UPDATED NOMINAL CPUE INDICES AND A PRELIMINARY COMBINED INDEX OF ABUNDANCE FOR THE CANADIAN BLUEFIN TUNA FISHERIES:

SCRS/2015/047 Collect. Vol. Sci. Pap. ICCAT, 72(6): 1412-1428 (2016) UPDATED NOMINAL CPUE INDICES AND A PRELIMINARY COMBINED INDEX OF ABUNDANCE FOR THE CANADIAN BLUEFIN TUNA FISHERIES: 1981-2014 I. Andrushchenko 1 and A.R. Hanke 1 SUMMARY The updated nominal indices of abundance of Atlantic Bluefin tuna from the Canadian rod and reel, tended line and harpoon fisheries show a decrease from 2013 levels. These trends seem linked to a redistribution of fishing effort outside of the geographical scope of the index, as well as a shift in the size composition of the fisheries. A preliminary index of abundance for Bluefin tuna fisheries in Canadian waters is presented, combining the existing two indices with data which has been historically excluded. RÉSUMÉ Les indices nominaux mis à jour de l'abondance du thon rouge de l'atlantique provenant des pêcheries canadiennes de canne et moulinet, de ligne surveillée et au harpon présentent une diminution par rapport au niveau de 2013. Ces tendances semblent liées à une redistribution de l'effort de pêche en dehors de la portée géographique de l'indice ainsi qu'à un changement de la composition des tailles des pêcheries. Un indice préliminaire de l'abondance des pêcheries de thon rouge dans les eaux canadiennes est présenté en combinant les deux indices existants avec des données qui avaient été historiquement exclues. RESUMEN Los índices nominales actualizados de abundancia de atún rojo del Atlántico de las pesquerías canadienses de caña y carrete, barrilete y arpón muestran un descenso respecto a los niveles de 2013. Estas tendencias parecen estar vinculadas con una redistribución del esfuerzo de pesca fuera de la zona geográfica del índice, así como con un cambio en la composición por tallas de las pesquerías. Se presenta un índice preliminar de abundancia en las pesquerías de atún rojo en aguas canadienses, combinando los dos índices existentes con los datos que se han excluido históricamente. KEYWORDS Catch Rates, Size Composition, Bluefin tuna, Rod and Reel 1. Description of the data source 1.1 Description of the fishery and target species The Canadian commercial Bluefin tuna fisheries target bluefin tuna migrating into Canadian waters between the months of July and November. The 2014 spatial distribution of the two main fisheries occurring off the coast of southwestern Nova Scotia (SWNS) and in the southern Gulf of St. Lawrence (sgsl) has remained consistent with that of previous years (Figure 1). Outside of the these two fisheries, catches occur along the east coast of Nova Scotia, with the majority being conducted around St. Margaret s Bay/Halifax and Canso areas (Figure 1). The SWNS fishery generally takes place between the months of August and October, though in recent years the season has been skewed towards October (Figure 2). This fishery continues to be dominated by rod and reel catches, with smaller contributions by tended line and harpoon (Figure 3). The Scotia-Fundy (SF) home fleet continues to account for 80% of the catches in SWNS, due to decreased activity by ex-sector fleets (Figure 4). 1 Fisheries & Oceans Canada, Biological Station, 531 Brandy Cove Road, St. Andrews, NB E5B 2L9 Canada. Email address of lead author: alex.hanke@dfo-mpo.gc.ca. 1412

