INTERNATIONAL COMMISSION FOR THE CONSERVATION OF ATLANTIC TUNAS (ICCAT)

Transcription

1 INTERNATIONAL COMMISSION FOR THE CONSERVATION OF ATLANTIC TUNAS (ICCAT) 1 INTERNATIONAL COMMISSION FOR THE CONSERVATION OF ATLANTIC TUNAS (ICCAT) Description of national level detailed assessment of the state of fish stocks The International Commission for the Conservation of Atlantic Tunas (ICCAT) is responsible for the study of the populations of tuna and tuna-like fishes and other species of fishes, primarily Yellowfin tuna, Bigeye tuna, Skipjack, Albacore, Atlantic Bluefin, Southern Bluefin (which falls under the ICCAT mandate for the Atlantic but is managed by CCSBT), Mediterranean Swordfish, sailfish, blue and white marlin, Spanish and king mackerel, small tunas such as black Skipjack, frigate tuna, and Atlantic bonito, and pelagic sharks exploited in tuna fishing in the Convention area that are not currently under the jurisdiction of other international fishery organizations. ICCAT conducts studies which include research on the abundance, biometry and ecology of the fishes, the oceanography of their environment, and the effects of natural and human factors upon their abundance. ICCAT maintains the ability to utilize the technical and scientific services of, and information from, official agencies of the Contracting Parties and their political sub-divisions and may utilize the available services and information of any public or private institution, organization or individual, and may undertake, within the limits of its budget, independent research to supplement the research work being done by governments, national institutions or other international organizations. ICCAT s goal is to maintain the populations of tuna and tuna like species at levels which will permit the maximum sustainable catch for food and other purposes as stated in the Preamble to the ICCAT Convention. The status of some of the target species governed by ICCAT can be found in a recent report. 1 Yellowfin tuna Yellowfin tuna is distributed mainly in the tropical and subtropical oceanic waters of the Atlantic, Pacific and Indian oceans. Juveniles form mixed schools with skipjack and juvenile bigeye, mostly in surface waters, while larger fish form schools in surface and sub-surface waters. Spawning occurs in the equatorial zone of the Gulf of Guinea, in the Gulf of Mexico, in the southeastern Caribbean Sea, and off Cape Verde, but the relative importance of these spawning grounds is unknown. Although such separate spawning areas might imply separate stocks or substantial heterogeneity in the distribution of yellowfin tuna, a single stock for the entire Atlantic is assumed as 1

2 2 INTERNATIONAL COMMISSION FOR THE CONSERVATION OF ATLANTIC TUNAS (ICCAT) a working hypothesis, based in part on a 40-year time series of longline catch data that indicates yellowfin are distributed continuously throughout the entire tropical Atlantic Ocean. The most recent full assessment was conducted in 2003 applying various agestructured and production modelsto the available catch data through These analyses implied that although the 2001 catches were slightly higher than MSY, effective effort may have been either slightly below or above (up to 46%) that necessary to achieve MSY, depending on the assumptions. Catches have been in decline since the last assessment, they are lower than MSY and some surface fishing effort has transferred to other oceans. Catches have declined by more than half from close to tonnes in 1990 to tonnes in 2006 partly due to a reduction in eastern Atlantic purse seine effort, but other factors have caused the reduction of baitboat and purse seine catches in the western Atlantic, as well as the more recent declines of longline catches in both the western and eastern Atlantic. It may be difficult to assess whether catch declines are due to stock declines, to reduced effort or other factors. In 1993, the Commission recommended that there be no increase in effective fishing effort exerted on Atlantic yellowfin tuna, over that observed in As measured by fishing mortality estimates from the 2003 assessment, effective effort in 2001 appeared to be approaching or exceeding that of Catches have been declining since 2001, as has the nominal effort of the purse seiners, but the trend in effective effort is not clear. Yellowfin tuna appear to have been harvested in the vicinity of MSY in the late 1990s and the early 2000s, but catches and effort have declined since. It is not known if the productivity of the resource has decreased, implying that MSY would now be lower, or if the fish have become less available. It would be prudent to assume that the productivity has in fact declined until it can be demonstrated that this is not the case. Bigeye tuna MSY estimate not available. Although in 1990 Bigeye tuna stocks declined rapidly, stocks have been stabilized recently. However, there is a lack of information regarding detailed fishing and size data from certain fleets, in addition to past catch and fishing activities of IUU fleets. If major countries were to take their entire catch limits and other countries were to maintain their recent catch levels, total catch would then exceed 100,000 tons, well above the total catch of tonnes that the Committee recommends for rebuilding efforts. There is no rebuilding plan in place. Bigeye tuna are distributed throughout the Atlantic Ocean between 50ºN and 45ºS, but not in the Mediterranean Sea. Spawning takes place in tropical waters when the environment is favourable. From nursery areas in tropical waters, juvenile fish tend to diffuse into temperate waters as they grow larger. Catch information from surface gears indicate that the Gulf of Guinea is a major nursery ground. Available evidence suggests an Atlantic-wide single stock. Bigeye tuna is exploited mostly by longline, baitboat and purse seine used by many countries throughout its range of distribution. The total annual catch increased relatively steadily to more than 132,000 tonnes in 1994 before decreasing for all major gears to

