015 and 2018. Quotas for 2018 have again increased from 198,000 t to 216,000 t (ASMFC 2017). However bycatch landings (<6,000 pounds per trip aproximately 2,686 t per year total) are not counted against this quota (ASMFC 2018).

Other management measures include: i) a coast-wide TAC of ~214,000 tonnes for 2018, which was then split up state-by-state; ii) A Chesapeake Bay reduction fishery harvest cap (new annual cap is now 98,192 tonnes for 2018), with additional specifications on the rollover of unlanded fish between years(ASMFC 2016)(ASMFC 2017) and iii) requirements for timely reporting of catch and compliance with regulations (ASMFC, 2012c) (ASMFC 2016)(MFC 2017) 

This fishery is closely monitored. Compliance with reporting and the Chesapeake Bay harvest cap is very high. In 2017 total reduction harvest from the Chesapeake Bay was less than 20,000 t, well below the 51,000 t cap (ASMFC 2018).

Gear restrictions and closed seasons and areas in the menhaden bait fishery are easily enforced. Compliance in states where this harvest is permitted is deemed very high for area/seasonal closures and gear restrictions. However there is some uncertainty on reporting and removals by the bait fishery due to state by state differences in regulations. Coast wide harvest was below the quotas set by ASMFC in 2016 and 2017 including the bait fishery. However menhaden landed as part of the bycatch fishery, while reported, are not counted against the quota (ASMFC 2018)

Overall the purse seine fishery has some interactions with protected marine species, including birds, mammals and fish (ASMFC, 2012c). These include minke whale, humpback whale, bottlenose, Atlantic-white sided dolphin, harbor seal, grey seal, Harp seal, and harbor porpoise. Interactions are minimal however (NOAA 2018) as the fishery is listed as a Category II fishery with only occasional interactions. Harvesters are required under Category II to report interactions, as well as carry at-sea observers if requested.

Additionally, National Marine Fisheries Service (NMFS) and ASMFC have implemented a number of mitigation factors in the event that this or other fisheries are found to interact with marine mammals in deleterious way. This includes implementing a take reduction team (TRT), which can implement time area closures, gear restrictions and other measures if the menhaden purse seine fishery is found to have increased interactions with protected marine mammals, turtles, and seabird species. To date however interactions have not been a cause of concern (ASMFC 2017).

An observer program was recently required in the purse seine fishery to better evaluate interactions with sea turtles (NOAA, 2012b) but data has not been made public due to data confidentiality. It is expected that such findings will become apparent during the ongoing MSC certification process.

The bycatch in the Atlantic menhaden fishery is considered very low (ASMFC, 2012c). For example, Austin et al., (1994) found that bycatch of fish in the 1992 reduction fishery comprised approximately 0.04% by number. Other studies suggest, bycatch of other species is of less than 0.1% by weight (NOAA, 2012a). 

Overall however this data is rather dated and only for the large industrial purse seine fishery. An observer program was recently required in the purse seine fishery to better evaluate interactions with sea turtles (NOAA, 2012b) but data has not been made public due to data confidentiality. It is expected that such findings will become apparent during the ongoing MSC certification process. Other fisheries using purse seine gear but targeting other small pelagics (Atlantic herring) have minimal bycatch associated with them (NMFS 2015). However the bycatch data in the growing small purse seine fisheries which targets menhaden is not well known. This small fishery only comprises 20-30% of the landings however (ASMFC 2018).

Atlantic menhaden is mainly caught by purse seines, which is a gear that operates in the water column. Although contact with the bottom may occasionally occur in purse seine fisheries, particularly in shallow waters, physical and biological impact on sea floor is usually low (Chuenpagdee et al., 2003; NOAA, 2012a).

Nearly all estuarine and coastal waters from Nova Scotia to Florida are important habitat for juvenile and adult Atlantic menhaden. Adults are found mainly in coastal ocean waters while juveniles are found in estuarine waters. Most of the menhaden fishery is focused in ocean waters or large estuaries. There is little to no impact from menhaden fishing to habitat in these areas (ASMFC 2011b).  

Despite this States have an obligation to restrict purse seine activities, including the fishery for menhaden, should habitat impacts be found (amend 3). Some state have in fact done so, by elimination of purse seine in state waters or by limiting the gear/season of operation, out of an abundance of precaution (ASMFC 2018).

Ecosystem

Information and analysis of menhaden as a forage species is currently underway. During the most recent benchmark assessment (SEDAR 2015) efforts were made to quantify the impact of menhaden removals on other predators in the region. Data included in that analysis ranged from specific food habits information for major predators, as well as back ground environmental information which could affect recruitment. Guidance from the peer review focused attention on medium scope modeling approaches to move forward.

Based on this, managers first instituted a workshop to define ecosystem reference points goals and objectives (ASMFC 2015), and then formed a Biological and Ecological Reference Points workgroup (BERP). The task of this group was to work side by side with the assessment team during the 2019 benchmark process to produce reference points to explicitly address menhaden’s role as forage in the ecosystem. This work is ongoing.

In the interim, mangers adopted precautionary reference points and low quotas specifically to address the uncertainty surround menhadens role as forage, and potential removal by commercially and recreationally important species (ASMFC 2017)(ASMFC 2018).