Similarly, the sgsl fishery season spans the months of August October, with high activity in the later months (Figure 2). The catches are made almost exclusively by rod and reel gear (Figure 3), with the home fleets (GNB, GNS, PQ and PEI) responsible for ~95% of the trips (Figure 4). Fishing activity in NAFO areas 4VW has been historically excluded from both indices (Figure 1). In the 1990s the fishing in 4VW season spanned the months of August through October (Figure 2). More recently, the competitive management structure of the fishery in 4Wd combined with the timing of tuna coming out of the Gulf of St. Lawrence have compressed and delayed the season to the second half of October and into November. 4VW is fished almost entirely by rod and reel gear, though some harpoon catches appear in recent years (Figure 3). The 4VW area is fished by a variety of fleets, with the GNS fleet becoming predominant in the last two years (Figure 4). 1.2 Size, age range and condition of the fish that the index applies to Fish caught in the Southwest Nova Scotia fishery have shown a general increase in round weight throughout the 2000s, up to a series maximum mean weight of 251 kgs in 2013 (25 th and 75 th percentiles at 179 kgs and 319 kgs respectively) (Figure 5). In 2014, the mean weight of the catch decreased to 200 kgs (25 th and 75 th percentiles at 150 kgs and 247 kgs respectively), but remains above the series mean of 172 kgs. The round weight of catch in the southern Gulf of St. Lawrence fishery has remained below the series mean of 350 kgs since 2010 (Figure 5). The mean catch weight for 2014 is the lowest for the series (281 kgs, with 25 th and 75 th percentiles at 228 kgs and 336 kgs respectively), and has been attributed to a particularly strong year class moving through the fishery (Figure 6). Fishermen indicate that a shift in the distribution of larger fish may also contribute to the uncharacteristically low mean weight (see Section 1.5). Recent weight trends in both fisheries are attributed to the redistribution of Bluefin stock components within the Canadian EEZ. This work is currently being explored on a broader geographical scale, and is complemented by fish movements in 4VW and further east in 3LNOP (Figure 7). 1.3 Changes in the fishery that might affect catch rates The mandatory submission of logbooks was instituted in 1996 and the move from a competitive fishery to an Individual Transferrable Quota (ITQ) system began in 2004 for the southwest Nova Scotia fleet. The main fleet fishing in the southern Gulf of St. Lawrence (PEI) adopted an ITQ-like system in 2011. Fishing within 4W is subject to management structure of SWNS, except in 4Wd where the fishery continues to operate in a competitive manner. Historical catches in 4V are subject to restrictions of the sgsl fleet. According to industry feedback, market demand for a given size class of tuna has had some effect on the SWNS fishery s harvest decisions in 2014. Similarly, fishermen from the sgsl fleets have indicated that large bluefin tuna have moved north in the Gulf of St. Lawrence, while the smaller individuals remain in southern waters. 2. Methods 2.1 Data Exclusions and Rationale Both the SWNS and the sgsl datasets were filtered in order to restrict the data to views established in the past. The SWNS fishery index was limited to catches made by tended line, rod and reel and harpoon, excluding catches made by the trapnet fleet in St. Margaret s Bay. Geographically, the data were limited to NAFO areas 4X, 5Y and 5Z (Figure 1, Figure 7), while excluding 4Xm and 4Xu (St. Margaret s Bay / Halifax). Finally, the season for the SWNS index was limited to the months of August, September and October. Similarly, the sgsl index was limited to rod and reel / tended line, and the months of August, September and October. Geographically, sgsl data was bounded by a box of 68 W to 60 W longitude, and 46 N to 50 N latitude (Figure 1, Figure 7). 1413

The combined index was restricted to rod and reel, tended line and harpoon gears, excluding catches made by the trapnet fleet. The index included the months of July through November, and was limited to years 1984 2014. With additional work, the combined index could be expanded to 1981 2014. Catches landed by the Newfoundland fleet (ex-sector) were removed from all datasets because these vessels behave in a manner inconsistent with the other fleets. 2.2 Management Regulations There have been two major changes in the management of the Canadian Bluefin tuna fishery: 1) the introduction of mandatory log submissions in the mid-1990s and 2) the switch to an Individual Transferable Quota (ITQ) fishery in the early 2000s (SWNS, some 4W) and 2010s (sgsl). Starting in 1996, mandatory log submissions provided detailed information on all trips targeting Bluefin tuna in Canadian waters, including trips with no catch; prior to 1996, this information was submitted on a voluntary basis. 2.3 Dataset used in the Analysis A summary of data for the SWNS, sgsl and combined datasets are provided in Table 1-3. 2.3.3 The effort and catch variables In both the SWNS and sgsl nominal indices, hours fished have been used as the measure of effort (Paul et al. 2010), while the catch variable was a count of Bluefin tuna caught, aggregated to trip. For the joint index, the trip-level data by fishing area within the Canadian EEZ produced different catch effort relationships (Figure 8). These differences are largely a function of the fishing behaviors in each area and restrictions imposed on the fishing by management measures. The sgsl (4RST) fishery was limited to a single fish per trip and trips were less than a day long. This is different from SWNS (4X5Z) where trips are multi-day and more fish can be landed per trip. Aggregating catch and effort data from nafo areas 4RST (Gulf of St. Lawrence) by calendar day, gear and port seems to make the catch effort relationship more similar across areas ( Figure 9). Additional measures are being investigated. 2.4 Model Standardization and Diagnostics A negative binomial model, which included year, NAFO area and month, was fit to the combined Bluefin tuna count data, with log (hours fished) as an offset. This preliminary model has patterns in the residuals (Figure 10) and more complicated models addressing this have failed to converge. Additional work is required developing a final model before any conclusions can be drawn. 3. Results 3.1 Nominal Nominal indices of abundance for the SWNS fishery showed a decline in 2014 (Figure 11). The high mean catch weight, thought to have contributed to the index decrease in 2013, has returned to normal levels in 2014, indicating that the redistribution of effort into 4W may have a greater impact on SWNS CPUE than previously thought (Table 3). The sgsl nominal CPUE index has also decreased, but remains far above the levels seen prior to the 2010 season. A combination of a strong year class and movement of larger individuals to feeding grounds in the northern Gulf of St. Lawrence (Baie des Chaleurs) is thought to contribute to this trend. 3.2 Standardized combined index The combined index is a preliminary attempt at generating a single index of abundance for the Canadian Bluefin tuna fisheries. Although this index is subject to the caveats identified within each of the individual indices (management structure, targeting, season fragmentation, etc.), it does successfully address changes in season expansion and effort redistribution into 4W. The area specific indices are shown in Figure 12 and are based on fixing effort at 12 h and month as September. 1414