3 INTERNATIONAL COMMISSION FOR THE CONSERVATION OF ATLANTIC TUNAS (ICCAT) 3 76,000 tonnes in Decreased catches are due to reductions in fleet size for purse seine and longline and lower CPUE for longline and baitboat. The 2007 stock assessment examined production models, VPA, and a statistical integrated model. Information is still lacking on size data from certain fleets, including IUU fleets which makes it necessary to assume catch-at size for an important part of the overall catch. The results from non-equilibrium production models are considered to best characterize the status of the resource. Current MSY is estimated to be approximately tonnes, reflecting the existing mix of fisheries that capture small or large bigeye. MSY estimates can change considerably with changes in the relative fishing effort exerted by surface and longline fisheries. The biomass at the beginning of 2006 was estimated to be nearly 92% of BMSY and the 2005 fishing mortality rate was estimated to be about 13% below FMSY. Skipjack tuna MSY estimate not available. The increased use of fish aggregation devices (FADS) and the increase of the fishing area towards the west since the early 1990s have led to an increase in Skipjack catchability and the proportion of Skipjack stock that is exploited. Estimates of catches made in 2007 indicate a 10% increase from the average of Traditional stock assessment is difficult to apply to Skipjack tuna because of their particular biological and fishery characteristics; several assessment methods were used to assess stocks and several fishery indicators were analyzed; separate assessments were made for eastern and western stocks. There is no rebuildling plan in place. Skipjack tuna is the predominant species under fish aggregating devices (FADs) where it is caught in association with juvenile yellowfin tuna, bigeye tuna and with other species of epipelagic fauna. It spawns from its first year of life opportunistically throughout the year and in vast sectors of the oceans. Skipjack tuna is considered resilient to exploitation. Total catches increased steadily from less than tonnes in the early 1960s to more than tonnes in Catches have since declined to about tonnes in Numerous changes in the skipjack fishery since the early 1990s (such as the use of FADs and the expansion of the fishing area towards the west) have caused an increase in skipjack catchability and in the proportion of the skipjack stock that is exploited. according to a tag-recovery model on fish measuring cm FL. Estimates of Z based on the annual average size of the catches suggests a smaller increase and even a decrease after Atlantic skipjack have not been assessed since 1999 although there are some signs of local overexploitation. No standardized assessment of the Atlantic skipjack stocks can be carried out, but the development of several fishery indicators are believed to reflect the changes in the state of the stock over time. Although the fisheries operating in the east are extending towards the west beyond 30 o W longitude, the hypothesis of two distinct stock units continues to be used. However, given the biological characteristics of the species and the geographic distances between the various fishing areas, using smaller stock units could be investigated.

4 4 INTERNATIONAL COMMISSION FOR THE CONSERVATION OF ATLANTIC TUNAS (ICCAT) Albacore tuna In northern stocks of Albacore, which are exploited by surface fisheries targeting immature and sub-adult fish, longline fisheries target immature and adult Albacore. Recent catch rates have showed declines; decreases in longline fisheries are mostly due to decrease in landings by Chinese Tai Pei fleet and a decrease of Albacore as by-catch by the Japanese. Based on the 2007 assessment which considers catch, size and effort since the 1930s, the spawning stock biomass (SSB) has declined and is currently about one quarter of the peak estimated for the late 1940s. TAC for northern Albacore stock was 34, 500 tons until 2007, and the Committee noted that reported catches for 2005 and 2006 were over TAC. Stock projections indicate that the northern stock will not recover from overfished conditions if catch levels remain over tonnes. Recent catches for southern stocks have been below TAC level. Although assessments show that stocks are overfished currently, model projections indicate that should catch levels remain at the 2006 level, stocks will recover to MSY levels. There is no rebuilding plan in place. Estimates of recruitment to the fishery, although variable, have generally been higher in the 1960s and earlier periods with a declining trend thereafter. The most recent recruitment is estimated to be large but it is uncertain. The stock appears to have rebuilt to near B MSY. Recent fishing mortality rates have generally been above F MSY (current F is approximately 50% larger than F MSY ). Yearly estimates of MSY varied depending on the relative combination of fisheries taking juvenile and mature albacore. The South Atlantic albacore fishery has been dominated by the surface baitboat fleets from South Africa and Namibia, and the longline fleets from Brazil and Chinese Taipei. The surface fleets direct for albacore and mainly catch juvenile and sub-adult fish (70-90 cm FL). Total reported albacore landings for have fluctuated between tonnes and 40,000 tonnes for the last 20 years without clear trend. In the South Atlantic, based on the 2007 assessment which considers catch, size and effort since the 1950s, the Southern albacore spawning stock has declined to about 25% of the unfished SSB. It is likely that the stock is currently below MSY while the 2005 fishing mortality rate was about 60% of F MSY. MSY was estimated to be around tonnes. There are insufficient data to assess albacore in the Mediterranean; it is recommended that that more information be collected for Mediterranean albacore so that an assessment be conducted at the earliest possible date. In 2007, a TAC reduction was advised for the North Atlantic stock and no change for the South Atlantic stock. SSB is estimated to be smaller than the SSB at MSY for both the northern and the southern stock. Fishing mortality is estimated to be above F MSY in the northern stock but less than F MSY in the southern stock. Atlantic Bluefin tuna With regard to Atlantic Bluefin a lack of compliance with the TAC and underreporting of catches by fishing vessels undermine efforts to conserve stock. Exports to Japanese and US markets greatly exceed the reported catches. Poor temporal and spatial coverage coupled with substantial underreporting of total catches hinder efforts to accurately assess the state of stocks. The committee s results from the most recent assessment made in 2006 indicate that spawning stock biomass has been declining rapidly in the last several years, while fishing mortality has been increasing rapidly. Fishing mortality is most likely 3 times that which would result in MSY and biomass 36% less

