Saturday, October 19, 2013

Climate Change, Phenology and Niche

One of the fundamental questions that ecologist ask is "what are the physical conditions that enable species co-existence?" or alternatively "what are the physical conditions that enable species dominance?" Ecologist often use the fundamental niche to describe conditions that a species is suited, and the realized niche to describe the locations  (or conditions) where the species is actually observed.

Rapidly changing temperatures are causing a bit of a stir. Many plants and animals life-histories are tightly controlled or coupled with environmental conditions. For instance,  you may have noticed that years with warmer springs often bring earlier blossoming of cherry trees. Not all plants and animals respond to higher temperatures in the same way, some species' phenology (or timing of a life history event) may be tightly coupled with temperature while others less so. Large scale variation in temperatures can thus alter the relative timing of phenology between two species. If one of these species is dependent on the other for food this can be a bad thing for species B. Climate change can not only influence the relationship between predator and prey it can also change the amount of apparent competition between sets of species.

In a paper I have recently published, I showed that higher temperature can lead to less niche overlap between species in the southern New England benthic community, specifically the "fouling community". The fouling community is compose of animals like tunicates, mussels, barnacles and bryozoans that compete for space on hard substrates like subtidal boulders. Niche overlap has been used as a proxy for competition between species within a community. Lower niche overlap may be a result of earlier recruitment driven by temperature. Higher temperatures effectively make more time available for species in the community to recruit. With more time available for recruitment this may mean that there is less competition for some species during there periods of recruitment.

One interesting pattern that we observed during this study is that more recent invasive species tend to recruit latter in the year. Another way to way this is that the the timing of recruitment of invasive species is correlated to there relative time of there historical invasion into southern New England. The reasons for this pattern are not quite clear but this may be a case of species evolving earlier recruitment.

Thursday, January 10, 2013

Atlantic Bluefin Tuna, Amendment 7, and the Future of the Northwest Atlantic Purse Seine Fishery

In 2013 NOAA, through the Atlantic Highly Migratory Species Division, will likely re-allocate bluefin tuna fishing quotas for all allowable fishing methods, known as gear types. NOAA has categorized the redistribution of allocation among gear types as a “first tier” priority in the Amendment 7 scoping documents (NOAA 2012a). This amendment has potentially important and long-lasting implications to the bluefin tuna fishing sector. Redistribution could virtually eliminate the quota allocation for purse seine fishery. Such a drastic change to the “quota landscape” deserves close scrutiny to understand the cause and consequences of the change.

Atlantic bluefin tuna (Thunnus thynnus) are among the most highly prized fish in the ocean with the result that persistent overfishing has significantly diminished populations. Since the 1990s bluefin tuna has been listed as endangered on the IUCN red list (Collete et al 2012) and as a species of concern under the U.S. Endangered Species Act. (A review of the latter designation will take place in 2013, possibly placing the species in the endangered or threatened category.)

In 2012, NOAA Fisheries (the domestic regulatory agency that manages Highly Migratory Species [HMS]) began the process of drafting Amendment 7 to the 2006 Consolidated Atlantic Highly Migratory Species Fishery Management Plan (Federal Register 2012). Amendment 7 will provide the framework for managing Atlantic bluefin tuna consistent with the legal mandates provided in the Magnuson-Stevens Act and Atlantic Tunas Convention Act for the foreseeable future. These mandates include ending overfishing and re-building stocks to ensure that populations return to healthy levels. The amendment provides the opportunity for enhanced reporting of catches, changes in the minimum retention size, designation of new temporal or spatial closures, as well as quota requirements that define, by gear and license types, the Atlantic fleet’s total allowable catch poundage. Amendment 7’s regulations will be crucial for the sustainable management of Atlantic bluefin and the conservation of the species.

Current Quota Allocations
Amendment 7 will likely address the quota allocations among different gear types.  The current distribution, based on catches from 1983 to 1991,
breaks down as follows:

             General – 47.1%
             Angling – 19.7%
             Purse seine – 18.6%
             Longline – 8.1%
             Harpoon – 3.9%
             Trap – 0.1%
             Quota overages from previous categories– 2.5%

NOAA Fisheries has two main reasons for changing
the current allocation system:
1)   The system does not accurately reflect the current distribution of fishing landings (fish catch brought to shore for sale). In particular, there has been a substantial increase in recreational catches (made by individuals rather than commercial operations) and a dramatic decline in purse seine category catches.
2)   The current allocation does not account for dead discards, fish that fail to meet minimum size requirements or other criteria that prevent them from being kept. Released dead fish can dramatically reduce the potential profits of a fishing operation, a fact that is not fully accounted for by the current fish-landing allocation system. Recent science and data analyses have shown that dead discards can represent a significant proportion of stock biomass.