The standardized index requires additional work before any concrete conclusions can be drawn. 4. Research Recommendations Consideration should be given to estimating the effect of changes in management structure on all three indices, as well as accounting for possible targeting of other tunas in the SWNS fishery (Hanke et al. 2012). It is also important to revisit catch data prior to 1996 to determine the amount the zero-catch trips that should be present in the data. A redistribution of both fishing effort and population components (Hanke et al. 2014) warrants a reanalysis of both the SWNS and sgsl fisheries without the temporal and geographical restrictions historically imposed on these indices. The combined Canadian Bluefin index has potential for addressing the limitations associated with the individual Canadian fisheries indices. Further work into the standardization process is currently underway, and may lead to producing an index on a larger geographical scale. References Hanke, A.R., I. Andrushchenko, and C. Whelan. 2012. Indices of stock status from the Canadian Bluefin Tuna Fishery. SCRS/2012/118. Hanke, A.R., I. Andrushchenko, and C. Whelan. 2014. Indices of stock status from the Canadian Bluefin Tuna Fishery: 1981 to 2013. SCRS/2014/039. Paul, S. D., A.R. Hanke, A.S.M. Vanderlaan, D. Busawon, and J.D. Neilson. 2010. Indices of Stock Status from the 2009 Canadian Bluefin Tuna Fishery. SCRS/2010/070. Zeileis, A and T. Hothorn (2002). Diagnostic Checking in Regression Relationships. R News 2(3), 7-10. URL http://cran.r-project.org/doc/rnews/ 1415

Table 1. Dataset description for the Southwest Nova Scotia bluefin tuna fishery. month hma gear area YEAR AUG SEP OCT GNB GNS PEI PQ SF HP RR TL 4X 5Y 5Z 1988 43 77 0 0 0 2 0 118 0 0 120 101 2 17 1989 169 113 30 27 43 45 25 172 0 1 311 301 17 4 1990 67 127 45 21 18 25 17 158 0 0 239 234 5 6 1991 170 82 71 10 28 85 17 192 0 30 302 333 2 0 1992 84 177 59 11 37 60 12 200 13 8 299 312 9 0 1993 205 305 143 71 117 47 92 326 164 0 489 656 0 4 1994 162 169 3 44 56 55 62 117 72 1 261 322 0 16 1995 208 171 46 55 53 67 45 205 88 7 330 414 2 9 1996 188 33 18 30 33 31 51 94 49 25 165 223 8 10 1997 178 70 9 51 7 20 31 148 81 45 131 261 0 9 1998 232 148 18 66 9 42 27 254 113 132 153 399 2 5 1999 243 74 10 33 16 51 38 189 69 161 97 345 1 0 2000 143 73 61 38 3 41 36 159 40 168 69 285 0 1 2001 209 198 93 41 28 108 45 278 50 332 118 525 4 7 2002 193 255 3 113 102 46 43 147 27 387 37 478 0 3 2003 155 69 0 34 2 26 30 91 21 168 35 222 0 2 2004 86 57 14 1 1 29 12 114 16 75 66 152 0 12 2005 67 87 12 32 1 38 4 91 4 146 16 141 1 29 2006 50 106 10 7 5 10 26 118 7 144 15 155 0 11 2007 43 49 21 9 11 0 9 84 16 88 9 88 9 17 2008 32 69 7 0 12 0 0 96 12 85 11 89 0 19 2009 21 59 6 3 5 0 0 78 4 64 18 77 1 8 2010 32 57 5 6 11 0 0 77 4 77 13 84 2 9 2011 24 54 15 3 8 0 0 82 3 73 17 87 1 7 2012 46 24 44 1 13 0 0 100 6 101 7 104 2 10 2013 23 32 57 0 10 0 0 102 18 64 30 107 1 4 2014 19 28 33 0 10 0 0 70 7 59 14 79 1 0 1416