5 INTERNATIONAL COMMISSION FOR THE CONSERVATION OF ATLANTIC TUNAS (ICCAT) 5 than the level needed to support MSY. Substantial overfishing is occurring and spawning biomass is well below the levels needed to sustain MSY. There is no rebuilding plan in place. ICCAT has two management units for bluefin tuna, the West Atlantic and the East Atlantic plus Mediterranean. Recent stock assessments have been conducted under a two stock hypothesis, but the 2008 assessment also considered a preliminary single stock hypothesis assessment for exploratory purposes. Catches now come from considerably smaller area than in the 1960s, including the disappearance of fisheries off Brazil and off Norway; catches in the West are now much smaller than in the 1960s; fisheries have expanded in the middle of the Atlantic north to Iceland; and purse seine catches have been eliminated in the West but have increased considerably in the Mediterranean, particularly in the eastern Mediterranean where there were few catches in the 1960s. Since the imposition of TACs in 1981, the total catch for the West Atlantic including discards has stabilized between about tonnes and tonnes. The SCRS was particularly concerned that the TAC has been seriously under caught in recent years. In the East Atlantic, reported catches increased from the early 1980s to the late 1990s and have been generally declining since. In the Mediterranean, reported catches were generally less than tonnes from 1950 to 1980, increased steeply to tonnes in the mid 1990s, decreased abruptly from 1996 to 1999 and have generally remained above tonnes since. The introduction of farming activities into the Mediterranean in 1997 and good market conditions resulted in rapid increases in fishing effort in the Mediterranean fisheries for bluefin tuna. Reported catches in recent years are believed to be considerably smaller than actual catches. For the West Atlantic, the 2006 assessment suggests that SSB declined rapidly in the early 1970s followed by a more gradual decline with the 2004 SSB being about 19% of the 1975 SSB. While it is clear that current biomasses are considerably smaller than those of the early 1970s, year classes since the mid 1970s have not been large enough to rebuild the stock. If small year classes since the mid-1970s are due to low spawning stock, then rebuilding the SSB should lead to progressively larger year classes and it would be possible to rebuild the stock. For the eastern Atlantic and Mediterranean, the 2006 assessment suggested that the biomass declined by approximately half from the early 1970s to the mid-1980s, subsequently increased until the early 1990s and has been decreasing since to the lowest observed in the time series (Figure BFT 5). Fishing mortality, particularly on older and larger bluefin, is estimated to have increased sharply and be about 3 times FMSY. This increase in fishing mortality estimated for large bluefin is consistent with a shift in targeting towards larger individuals destined for fattening/farming. The SCRS believes that the TAC regulation have been largely ineffective in controlling overall catch with actual catches believed to be tonnes to tonnes higher than reported. It also believes that the 15-year recovery plan for East Atlantic and Mediterranean bluefin is a step in the right direction, but that it is unlikely to rebuild to BMSY in 15 years with 50% probability.classes are due to causes other than low spawning stock, e.g. changed environmental conditions, loss of spawning habitats, or losses of spawning components, then, it may not be possible to rebuild the stock to the high biomasses estimated for the 1970s and earlier unless catches are reduced to near zero.

6 6 INTERNATIONAL COMMISSION FOR THE CONSERVATION OF ATLANTIC TUNAS (ICCAT) Southern Bluefin Tuna There has been no assessment of Southern Bluefin stock by ICCAT; a separate assessment was done by Commission for the Conservation of Southern Bluefin Tuna (CCSBT). Atlantic Swordfish According to the last assessment made in 2006, Atlantic Swordfish stocks were in good condition, on track to achieving MSY. However, higher catches of southern stocks as currently envisioned by the Commission may not be sustainable, from targeted and bycatch indicators. Swordfish are distributed widely in the Atlantic Ocean and Mediterranean Sea. There are three management units: Mediterranean group, North Atlantic, and South Atlantic separated at 5 N. Mixing is expected to occur and be highest at the boundary in the tropical zone. The last Atlantic swordfish assessment was conducted in Swordfish spawn in the warm tropical and subtropical waters throughout the year, although seasonality has been reported in some areas. They are found in the colder temperate waters during summer and fall. Because of the broad geographic distribution of the Atlantic swordfish in coastal and off-shore areas, mostly ranging from 50ºN to 45ºS, the species is available to a large number of fishing countries. The ages exploited in the North Atlantic fisheries include primarily ages two and three in recent years. The largest proportion of the Atlantic catches is made using surface drifting longline. However, many additional gears are used, including traditional gillnets off the coast of western Africa. In the North Atlantic estimated catch averaged about tonnes over the last 10 years. In the South Atlantic, catches were generally less than tonnes (with an average value of tonnes) prior to After 1980, landings increased continuously up to a peak of tonnes in 1995, similar to the peak of North Atlantic harvest, due in part to progressive shifts of fishing effort to the South Atlantic. Expansion of fishing activities by southern coastal countries also contributed to this increase in catches. The reduction in catch following the peak in 1995 resulted from regulations and is due in part to a shift to other oceans and target species. The 2006 assessment indicated that North Atlantic swordfish biomass had improved possibly due to strong recruitment in the late 1990s, combined with reductions in reported catch since then, especially compared to the peak catch values of The estimate MSY is about tonnes. The biomass at the beginning of 2006 was estimated to be about 99% of SSBMSY and the 2005 fishing mortality rate was estimated to be about 14% below FMSY. The 2006 assessment for South Atlantic swordfish uses a composite CPUE pattern that has been constructed from directed and by-catch fisheries, which indicates that F is likely below FMSY, and that current SSB is likely above SSBMSY. The 2006 assessment suggested that the Recommendation on catch limits, if fully realized, would lead the northern stock to likely decline to below BMSY. For the southern stock, the 2006 assessment results suggest that biomass is above BMSY and F less than FMSY, but it was unclear whether substantially higher catches than currently envisioned by the Commission could be sustained in the long term.