Why Amendment 7 Is Likely to Affect Purse Seining More Than Other Methods
Purse seining,  a style of fishing that uses nets to encircle a school of fish, began in earnest in the Northwest Atlantic after World War II with a single seiner off the coast of New England. Gradually, more vessels joined the fleet, and the fishery reached its maximum catch in 1963 and maximum number of participating vessels in 1964.  However, as purse seiners became more proficient and as new technologies became standard (e.g., using airplanes to spot schools of fish), capacity began to exceed fishing yield (Sakagawa 1975). Since 2006, landings have fallen well short of allocation. In three of the past six years there have been no purse seine landings at all.  With profits eroding, only five vessels, home ported in Gloucester and New Bedford, Massachusetts, continue to use this method (NMFS 2006). In addition, NOAA no longer issues purse seine fishing permits, and regulations prohibit the transfer of permits.

The failure of purse seining is largely related to fish harvesting and sale size restrictions imposed by NOAA.  In general, purse seiners have to catch “giants,” larger than 80 inches in length (but are allowed a small amount of fish under this size). With purse seining, the relative size fraction of a school of fish cannot be discovered without significant effort and the risk of little return for that effort. The purse seine fishery was developed for catching fish for canneries (i.e., for canned tuna). Canneries prefer a smaller fish than the high-value Japanese sushi market.

In 2004 and 2005, as “giants” became scarce, purse seiners also had to contend with a precipitous price drop for bluefin tuna from a high in the late 1990s of approximately $9/lbs to $2.18/lbs in 2005. As a result, purse seine fishing no longer made financial sense. Simultaneously, New England sea scallop fishery was becoming the most valuable US fishery, drawing interest away from bluefin tuna.
Without the return of bluefin tuna schools with “giants,” the purse seine fishery has been quiet; and since 2006 the quota allocated (18.6%) to the purse seine fishery has been a defacto reserve for the rest of the fishery, essentially serving to cover overages and accounting for dead discards by other gear types. While some have suggested that relaxing minimum sizes requirements might revitalize thecategory, this change is unlikely because of NOAA’s commitment to protect smaller fish to allow them to reach maturity and spawn.
Alteration of size minimums and purse seine catch tolerances has already been relegated to secondary status in Amendment 7 scoping. Purse seiners may have to wait until Atlantic bluefin schools have matured before returning to profitability. Predicting when - and if - this utilization of quota will occur is a management issue.

Options for Reallocating Bluefin Tuna Quotas
The scoping documents of Amendment 7 outline three general approaches to
quota reallocation:
A)   Revise quota allocations based on current catch and historic allocation
B)   Revise quota
allocations based on historic allocation discounted by a fraction to account for dead discards
within each gear type
C)   Redistribute quota from gear types that have not met allocation (in recent years) to categories that have insufficient quota to cover (NOAA 2012a).

Option A. When recent catch is considered most heavily, the purse seine fishery all but vanishes. Categories that lose quota are the harpoon and general categories. The excess quota “gained” from the “losers” is transferred to the angler (recreational) and the longline categories, the new quota would be used to account for their dead discards while leaving there landings at current levels. Using this option, the defacto quota reserve of the purse seine fishery becomes official reserve for the longline and the angler categories. The more weight given to recent catch, the larger the reserve.
Option B. This option draws quota from each category, thereby creating additional reserves. For example, each category may experience a 10% cut. Gear categories that are particularly unselective an   discards, such as longline, couldreceive greater cuts than other categories. In this option, purse seiners would maintain a substantial amount of their quota, leaving each of the remaining categories to account for their dead discards. This option has the potential to provide additional defacto reserve, but leaves fishery managers with the uncertainty of hen, and if, purse seiners will return to fish.
Option C. This option disproportionately affects purse seiners as it redistributes quota from their fishery to the longline fishery to cover dead discards. Again, this option essentially eliminates the defacto reserves that the purse seine category has provided over the last six years.
As NOAA Fisheries continues to refine the Amendment 7 draft, it will need sound and reasoned input from citizens concerned with our natural resources and, in particular, the bluefin tuna fishery. People will have the opportunity to comment on the proposed amendment before it becomes regulation. Ultimately, the fate of the purse seine fishery will have important implications for at least the next 10 years of bluefin tuna management.

Threatened Species. Version 2012.2. . Downloaded on 29 October 2012.
Federal Register (2012) Vol. 77, No. 78
NMFS. (2006) Final Consolidated Atlantic Highly Migratory Species Fishery Management Plan. National Oceanic and Atmospheric Administration, National Marine Fisheries Service, Office of Sustainable Fisheries, Highly Migratory Species Management Division, Silver Spring, MD. Public Document. pp.

NOAA (2012a) National Oceanic and Atmospheric Administration, National Marine Fisheries Service, Office of Sustainable Fisheries, Highly Migratory Species Division NOAA (2012b)  National Oceanic and Atmospheric Administration, National Marine Fisheries Service, Office of Sustainable Fisheries, Highly Migratory Species Division

Sakagawa GT (1975) The purse seine fishery for bluefin tuna in the Northwestern Atlantic ocean. Marine Fisheries Review 37:1-8