Table 2. Dataset description for the southern Gulf of St. Lawrence bluefin tuna fishery. month hma gear YEAR AUG SEP OCT GNB GNS PEI PQ SF RR TL 1981 920 746 90 0 0 1761 0 0 0 1756 1982 4632 2007 1 0 0 6640 0 0 0 6640 1983 1292 2569 1398 0 0 5306 0 0 0 5259 1984 703 1881 841 228 365 2789 15 28 52 3373 1985 1006 1316 386 150 39 2493 0 26 0 2708 1986 511 523 176 37 23 1145 0 5 34 1176 1987 141 161 35 23 0 304 0 0 0 337 1988 233 228 35 39 19 438 0 0 2 494 1989 188 165 60 19 18 376 0 0 8 405 1990 508 614 209 12 11 1306 0 0 185 1146 1991 143 179 167 7 25 433 0 24 43 447 1992 122 454 241 3 32 776 0 0 81 736 1993 176 574 584 54 186 1096 0 0 272 1064 1994 807 1823 67 22 308 2271 0 95 651 2046 1995 811 1341 906 3 1151 1801 1 2 981 2130 1996 3519 4658 3408 187 3103 7420 138 680 6892 4693 1997 2149 2734 2731 75 2546 4983 0 10 5603 2011 1998 1062 2336 1292 64 1422 3199 5 0 3567 1123 1999 1085 2816 292 39 1137 3017 0 0 3492 701 2000 2843 2601 1739 116 2063 4979 25 0 6656 527 2001 3440 1391 1259 94 1720 4233 43 0 5777 313 2002 3798 2697 10 178 1774 4508 45 0 6163 343 2003 4372 902 0 285 1140 3801 49 0 5020 257 2004 2973 895 16 120 1550 2103 109 2 3824 60 2005 4114 1033 42 381 1413 3285 110 0 5062 128 2006 4972 1068 388 265 1195 4730 238 0 6353 75 2007 993 555 444 55 353 1320 246 19 1956 37 2008 1449 136 1425 146 582 1953 288 41 2945 65 2009 1040 209 922 39 365 1514 234 19 2144 27 2010 50 181 482 0 163 476 50 24 705 8 2011 246 414 381 63 262 630 53 33 1023 19 2012 116 582 343 71 266 611 57 36 1007 34 2013 78 704 279 95 197 695 48 26 1029 33 2014 104 679 416 127 268 716 27 61 1170 29 1417