7 INTERNATIONAL COMMISSION FOR THE CONSERVATION OF ATLANTIC TUNAS (ICCAT) 7 In 2007, the SCRS recommended that the existing TAC ( tonnes), which is close to the estimated MSY ( tonnes), should allow the northern Atlantic swordfish to continue to grow towards BMSY. For the South Atlantic, the SCRS recommended that annual catch should not exceed the provisionally estimated MSY (about tonnes). Mediterranean Swordfish Gradually declining stock biomass of Mediterranean Swordfish has fallen below the level which can support MSY, and fishing mortality has exceeded levels which could support MSY. Mediterranean swordfish is considered to be separate from the Atlantic stocks. Mixing is believed to be low and generally limited to the region around the Straits of Gibraltar. The most recent assessment was conducted in 2007, making use of catch and effort information through Reported catches have fluctuated without trend between 12,000-16,000 tonnes over the last 10 years. Catches are of the same magnitude as those in the north Atlantic, although the area is much smaller. This could be due to higher productivity or lower predation in the Mediterranean. The sharp increase between 1983 and 1988 may be partially attributed to improvement in the national systems for collecting catch statistics. The main fishing gears are surface longline and gillnets, but harpoon, trap and recreational fisheries also report swordfish catches. Following ICCAT recommendations for a general ban of driftnets in the Mediterranean, the gillnet fleet has been decreasing, although the total number of vessels cannot be determined from ICCAT statistics. Production modelling using a long time series of data suggests that the biomass is slightly below BMSY and that F is some 25% above FMSY, while VPA using a shorter time series of data suggest that biomass is less than half BMSY. Based on the VPA results, there is a non-negligible risk that current F could cause rapid declines in the stock. Sailfish Sailfish has a pan-tropical distribution. There are two management units, eastern Atlantic and western Atlantic. The last ICCAT sailfish assessment was conducted in Sailfish are targeted by coastal artisanal and recreational fleets but they are also caught as by-catch by longliners and purse seiners (Figure SAI 1). Catches of sailfish were reported together with spearfish by many longline fleets and, in the statistics, it is not possible to separate the catches of these two species or to distinguish sailfish caches from catches reported as unclassified billfish The 2001 assessments of these two stocks were not considered reliable but there were indications of early decreases in biomass. It is not known if either of the sailfish stocks is fished above FMSY or if the biomass is less than BMSY. There is no basis to provide indications as to the future evolution of catches or of the stocks. The status of the stocks is unknown with respect to exploitation or biomass. It would be prudent to stabilize or reduce fishing mortality, but the paucity of information makes it difficult to quantify any reduction that may be required.

8 8 INTERNATIONAL COMMISSION FOR THE CONSERVATION OF ATLANTIC TUNAS (ICCAT) Small tunas There has been no assessment of small tunas, as there have been problems with data collection. Blue and White Marlin Biomass levels for Blue and White Marlin remain below levels needed to achieve MSY. Between 2001 and 2005 several abundance indicators suggested that the decline in biomass had at least partially halted; other indicators suggest abundance has continued to decline. Biomass levels for White Marlin also remain below levels necessary to achieve MSY, and fishing mortality at a higher rate than that which is necessary to achieve MSY. Combined longline indices and some individual fleet indices suggest the decline has been partially reversed; other indices suggest it has continued to decline. The current management plan has the potential to recover the stocks of blue and white marlin; however, recent increases in catch of Blue Marlin by artisanal fisheries in both sides of the Atlantic may negate the effectiveness of ICCAT s recovery plans. Catches of blue marlin and white marlin continued to decline through Based on the 2006 assessment, the decline in abundance of blue marlin may have slowed or halted, and white marlin may have increased slightly. Recent biomass for blue marlin likely remains well below the BMSY estimated in 2000, F has recently declined and is possibly smaller than Freplacement (which would allow the stock toincrease) but larger than FMSY estimated in the 2000 assessment. Recent biomass for white marlin most likely remains well below the BMSY estimated in the 2002 assessment, F is probably smaller than Freplacement and probably also larger than the FMSY estimated in the 2002 assessment. Blue Shark Biomass for the Blue Shark is believed to be above the amount necessary to support MSY and current harvest levels below the fishing mortality level needed to achieve MSY; however, results are highly uncertain. The biomass of the shortfin mako shark could be below the biomass level that would support MSY, and has been deemed a non-negligible issue. There has been no assessment done as of yet on the porbeagle shark, although a recent study done by Canadian scientists showed that porbeagle stocks have been depleted to levels well below the biomass level needed to support MSY, by as early as Recent fish monitoring information suggests that harvest rates have exceeded sustainable levels and led to further decline in the stock. Rebuilding to MSY levels could require long recovery periods due to the level of depletion and the low intrinsic rate of increase of the stock. Most Atlantic pelagic sharks have very limited biological productivity; a species can be overfished even at very low levels of fishing mortality.

9 INTERNATIONAL COMMISSION FOR THE CONSERVATION OF ATLANTIC TUNAS (ICCAT) 9 Legislative and policy framework Legislation specific to fisheries rebuilding, as well as complementary legislation ICCAT is comprised of contracting parties; any government that is a member of the United Nations (UN), any specialized UN agency, or any intergovernmental economic integration organization constituted by States that have transferred to it competence over matters governed by the ICCAT may join the Commission. Contracting parties of ICCAT include the United States, Japan, South Africa, Ghana, Canada, France (in respect of St. Pierre and Miquelon), Brazil, Morocco, Korea, Cote d Ivoire, Angola, Russia, Gabon, Cape Verde, Uruguay, Sao Tome e Principe, Venezuela, Republic of Equatorial Guinea, Republic of Guinea, United Kingdom (on behalf of its Overseas Territories), Libya, People s Republic of China, Croatia, European Union, Tunisia, Panama, Trinidad & Tobago, Namibia, Barbados, Honduras, Algeria, Mexico, Vanuatu, Iceland, Turkey, Philippines, Norway, Nicaragua, Guatemala, Senegal, Belize, Syria, St. Vincent and the Grenadines, Nigeria, Egypt, Albania, Sierra Leone, Mauritania. Co-operators include Chinese Taipei, Guyana, and the Netherland Antilles. There is also the status of a Cooperating Non-Contracting Party and Fishing Entity. The SCRS is composed of the Species Groups, working groups that assess the status of the various stocks, and two Sub-Committees: Statistics and Ecosystems. Four Panels are responsible for keeping under review the species, group of species, or geographic area under its purview: Panel 1: Tropical Tunas (Yellowfin, Skipjack and Bigeye); Panel 2: Northern Temperate Tunas (Albacore and bluefin); Panel 3: Southern Temperate Tunas (Albacore and Southern Bluefin); and, Panel 4: Other species (Swordfish, billfishes, sharks). The Panels review scientific and other information and make recommendations for joint action by the Contracting Parties aimed at maintaining the stocks at levels that will permit maximum sustainable catches. The Panels may also recommend to the Commission studies and investigations necessary for obtaining information relating to its species, group of species, or geographic area, as well as the co-ordination of research programs by the Contracting Parties. Key terminology and definitions Age of Recruitment: The age when fish are considered to be recruited to the fishery. In stock assessments, this is usually the youngest age group considered in the analyses, typically age 0 or 1. Allocation: The partitioning of fishery controls or fishing rights among participating entities or operating units. For example, the allocation of the TAC into country-specific quotas. Availability: Refers to the distribution of fish of different ages or sizes relative to the distribution of the fishery. Biological Reference Point (BRP): A benchmark against which the abundance of the stock or the fishing mortality rate can be measured in order to determine its status. These reference points can be Limits or Targets, depending on their intended usage. (Caddy and Mahon 1995; Gabriel and Mace 1999; Sissenwine and Shepherd 1987) Biomass: Biomass refers to the abundance of the stock in units of weight. Sometimes, biomass refers to only one part of the stock (spawning biomass, exploitable biomass) but this distinction is not always made.

10 10 INTERNATIONAL COMMISSION FOR THE CONSERVATION OF ATLANTIC TUNAS (ICCAT) Biomass at MSY: A biological reference point. It is the long-term average biomass value expected if fishing at FMSY. The text of the International Convention for the Conservation of Atlantic Tunas states that ICCAT is responsible for studying and appraising information concerning measures and methods to ensure maintenance of the populations of tuna and tuna-like fishes in the Convention area at levels which will permit the maximum sustainable catch and which will ensure the effective exploitation of these fishes in a manner consistent with this catch (Article IV, paragraph 2.b). (Caddy and Mahon 1995) By-catch: Catch of species other than the intended target species in a fishing operation. Bycatch can either be discarded or landed. (Alverson et al. 1994) Carrying Capacity: (1) Virgin biomass. (2) Refers to the holding capacity of a fishing vessel. Catch (C): The total number of fish caught by fishing operations (sometimes catch is used to denote the weight of fish caught). Catch should pertain to all fish killed by the act of fishing, not just those fish that are landed. Catches are reported to ICCAT as part of the Task I data. Catchability (q): The fraction of the stock which is caught by a standardized (effective) unit of effort. It is also used as the constant of proportionality that relates effective effort to fishing mortality (q x f = F) or as the constant of proportionality that relates an index of abundance to absolute stock size (I = q x N). Catchability is affected by fish availability. Thus, specific climatic conditions may result increased or decreased availability of the fish. This would lead to increased (decreased) catchability and, thus, increased (decreased) fishing mortality rate with the same fishing effort. Commercial: Refers to catch or effort that is commercial in nature, typically using industrial-type vessels and gears. Confidence Limits: A statistical measure of uncertainty, providing the lower and upper bounds within which a parameter falls with a given probability. Example: the 80% confidence limits for SSB are the low and high values within which SSB lies with 80% certainty. Controls: Refers to the various controls (measures) that managers can impose to regulate fishing. Controls are usually classified as effort controls or catch controls, depending on what they intend to regulate. (Gulland 1974; Pallarés and Suzuki 1998) Conversion Factors: Multipliers applied to convert landings into Nominal Catches. These factors vary with the species involved and with the dressing of the fish (e.g. fresh, frozen, gutted, etc.,.). They could also vary by country and over time. Discards: Refers to part of the catch that is thrown overboard at sea. Discards may be released either dead or alive. Scientists generally estimate the dead discards as part of the total catch. Estimates of discards can be made in a variety of ways, including samples from observers and logbook records. Fish (or parts of fish) can be discarded for a variety of reasons such as having physical damage, being a non-target species for the trip, and compliance with management regulations like minimum size limits or quotas. EEZ: Exclusive Economic Zone (defined in the Law of the Sea Convention).