Table 3. Dataset description for the combined index of abundance for the Canadian bluefin tuna fishery. month hma gear area management YEAR JUL AUG SEP OCT NOV GNB GNS PEI PQ SF HP RR TL 3LNOP 4RST 4VW 4X5YZ COMP ITQ 1984 0 333 995 305 36 140 148 1381 0 0 0 59 1610 0 1669 0 0 1669 0 1985 0 976 1281 361 3 150 42 2429 0 0 0 0 2621 0 2621 0 0 2621 0 1986 0 511 518 176 1 37 23 1146 0 0 0 34 1172 0 1206 0 0 1206 0 1987 0 138 155 34 0 23 0 304 0 0 0 0 327 0 327 0 0 327 0 1988 2 243 258 35 4 39 19 431 0 53 0 2 540 0 487 0 32 519 0 1989 2 299 236 80 0 32 52 391 20 122 0 8 609 0 387 0 179 592 0 1990 5 822 1336 869 16 52 123 2451 15 407 0 1737 1311 0 1058 194 168 2748 0 1991 9 586 666 348 2 17 174 1048 13 359 0 900 711 0 429 65 177 1387 0 1992 22 586 1103 554 7 13 177 1670 13 399 11 1220 1041 0 753 96 210 1991 0 1993 0 392 901 729 4 125 313 1154 91 343 156 325 1545 0 1312 10 371 1858 0 1994 105 1159 2164 65 10 62 385 2683 52 321 51 1094 2358 0 2615 149 247 3368 0 1995 18 999 1510 925 47 50 1206 2013 40 190 71 1153 2275 0 2955 0 0 3311 0 1996 64 3971 5418 4668 209 270 3662 8782 203 1413 189 9041 5100 0 9866 1943 221 13388 0 1997 220 2703 4374 3881 169 392 3156 6718 239 842 147 8818 2382 1 7339 259 241 10707 0 1998 95 1789 4004 3121 320 340 2654 5408 137 790 138 7844 1347 2 4488 594 262 8786 0 1999 85 1675 3942 952 0 196 2071 3894 107 386 77 5745 832 0 4179 507 270 6508 0 2000 216 3186 3115 2452 115 388 2801 5482 79 334 46 8423 615 0 7256 349 197 8909 0 2001 194 3615 1944 1751 0 287 1998 4753 110 356 39 7072 393 2 6117 457 291 7375 0 2002 271 4232 3227 8 0 305 2094 4927 134 278 44 7490 204 1 6549 438 210 7653 0 2003 1091 4499 1007 0 0 385 1163 4733 88 228 53 6351 193 3 6096 134 175 6529 0 2004 750 3051 1385 86 0 396 1542 2781 228 325 46 5077 149 1 4500 171 130 4981 119 2005 13 4193 1635 313 3 659 1607 3292 321 278 23 5983 151 1 5079 272 118 5907 92 2006 217 4955 1825 533 7 447 1756 4669 299 366 22 7418 97 18 6451 342 149 7226 118 2007 359 989 657 960 39 168 589 1611 314 322 16 2931 57 2 2252 234 88 2740 91 2008 349 1441 282 1947 140 337 824 2307 280 411 15 4064 80 0 3223 254 99 3830 117 2009 1 1019 342 1025 3 72 396 1461 213 248 12 2327 51 5 2087 85 74 2197 86 2010 3 81 271 559 31 22 184 462 49 228 10 909 26 8 689 60 85 766 89 2011 24 267 457 463 143 84 329 642 52 247 7 1311 36 0 1033 55 76 36 1193 2012 5 151 600 521 69 100 337 585 53 271 8 1298 40 0 1018 65 89 24 1197 2013 15 100 803 440 14 137 293 699 48 195 19 1290 63 0 1056 51 94 24 1290 2014 0 119 730 556 79 164 374 707 27 212 11 1428 45 2 1194 77 67 26 1375 1418

Figure 1. Historic distribution of trips in the Southwest Nova Scotia(SWNS) and Southern Gulf of St. Lawrence (sgsl) bluefin fisheries between 1981 and 2013, in multi-year intervals; bottom panel is limited to the 2014 season. Blue polygons show historic NAFO area limitations for each fishery. 1419

Figure 2. Season progression using proportion of trips by month within a given year in the Southwest Nova Scotia (top) and Gulf St. Lawrence (middle) and 4VW (bottom) Bluefin tuna catch data. The month restriction has been relaxed and the solid line indicates switch from competitive to an ITQ-like structure in each fishery. Dashed line indicates when some vessels switched to ITQ. 1420

Figure 3. Relative frequency of records gears (tended line, rod and reel, harpoon) within year for the Southwest Nova Scotia (top) and Gulf St. Lawrence (middle) and 4VW (bottom) bluefin tuna fisheries. Historic restrictions apply. 1421

Figure 4. Relative frequency of records by year and home management areas (fleets) within year for Southwest Nova Scotia (top) and Gulf St. Lawrence (middle) and 4VW (bottom). Historic restrictions apply. 1422

Figure 5. Round weight (kg) of recent catches made in the Southwest Nova Scotia (top) and Gulf of St. Lawrence (bottom) bluefin fisheries. Red line indicates series mean. 1423

Figure 6. Catch composition for the sgsl fishery since 1995. Vertical line marks series mean (1981-2014) of 350 kgs. 1424

Figure 7. Map delimiting major NAFO areas within the Canadian EEZ. 1425

Figure 8. Relationship between effort (hours fished) and catch (number of Bluefin tuna) for each unique fishing area where effort and catch for 4RST is aggregated to the trip level. Red dots represent the mean number of hours required to catch each discrete number of fish (0 to 30). Figure 9. Relationship between effort (hours fished) and catch (number of Bluefin tuna) for each unique fishing area where effort and catch for 4RST is aggregated to calendar day by gear and port. Red dots represent the mean number of hours required to catch each discrete number of fish (0 to 30). 1426

Figure 10. Plots of standardized residuals from the combined index model. 1427

Figure 11. Nominal CPUE indices for SWNS and sgsl fisheries. Figure 12. Preliminary standardized indices and 95% CIs for Canadian fishing areas. The points are the nominal values. 1428