11 INTERNATIONAL COMMISSION FOR THE CONSERVATION OF ATLANTIC TUNAS (ICCAT) 11 Effective Effort (f): Measures of fishing effort such as hooks per day of fishing that have been standardized so that the measure is proportional to the fishing mortality rate that the gear(s) impose on the stock of fish. Controls purported to limit effective effort imply that the fishing mortality rate is to be limited. Effort (Fishing Effort, f): A measure of the intensity of fishing operations. How Effort is defined depends on the type of fishery (gear) and often on the type of information available. For longline fisheries, effort is usually defined in units of number of hooks or in hook-hours. For purse-seine fisheries, effort is often defined as boat-days (time fishing plus search time). Scientists should aim to define effort in a way that facilitates effort standardization. Equilibrium: A situation that arises when the fishing mortality, exploitation pattern and other fishery or stock characteristics (growth, natural mortality, recruitment) do not change from year to year. Many yield per recruit analyses assume equilibrium. That is, equilibrium yield per recruit that is computed for a given fishing mortality can be achieved if that fishing mortality is held constant for many years (as many years as there are age classes in the fishery); equilibrium yield per recruit values computed for a new level of fishing mortality or a change in selectivity would not be expected to reach equilibrium until several years from the time of implementation (see Transitional). Other types of stock assessments such as variants of stock production models or catch curves also assume equilibrium. Their non-equilibrium variants aim to better explain the dynamics of the observed data through time. (Hilborn and Walters 1992) Equilibrium Yield Curve: A function that describes the long-term yield which would be obtained at different levels of fishing mortality. At its highest point, the equilibrium yield is the Maximum Sustainable Yield (MSY) and the associated fishing mortality rate is FMSY. (Restrepo et al. 1994) Excess Capacity: In the short-term, it is the fishing capacity over and above that which is needed to extract the TAC from the stock. In the long-term, it is the fishing capacity over and above that which is needed to achieve the management objectives (e.g. to generate a fishing mortality equal to FMSY). Exploitable Biomass: Refers to that portion of a stock s biomass that is available to the fishing gear. Exploitation Pattern: The distribution of fishing mortality over the age composition of the fish, determined by the type of fishing gear and spatial and seasonal distribution of fishing, and by the growth and migration of the fish. In other words, it is the combined effect of gear selectivity and fish availability. The pattern can be changed by modifications to fishing gear; for example, by increasing mesh or hook size or by changing the ratio of harvest by gears exploiting the fish (e.g., gill net, trawl, hook and line). The pattern can also change due to changes in fishing practices such as avoidance of areas where juveniles reside. Exploitation Rate: The proportion of a population at the beginning of a given time period that is caught during that time period (usually expressed on a yearly basis). For example, if 220,000 fish were caught during the year from a population of 1 million fish alive at the beginning of the year, the annual exploitation rate would be Exploitation Ratio: The ratio of fish caught to total mortality (= F/Z).

12 12 INTERNATIONAL COMMISSION FOR THE CONSERVATION OF ATLANTIC TUNAS (ICCAT) F 0.1: A biological reference point. It is the fishing mortality rate at which the increase in equilibrium yield per recruit in weight for an increase in a unit of effort is 10% of the yield per recruit produced by the first unit of effort on the unexploited stock (i.e., the slope of the yield per recruit curve for the F0.1 rate is only 1/10th of the slope of the yield per recruit curve at its origin). [Note: F0.1 is sometimes computed from equilibrium yield curves]. Originally, F0.1 was intended as an economic reference point, measuring where additional investment into effective fishing effort would only produce a 10% marginal gain in yield per recruit. It later evolved into a conservative reference point for yield optimization because F0.1 results in almost as much yield per recruit as Fmax does, but at lower levels of fishing mortality. (Caddy and Mahon 1995) Fmax: A biological reference point. It is the fishing mortality rate that maximizes equilibrium yield per recruit. Fmax is the F level that defines growth overfishing. In general, Fmax is different than FMSY (the F that maximizes sustainable yield), and is usually higher than FMSY, depending on the stock-recruitment relationship. By definition, Fmax is always higher than F0.1. (Caddy and Mahon 1995) FAD (Fish Aggregating Device): Artificial or natural objects placed on the surface that attract several species underneath, thus increasing their catchability. (Kwei and Bannerman 1993; Pallarés et al. 1998) Fecundity: The number of eggs produced on average by a female of a given size/age. Fecundity information is often used to compute spawning potential. Fishing Capacity: Usually refers to the size and characteristics of individual fishing vessels (see Carrying Capacity). Fishing Gears: The equipment used for fishing. Some of the most common fishing gears for tunas and tuna-like fish are baitboat, gillnet, handline, harpoon, troll, haul seine, longline, widwater trawl, purse seine, rod-and-reel, trap, and trawler (see gear codes towards the end of the Glossary). Each of these can have multiple configurations. Fishing Mortality Rate (F): The part of the total mortality rate that is due to fishing. Fishing mortality is usually expressed as an instantaneous rate, as discussed under Mortality Rate, and can range from 0 per year (for no fishing) to high values such as 1.0 or more per year. Fishing mortality should reflect all deaths in the stock that are due to fishing, not just those fish that are actually landed. It is common practice to refer to F as a scalar value but it would be more appropriate to refer to it as a vector. That is, it is important to consider how F is distributed among age groups (i.e. what the exploitation pattern is). For instance, and F value of 0.5 for a stock exploited by purse seines that target small fish would have very different consequences than an F=0.5 for the same stock exploited by longlines targeting large fish. Fishing Pattern: See Exploitation Pattern. Sometimes the term is also used in reference to the way in which fishing operations are conducted. Flag of Convenience (FOC): The term pertains to cases when a boat is registered in a different State than that of ownership, for whatever reasons of convenience. Growth Rate: (1) Intrinsic growth rate: A value that quantifies how much a population can grow between successive time periods. The intrinsic growth rate is often estimated with production models and plays an important role in evaluating the sustainability of different harvest levels. (2) Individual growth rate: A value that quantifies how fast the average individual in the population grows in size or in weight.

13 INTERNATIONAL COMMISSION FOR THE CONSERVATION OF ATLANTIC TUNAS (ICCAT) 13 Landings: The part of the catch that is landed. Limit Reference Point: A benchmark that should not be exceeded with any significant probability according to a given set of management objectives. According to the UNIA, FMSY should be a limit reference point. ICCAT s objectives do not define limit reference points explicitly, although FMSY is the implied target. (Caddy and Mahon 1995) Minimum Size: A control available to managers, intended to minimize the catches of small fish. Such a control is often decided upon based on yield per recruit considerations like avoiding growth overfishing. That is, minimum size regulations aim to alter the exploitation pattern so that young fish are given a better chance to grow before being vulnerable to fishing. Model: A conceptual and simplified idea of how the real world works. Mortality Rate (instantaneous): Conceptually, the easiest way to describe mortality is as a fraction (e.g. 0.3 or 30% of the fish die in a year). Because fishing and natural mortality happen continuously throughout the year, it is not straightforward to use these fractions in an additive way. Expressing these processes as instantaneous rates (i.e. as the fractions that die in infinitesimal periods of time) facilitates the stock assessment analysis computations on an annual basis, even when the catches take place daily. Instantaneous mortality rates of 0.1, 0.5 and 1.0 are equivalent to 10%, 39% and 63% mortality. Natural Mortality Rate (M): The part of the total mortality rate that is due to causes other than fishing (e.g., predation, disease, cannibalism, and perhaps increasingly, environmental degradation such as pollution). These many causes of death are usually lumped together for convenience, because they are difficult to separate quantitatively. Sometimes natural mortality is confounded with losses of fish from the stock due to emigration. M has proven very difficult to estimate, and values are often assumed based on life history characteristics such as longevity. Also, M values are often assumed to remain constant through time and by age. Nominal: Refers to quantities as they are reported, before any analyses or transformations. Nominal catch is the sum of catches that have been reported as round weight or, equivalently, the landings (nominal catches do not include such measures as unreported dead discards). Nominal effort pertains to measures of fishing effort or vessel carrying capacity that have not been standardized. When catchability changes, e.g., through changes in gear technology, trends in nominal effort can give a misleading picture of trends in exploitation. Observer: An independent person that collects information onboard fishing vessels. Observer programs can be used for quantifying bycatch and dead discards, collecting tag returns, etc. (Matsumoto and Miyabe 1999) Overfished: Overfished means that the abundance of the stock is too low. In many fisheries fora the term is used when biomass has been estimated to be below a limit biological reference point that is used as the signpost that defines an overfished condition. ICCAT has not formally defined when a stock is to be categorized as being overfished, so usage of the term may not always be consistent. (Mace 1998) Overfishing: The term generally means that the fishing mortality being exerted on the stock is too high. In many fisheries fora the term is used when F has been estimated to

14 14 INTERNATIONAL COMMISSION FOR THE CONSERVATION OF ATLANTIC TUNAS (ICCAT) be above a limit biological reference point that is used as the signpost that defines overfishing. Usage of the term is not limited to growth overfishing situations; it can also pertain to recruitment overfishing and to other types of overfishing. As with the term Overfished, ICCAT usage of overfishing may not always be consistent. (Mace 1998) Parameter: A quantity that characterizes a population variable in a statistical sense. In population dynamics models, parameters such as the rates of growth, mortality and reproduction provide the essential characteristics of the population. Pelagic: A species that lives in midwater or close to the surface. Tunas and tuna-like fishes are generally referred to as large pelagics. Population: A group of fish of one species which shares common ecological and genetic features. The stocks defined for the purposes of stock assessment and management do not necessarily coincide with self-contained populations. Population Dynamics: In general, refers to the study of fish stock abundance and why it changes over time. Population Model: A component of a stock assessment model, made up of formulations that describe how the population changes from one time period to the next. The types of population models used by ICCAT vary, depending on the species life history and on data availability. Population models can roughly be classified as age/size structured or biomass-based; deterministic or stochastic; density- dependent or density-independent; spatially-structured or spatially aggregated; equilibrium or non-equilibrium. Pop-up Tag: A tag that detaches itself from the fish after a predetermined period of time has elapsed since tagging. After detachment, the tag sends a signal via satellite, providing its position and downloading any other available information (if the pop-up tag is also an archival one). This technology does not rely on the recapturing/reporting of tagged fish to recover the information. (de Metrio et al. 1999) Precautionary Approach: A set of agreed cost-effective measures and actions, including future courses of action, which ensures prudent foresight, reduces or avoids risk to the resource, the environment, and the people, to the extent possible, taking explicitly into account existing uncertaintiesand A population the potential consequences of being wrong" (García, 1996) Production Model: A model that describes, using simple functions, how the population biomass changes from year to year (or, how biomass changes in equilibrium as a function of fishing mortality). The simplest production functions aggregate all of the biological characteristics of growth, natural mortality and reproduction into a simple, deterministic model using three or four parameters. Production models are primarily used in simple data situations, where total catch and effort data are available but agestructured information are either unavailable or deemed to be less reliable (although some versions of production models allow the use of age structured data). (Cadima and Pinho 1996) Quota: A portion of a TAC allocated to a fishery or to an operating unit, such as a size class of vessels or a country. Rebuilding: Refers to the trajectory of a stock from an overfished condition to a defined target. For example, a stock may be rebuilt to the BMSY level.

15 INTERNATIONAL COMMISSION FOR THE CONSERVATION OF ATLANTIC TUNAS (ICCAT) 15 Recruitment: the amount of fish that first become vulnerable to the fishery each year due to growth and/or migration into the fishing area. Recruitment Overfishing: The rate of fishing above which the recruitment to the exploitable stock becomes significantly reduced. This is characterized by a greatly reduced spawning stock, a decreasing proportion of older fish in the catch, and generally very low recruitment year after year. Recruitment overfishing can lead to stock collapse. Spawning Potential Ratio (SPR): The ratio of spawning potential per recruit under a given fishing regime relative to the spawning potential per recruit with no fishing (also known as %MSP for Maximum Spawning Potential). SPR s require information on natural mortality, growth, spawning potential at age and the relative vulnerability by age to fishing. If possible, spawning potential per recruit is measured in fecundity per recruit, but often spawning stock biomass per recruit (SSB/R see below) is an appropriate substitute. SPR and SSB/R are simple extensions to yield per recruit (see below) in that there are two ways in which recruits can be used: they can be caught, in which case they are part of the yield (yield per recruit), or they can survive, in which case they are part of the SPR, SSB/R. SPR is expressed as a ratio of a fished condition to an unfished condition, thus the ratio varies from 0 to 1. Additionally, empirical studies have shown that for some populations SPR s in the order of 20% to 30% may run the risk of recruitment declines, thus there is a basis of comparison between populations. Therefore, FX%SPR fishing mortality rates are sometimes used as biological reference points. (Note: SPR is sometimes used to mean spawners per recruit, but this usage should be avoided and replaced by SSB/R). (Goodyear 1990) Spawning Stock Biomass (SSB): The total weight of sexually mature fish in the population (usually males and females combined, but sometimes female SSB, alone, is used). This quantity depends on the abundance of year classes, the exploitation pattern, the rate of growth, both fishing and natural mortality rates, the onset of sexual maturity, and environmental conditions. Many types of analyses that address reproductive (spawning) potential should use a measure of production of viable eggs (e.g. fecundity). However, when such life-history information is lacking SSB is used as a proxy. Stock: The term has different meanings. In general, a stock is a biological unit of one species forming a group of similar ecological characteristics and, as a unit, is the subject of assessment and management. However, there are many uncertainties in defining spatial and temporal geographical boundaries for such biological units that are 100% compatible with established data collection and geopolitical systems. For this reason, the term stock is often synonym with assessment/management unit, even if there is migration of the same species to and from adjacent areas. Stock Assessment: The application of statistical and mathematical tools to relevant data in order to obtain a quantitative understanding of the status of the stock as needed to make quantitative predictions of the stock s reactions to alternative future regimes. Stock-Recruitment Relationship: A function that describes how recruitment varies with changes in the reproductive output (or biomass) of the parental stock. Two common forms are the Beverton- Holt and the Ricker relationships. The stock-recruitment relationship is particularly important for the understanding of the sustainability of alternative harvesting regimes. Some stock assessment methods incorporate the estimation of such a relationship directly into the model, either explicitly (e.g. some